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Background: Large colon volvulus is a cause of colic in horses with high morbidity and mortality when not promptly treated. More treatment options are needed to improve the outcome of these cases by protecting against the damage caused by ischaemia and reperfusion injury., Objectives: To determine the effect of preconditioning with dexmedetomidine prior to induction of ischaemia-reperfusion (IR) injury in a large colon volvulus model in the horse., Study Design: Randomised blinded in vivo experiments., Methods: Horses received either a dexmedetomidine (DEX) or saline (CON) constant rate infusion (CRI) immediately following induction of anaesthesia. Venous, arterial, and transmural occlusion of a section of the large colon was performed for 3 h, after which the ligatures and clamps were removed to allow for reperfusion for 3 h. Biopsies of the large colon were taken at baseline, 1 and 3 h of ischaemia, and at 1 and 3 h of reperfusion., Results: The severity of crypt epithelial loss (DEX = 2.1 [0.8-2.8], CON = 3.1 [2.5-4], p = 0.03) and mucosal haemorrhage was decreased (DEX = 2.1 [1.3-3], CON = 3.5 [2.5-4], p = 0.03) in group DEX compared to group CON when graded on a scale of 0-4. Crypt length remained longer (DEX = 369.5 ± 91.7 μm, CON = 238.5 ± 72.6 μm, p = 0.02) and interstitium to crypt (I:C) ratio remained lower (DEX = 1.4 (1-1.7), CON = 2.6 [1.8-5.9], p = 0.03) in group DEX compared to group CON during reperfusion., Main Limitations: Clinical applicability of pharmacologic preconditioning is limited., Conclusion: Preconditioning with a dexmedetomidine CRI prior to IR injury demonstrated a protective effect histologically on the large colon in the horse. Further investigation into postconditioning with dexmedetomidine is warranted as a possible intervention in colic cases suspected of being large colon volvulus., (© 2024 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Ancillary diagnostic methods to enhance the accuracy of viability assessment have not been established for use in clinical practice., Objectives: To assess intestinal microperfusion measured by Laser Doppler Flowmetry and Spectrophotometry (LDFS) in naturally occurring small intestinal strangulations of different origins and to compare this between viable and non-viable segments., Study Design: Prospective clinical trial., Methods: Forty horses undergoing colic surgery for naturally occurring small intestinal strangulations were included. Tissue oxygen saturation (tSO 2 ), haemoglobin (tHB) and blood flow (tBF) were determined by LDFS before and after release of the strangulation. Intestinal biopsies were taken in cases that underwent intestinal resection or intraoperative euthanasia and assessed using a semi-quantitative mucosal injury score (MIS). The LDFS measurements were compared between the different categories of strangulation causes and histopathological injury using parametric and non-parametric tests (p < 0.05)., Results: Strangulations by pedunculated lipomas had lower tBF (13.9 ± 18 arbitrary units [AU]) than epiploic foramen entrapments (65.2 ± 61 AU; CI -1.697 to -0.2498; p = 0.005). Segments with MIS > 5 showed lower tBF during strangulation than segments with MIS < 4 (mean difference 61.1 AU; CI -1.119 to -0.07361; p = 0.03). This did not differ significantly following release of strangulation. Furthermore, there was a positive correlation between the inflammatory cell count and tBF during strangulation (r 0.34; CI 0.01 to 0.60; p = 0.04). The tSO 2 and tHB did not differ between the different categories of lesions or injury., Main Limitations: No biopsies could be taken from the intestinal segments that did not undergo resection. The duration of strangulation could not reliably be ascertained., Conclusions: Blood flow measurements in naturally occurring strangulating lesions show a varying degree of ischaemia in different causes of strangulation. Intestinal blood flow measurements prior to release of the strangulation could potentially contribute to the identification of mucosal injury, yet a high individual variability and other contributing factors need to be considered., (© 2024 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Palmar/plantar osteochondral disease (POD) of the metacarpal/tarsal condyles is a common pathological finding in racehorses., Objective: To compare diagnoses, imaging details, and measurements of POD lesions between cone-beam computed tomography CT (CBCT), fan-beam CT (FBCT), and low-field magnetic resonance imaging (MRI) using macroscopic pathology as a gold standard., Study Design: Cross-sectional study., Methods: Thirty-five cadaver limbs from 10 horses underwent CBCT, FBCT, MRI, and macroscopic examination. CT and MR images were examined for presence of POD, imaging details of POD, and measurements of POD dimensions and areas. Imaging diagnoses, details, and measurements were compared with macroscopic examination and between modalities., Results: Forty-eight POD lesions were seen over 70 condyles. Compared with macroscopic examination the sensitivity and specificity of diagnosis were 95.8% (CI95 = 88%-99%) and 63.6% (CI95 = 43%-81%) for FBCT, 85.4% (CI95 = 74%-94%) and 81.8% (CI95 = 63%-94%) for CBCT, and 69.0% (CI95 = 54%-82%) and 71.4% (CI95 = 46%-90%) for MRI. Inter-modality agreement on diagnosis was moderate between CBCT and FBCT (κ = 0.56, p < 0.001). POD was identified on CT as hypoattenuating lesions with surrounding hyperattenuation and on MRI as either T1W, T2*W, T2W, and STIR hyperintense lesions or T1W and T2*W heterogeneous hypointense lesions with surrounding hypointensity. Agreement on imaging details between CBCT and FBCT was substantial for subchondral irregularity (κ = 0.61, p < 0.001). Macroscopic POD width strongly correlated with MRI (r = 0.81, p < 0.001) and CBCT (r = 0.79, p < 0.001) and moderately correlated with FBCT (r = 0.69, p < 0.001). Macroscopic POD width was greater than all imaging modality (p < 0.001)., Main Limitations: Effect of motion artefact in live horse imaging could not be assessed., Conclusions: All imaging modalities were able to detect POD lesions, but underestimated lesion size. The CT systems were more sensitive, but the differing patterns of signal intensity may suggest that MRI can detect changes associated with POD pathological status or severity. The image features observed by CBCT and FBCT were similar., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Transrectal ultrasonography is the best technique for evaluating the ventral aspect of the lumbosacral and sacroiliac regions yet this diagnostic technique does not always lead to a final diagnosis of back pain in horses., Objectives: To describe anatomical variations and acquired pathological bony changes (APBCs) in the lumbosacral and sacroiliac regions detected by ultrasonography (US) and computed tomography (CT) examinations on specimens. We hypothesised that age, body mass, previous use and anatomical variations may be correlated with the presence and/or severity of APBCs., Study Design: Descriptive cadaver study., Methods: Lumbosacroiliac specimens were obtained from 51 horses that died or were euthanised for reasons other than the study and underwent US and CT examinations post-mortem., Results: Forty-two specimens were analysed. The most prevalent lumbosacral disc morphology was type 2 (21/42), and protrusions were found in 15/42 specimens. Abnormal echogenicity of the L5-L6 and lumbosacral discs was detected in 11/42 and 30/42 specimens, respectively. Abnormalities in the size of the L5-L6 disc were found in 10/42 specimens and correlated with promontorium localisation (Cramér's V coefficient [V] = 0.42) and lumbosacral disc morphology (type 1: V = 0.41; type 5: V = 0.69). The most prevalent orientation of the L6 spinous process (SP) was convergent (24/42). The promontoria were mostly located between L6 and S1 (36/42). Lumbosacral spondylosis was detected in 24/42 specimens and spondylolisthesis in one. Age was associated with the severity of APBCs in the sacroiliac joints, lumbosacral intertransverse joints, articular process joints, spondylosis and L6 or S1 bone plate irregularities. Lumbosacral spondylosis or L6 extremitas caudalis irregularity was associated with lumbosacral angulation, variability in the size of the L5-L6 disc and localisation of the promontorium, L6 SP orientation and L6 extremitas caudalis irregularity with abnormal echogenicity of the LS disc., Main Limitations: Lack of information on clinical signs., Conclusions: High variability and prevalence of the anatomical variations and APBCs in the lumbosacroiliac region were observed, and correlations between some anatomical variations and APBCs and between APBCs and age were reported., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Desmitis of the accessory ligament of the deep digital flexor tendon (ALDDFT) is a commonly reported injury. Despite the commonality of this injury, the literature is limited to small case series, with the reported success following treatment varying from 18% to 75%., Objectives: To identify the prognosis and factors associated with a return to work following ALDDFT injury., Study Design: Retrospective case series., Methods: Medical records of horses from four equine hospitals (January 2000 and December 2018) with a diagnosis of desmitis of ALDDFT were reviewed. Data retrieved included case detail, use, history, lameness treatment and follow-up. Success was defined as returning to work. Backward stepwise logistic regression was used to identify variables significantly associated with return to work., Results: Ninety-one horses were included. The mean age was 13.5 years (standard deviation 4.9 years). Thirty-four percent (28/91) of horses were sound at the initial presentation. Sixty-eight percent (62/91) of horses were managed using controlled exercise alone, 28% (29/91) were treated with intra-lesional injection, therapeutic ultrasound, extracorporeal shockwave therapy or desmectomy of the ALDDFT and 3% (3/91) were euthanased without treatment. Sixty-four percent (54/85) of horses returned to work. Horses that were lame at follow-up were less likely to return to work (odds ratio [OR] 107.93, 95% confidence interval [CI] 20.06-580.61, p < 0.001) than those that returned to soundness. Identification of adhesions on ultrasonography was also associated with having reduced odds for return to work when compared to horses without adhesions (OR 0.10, 95% CI 0.01-0.76, p = 0.03)., Main Limitations: Retrospective nature of the study, the potential of selection bias with regards to follow-up., Conclusion: Sixty-four percent (54/85) of horses returned to work following injury of the ALDDFT. Persistence of lameness and adhesion formation were significantly associated with a poor outcome., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Clinicopathological findings and their association with the outcome and development of laminitis in horses with acute diarrhoea has not been investigated in a multicentre study across different geographic regions., Objectives: Describe and compare clinicopathologic findings of diarrhoeic horses between different geographic regions, survival rates and factors associated with non-survival and laminitis., Study Design: Multicentre retrospective case series., Methods: Information from horses with acute diarrhoea presenting to participating institutions between 2016 and 2020 was collected, and clinicopathological data were compared between surviving and non-surviving horses and horses that did and did not develop laminitis. Survival rates and seasonal and geographic differences were also investigated., Results: One thousand four hundred thirty-eight horses from 26 participating institutions from 4 continents were included; 76% survived to discharge with no differences identified between geographic regions. The survival proportion of horses with SIRS and creatinine concentrations > 159 μmol/L was 55% (154/279) compared with 81% (358/437) for those with SIRS and creatinine concentrations < 159 μmol/L (p < 0.001). The survival proportion of horses with SIRS that had an L-lactate concentration > 2.8 mmol/L was 59% (175/298) compared with 81% (240/296) in horses with SIRS and L-lactate concentration < 2.8 mmol/L (p < 0.001). The proportion of horses that developed laminitis was lower in Europe (4%, 19/479) compared with North America (8%, 52/619), Australia (8%, 12/138) and Latin America (11%, 16/146) (p < 0.05). More horses developed laminitis in the summer (46%, 39/85) compared with winter (18%, 15/85), spring (18%, 15/85) and fall (19%, 16/85) (p < 0.01). Horses with laminitis had greater odds of non-survival than those without laminitis (OR: 3.73, 95% CI: 2.47-5.65)., Main Limitations: Not all variables were available for all horses due to the retrospective nature., Conclusions: Clinicopathological findings in horses with acute diarrhoea and their association with survival are similar across geographic regions. However, developing laminitis secondary to diarrhoea is less common in Europe. In addition, factors associated with non-survival were indicative of disease severity and subsequent cardiovascular compromise., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Data on equine lumbar pathology hardly exist in breeds other than Thoroughbreds., Objectives: To describe pathological changes of the osseous lumbar vertebral column in Warmblood horses, Shetland ponies and Konik horses., Study Design: Descriptive post-mortem study., Methods: The lumbar vertebral columns of 34 Warmblood horses, 28 Shetland ponies, and 18 Konik horses were examined by computed tomography (CT). Osteoarthritis (OA) of articular processes (APJs), OA of intertransverse joints (ITJs), intervertebral disc (IVD) mineralisation, impingement of spinous (SPs) and transverse (TPs) processes and spondylosis were scored. Breed differences in prevalence and severity of pathologies were analysed by linear regression analysis and by calculating Spearman's rank correlation coefficients (r s )., Results: In Warmblood horses, the prevalence of OA of APJs, impingement of SPs and TPs was respectively 90%, 36%, and 35%, significantly higher than in the other breeds (p < 0.001). In Konik horses, IVD mineralisation (40%) and spondylosis (10%) were more frequent than in Warmbloods and Shetland ponies (p = 0.03). Severity score for OA of ITJs was highest in Shetland ponies (p < 0.001). For impingement of SPs, severity score was highest in Warmbloods (p = 0.03), and of TPs lowest in Shetland ponies (p = 0.003). For all parameters, except for spondylosis in Shetland ponies, there was a positive correlation between percentage of vertebrae affected and age, with IVD mineralisation scores increasing faster in Konik horses (p < 0.001). In all breeds, there was also a positive relation between scores of severity and age for OA of APJs and ITJs and for IVD mineralisation, with severity scores increasing faster in Shetland ponies (p = 0.04). Strong left/right correlations of the severity scores were seen for OA of the APJ, ITJ, impingement of TPs, and paramedian spondylosis (r s  = 0.74-0.86, all p < 0.001)., Main Limitations: Clinical histories were not available., Conclusions: There are distinct breed differences between prevalence and severity of osseous pathologies of the lumbar spine. Warmblood horses have higher scores for most pathologies with IVD mineralisation being more important in Konik horses and OA of ITJs in Shetland ponies., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Focal hyperintense lesions within the navicular bursa emanating from the dorsal border of the deep digital flexor tendon (DDFT) can be recognised on T1-weighted magnetic resonance images (MRI) and have been attributed to lameness in horses. Removal of these lesions, also referred to as synovial masses, by navicular bursoscopy is currently recommended., Objectives: To investigate the correlation between MRI and navicular bursoscopic findings. It is hypothesised that the prognosis following surgery is proportional to the size of the DDFT lesion., Study Design: Retrospective analysis of clinical records., Methods: Horses undergoing standing low-field MRI and navicular bursoscopy with >1 year follow-up were included. A grading system was developed to classify the size of synovial mass(es) and lesion(s) of the DDFT on MRI and at surgery. Generalised estimating equations were used to evaluate the association between MRI findings and surgery and between outcome and severity of the tendon injury., Results: Fifty-nine horses presenting over a 15-year period (2006-2021) fulfilled inclusion criteria. Ninety navicular bursae were examined both on MRI and endoscopically. There was strong correlation between the size of synovial masses and tendon lesions on MRI and bursoscopy (p < 0.001, OR: 25.61, 95% CI 8.71-75.29 and p < 0.001, OR: 7.34, 95% CI 2.70-19.92, respectively). Size of tendon lesion and synovial mass had no impact on prognosis (p = 0.3, OR: 1, 95% CI 1-1 and p = 0.1, OR: 1, 95% CI 1-1, respectively), which was guarded (30.5% return to previous level of exercise)., Main Limitations: Performance data for conservatively treated horses with MRI-detected synovial masses was not considered, nor was the effect of navicular bursal effusion. Horses were not randomly assigned to treatment protocols., Conclusion: There is good correlation between MRI and bursoscopic findings of DDFT lesions and synovial masses within the navicular bursa, with no false positives. Size of the synovial masses and DDFT lesions does not influence prognosis following navicular bursoscopy., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Non-septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse., Objectives: To review the published literature to determine which tendon sheaths are commonly affected by non-septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non-septic tenosynovitis., Study Design: Systematic review., Methods: Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. The inclusion criteria followed a participants, interventions, comparisons, outcome and study design (PICOS) approach. For inclusion, studies had to include live equids with non-septic tenosynovitis of any tendon sheath. Studies were excluded if they only described non-equine species, if they included data only on non-tendon sheath structures, or if they included data exclusively on cases of septic or contaminated tendon sheaths. Determination of non-sepsis relied on the diagnosis of the original authors; however, if non-sepsis was not explicitly specified, then cases that had a history of contamination of the sheath, a wound near the sheath or a positive bacterial culture were excluded from analysis. Data analysed included the distribution of structures affected by non-septic tenosynovitis, the most common pathological lesions identified within each sheath, and the most frequently reported surgical complications of non-septic tenosynovitis. The quality of each study was assessed using a methodological quality analysis., Results: A total of 85 studies describing non-septic tenosynovitis in the horse were included. Across all 85 studies, there were a total of 2449 tendon sheaths in 2101 horses reported to be affected by non-septic tenosynovitis. The digital flexor sheath was the most reported structure to be diagnosed with non-septic tenosynovitis: 41/85 (48%) studies examined the digital flexor sheath exclusively, followed by the carpal flexor sheath, tarsal flexor sheath, carpal extensor sheaths, tarsal extensor sheaths, and one case of biceps brachii non-septic tenosynovitis. For most tendon sheaths, the most common pathological lesion was an intrathecal tear of a soft tissue structure, including tears of the deep digital flexor tendon and tears of the manica flexoria. Bilateral disease was most common in the carpal flexor sheath, where distal radial physeal exostoses were the most common pathological lesions. Less common causes of non-septic tenosynovitis included neoplasia, fracture of a bone adjacent to a tendon sheath, and mineralisation of an intrathecal tendon. The likelihood of return to previous level of athletic function following non-septic tenosynovitis of most structures was approximately 50%, and the most common complication was persistent effusion following tenoscopy. While iatrogenic infection following surgery was uncommon, it was most likely following tenoscopy of the digital flexor sheath., Conclusion: Non-septic tenosynovitis is commonly reported in equine athletes, with intra-thecal tears of the deep digital flexor tendon, superficial digital flexor tendon and manica flexoria frequently reported. Directions for future research include more thorough assessment of and reporting of complications following non-septic tenosynovitis and correlation of characteristics of intrathecal pathological lesions with clinical outcomes., (© 2023 EVJ Ltd.)

Background: Vulvar squamous cell carcinoma (VSCC) has been recently associated with Equus caballus papillomavirus type 2 (EcPV2) infection. Still, few reports concerning this disease are present in the literature., Objective: To describe a case of naturally occurring EcPV2-induced VSCC, by investigating tumour ability in undergoing the epithelial-to-mesenchymal transition (EMT)., Study Design: Case report., Methods: A 13-year-old Haflinger mare was referred for a rapidly growing vulvar mass. After surgical excision, the mass was submitted to histopathology and molecular analysis. Histopathological diagnosis was consistent with a VSCC. Real-time qPCR, real-time reverse transcriptase (RT)-qPCR and RNAscope were carried out to detect EcPV2 infection and to evaluate E6/E7 oncogenes expression. To highlight the EMT, immunohistochemistry (IHC) was performed. Expression of EMT-related and innate immunity-related genes was investigated through RT-qPCR., Results: Real-time qPCR, RT-qPCR and RNAscope confirmed EcPV2 DNA presence and expression of EcPV2 oncoproteins (E6 and E7) within the neoplastic vulvar lesion. IHC highlighted a cadherin switch together with the expression of the EMT-related transcription factor HIF1α. With RT-qPCR, significantly increased gene expression of EBI3 (45.0 ± 1.62, p < 0.01), CDH2 (2445.3 ± 0.39, p < 0.001), CXCL8 (288.7 ± 0.40, p < 0.001) and decreased gene expression of CDH1 (0.3 ± 0.57, p < 0.05), IL12A (0.04 ± 1.06, p < 0.01) and IL17 (0.2 ± 0.64, p < 0.05) were detected., Main Limitations: Lack of ability to generalise and danger of over-interpretation., Conclusion: The results obtained were suggestive of an EMT event occurring within the neoplastic lesion., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Acetaminophen is used clinically in horses with musculoskeletal pain; however, no studies have been performed in horses with chronic lameness., Objectives: To determine the pharmacokinetics, safety and efficacy of chronic dosing of acetaminophen in horses with naturally occurring chronic lameness., Study Design: Longitudinal., Methods: Twelve adult horses with chronic lameness were treated with acetaminophen (30 mg/kg PO) every 12 h for 21 days. Plasma concentrations of acetaminophen were analysed on days 7 and 21 via LC-MS/MS and noncompartmental pharmacokinetic analysis. Lameness was evaluated by body-mounted inertial sensor (BMIS) and 10-point subjective lameness score on day 21 and compared to untreated baseline evaluation on day 35. Clinicopathological analysis (n = 12), hepatic biopsy (n = 6) and gastroscopy (n = 6) were evaluated on days -1 and 22., Results: Maximum plasma acetaminophen concentration (C max ) was 20.83 ± 10.25 μg/mL at time (T max ) 0.40 ± 0.22 h on day 7. The C max on day 21 was 17.33 ± 6.91 μg/mL with a T max of 0.67 ± 0.26 h. Subjective lameness scores significantly improved at 2 and 4 h post-treatment; Significant percent improvement was detected in PD max for horses with hindlimb lameness at 1, 2 and 8 h post-treatment. There were no significant differences in gastroscopy or hepatic biopsy scores between days -1 and 22., Main Limitations: Small sample size, multi-limb lameness of varying severity and aetiology, lack of intermediary lameness evaluation., Conclusions: In horses with naturally occurring chronic lameness, acetaminophen at 30 mg/kg produced a transient improvement in subjective lameness and BMIS evaluation. Acetaminophen may not be effective as a monotherapy. Acetaminophen was safe following 21 days of 30 mg/kg PO every 12 h, with no evidence of clinically significant changes in clinicopathological analysis, hepatic biopsy or gastric ulceration scores., (© 2023 EVJ Ltd.)

Background: Osteochondrosis dissecans (OCD) is common in the femoropatellar joint in Thoroughbred yearlings for sale at auction and there is no consensus on the effect on racing outcomes., Objectives: Describe femoropatellar OCD in juvenile Thoroughbreds and compare the racing performance of affected Thoroughbred horses to siblings and unaffected horses from the same sale., Study Design: Retrospective case-control study of juvenile horses born 2010-2016., Methods: Radiographic reports from 27 Thoroughbred auctions of weanling (5-11 months of age) and yearling (12-22 months of age) horses were reviewed to identify femoropatellar OCD. Age and sex of cases and controls were obtained from the sales catalogue. Racing performance was obtained from an online database. Correlation between lesion characteristics and racing performance were assessed using Pearson and Spearman correlations for continuous and ordinal/categorical variables respectively. Racing performance was compared between cases and sibling controls and age- and sex-matched sale number controls from the same sale with Poisson distribution and log link. Significance level of alpha = 0.05 was used., Results: Femoropatellar OCD was identified in 429 horses with North American race records. OCD was present on 519 lateral trochlear ridges and 54 medial trochlear ridges. There were more males in the case group (70%) than in the sibling control group (47%). Case racing performance was compared to 1042 sibling and 757 hip controls. There were significant but small decreases in racing metrics of cases and increases in males for years raced, total starts, starts for 2-5 years of age, total placings, and placings at 2-4 years of age. Analysis of specific lesion metrics revealed weak correlations for performance outcomes (positive and negative) resulting in an inability to draw firm conclusions., Main Limitations: Retrospective study where case management was unknown., Conclusions: Femoropatellar OCD in juvenile Thoroughbreds for sale at auction decreases some racing outcomes., (© 2023 EVJ Ltd.)

Background: Subchondral lucencies (SCLs) in the distal aspect of the medial femoral condyle (MFC) of young Thoroughbred horses are a source of controversy on presale radiographs. There is limited scientific evidence regarding the risk of progression and impact on future racing performance., Objectives: To (1) identify the prevalence of MFC SCLs on sales repository radiographs in yearling and 2-year-old Thoroughbreds; (2) identify any association between grade of MFC SCL and future racing performance and (3) monitor changes in MFC SCL grades between yearling and 2-year-old sales., Study Design: Prospective cohort study., Methods: Radiographs were obtained with consignor permission from a 2016 yearling sale and five 2017 2-year-old sales. Stifle radiographs were evaluated and MFC SCLs graded on a scale of 0-3. Axial MFC lucencies were recorded separately. Maximum MFC grades per horse were analysed for associations with racing performance outcomes, adjusted for sex, to the end of the horses' 4-year-old racing year. Analysis was via logistic, negative binomial or linear regression as appropriate, with the threshold for significance set at α = 0.05., Results: Radiographs from 2508 yearlings (5016 stifles) and 436 2-year-olds (872 stifles) were included in the study. MFC SCLs of grades 1-3 were observed in 242 (9.65%) yearlings and 49 (11.2%) 2-year-olds. Bilateral MFC SCLs of grades 1-3 were observed in 54 (2.2%) yearlings and 12 (2.8%) 2-year-olds. Grade 1 MFC SCLs in yearlings either remained unchanged (14/31), progressed to a grade 2 (6/31) or resolved (11/31) by the 2-year-old sale. Grade 2 MFC SCLs in yearlings remained unchanged (6/10), progressed to a grade 3 (2/10) or improved to a grade 1 (2/10). Yearlings with a grade 3 MFC SCL had a 78% probability of starting a race (95% confidence interval [CI] 58.2-89.6%), compared with an 84% probability of racing for grade 0 yearlings (95% CI 82.7-85.8%). Six of the seven yearlings with axial MFC lucencies raced., Main Limitations: This study may underestimate the prevalence of severe lesions in the general yearling population of U.S. Thoroughbreds. However, the convenience sample used is representative of the population of interest at sales. The study design could not address exclusions prior to sale., Conclusions: Grade 1 MFC SCLs are the most common type seen in yearling and 2-year-old sales horses. The majority of yearling grade 1 MFC SCLs resolved or remained static by 2-year-old sales. It was also possible for grade 2 and 3 MFC SCLs to improve one grade between sales. Fewer sales yearlings with a grade 3 MFC SCL raced, but in those that did race there was no evidence of worse performance compared to unaffected peers. Axial MFC lucencies did not affect racing performance., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Intestinal epithelial stem cells (ISC) are responsible for epithelial regeneration and are critical to the intestine's ability to regain barrier function following injury. Evaluating ISC biomarker expression in cases of small intestinal strangulation (SIS) may provide insight into clinical progression., Objectives: Intestinal resection margins from cases of SIS were evaluated to determine if (1) evidence of injury could be identified using histomorphometry, (2) ISC biomarker expression was decreased in the proximal resection margin compared to control and distal resection margin, and (3) the ISC biomarker expression was associated with the number of preoperative risk factors negatively related to outcome, post-operative complications, or case outcome., Study Design: Retrospective cohort study., Methods: Intestinal samples were obtained intraoperatively from resection margins of adult horses with SIS and horses euthanised for reasons unrelated to colic. Preoperative risk factors negatively related to outcome, post-operative complications, and case outcome were obtained from medical records. Horses were grouped as euthanised intraoperatively, postoperatively, or survived to discharge. Histomorphometry and immunofluorescence were performed to evaluate tissue architecture and ISC and progenitor cell number. Groups were compared using one-way ANOVA. Associations between biomarker expression and the number of preoperative risk factors and post-operative complications negatively related to outcome were determined using linear regression modelling., Results: Thirty-six cases of SIS were evaluated. Ki67 + cell counts were decreased in the proximal (mean = 15.45 cells; 95% CI = 10.27-20.63; SD = 4.17; p = 0.02) and distal resection margins (mean = 15.05; 95% CI = 8.46-21.64; SD = 4.141; p = 0.03) in horses euthanised postoperatively compared to control (mean = 23.62 cells; 95% CI = 19.42-27.83; SD = 5.883). In the distal resection margin, an increase in SOX9 + Ki67 + cells were associated with a decrease in the total number of preoperative risk factors negatively related to outcome (95% CI = 0.236-1.123; p = 0.008, SE = 0.1393)., Main Limitations: Small population size., Conclusions: Proliferating cell and ISC numbers may be associated with case outcome., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Low-field magnetic resonance imaging (MRI) is widely available to equine veterinarians yet is insensitive at detecting cartilage damage in the distal interphalangeal joint (DIPJ). T2 mapping is a quantitative imaging technique that can detect cartilage damage before morphological change is apparent., Objectives: Validation of a T2 mapping sequence on a low-field MR system. Correlation of the mean T2 relaxation time in sections of cartilage with varying levels of pathology using low- and high-field MRI., Study Design: Cross-sectional study., Methods: Eight phantoms with known (nominal) T2 values underwent low-field (0.27 T) MRI and 38 ex vivo DIPJs were imaged. A further 9 ex vivo DIPJs were imaged on both the low- and high-field MR systems. Immediately after imaging, the DIPJs were disarticulated and samples collected for histology. Histological sections were graded using the Osteoarthritis Research Society International (OARSI) scoring system. Fiji ImageJ software with the MRIAnalysisPak plugin was used to calculate T2 maps and draw the regions of interest (ROIs)., Results: There was close agreement between the nominal and the measured T2 values in the phantom study. Spearman's rank correlation demonstrated significant positive correlation between low- and high-field T2 measurements, rho 0.644 (p < 0.001). The intrarater agreement for T2 measurements was excellent, intraclass correlation coefficient (ICC) = 0.99 (95% confidence interval [CI] = 0.99-1.00), the inter-rater agreement was excellent, ICC = 0.88 (95% CI = 0.82-0.92) and there was good intrarater agreement for OARSI scores (к = 0.76)., Main Limitations: Only a small number of histological samples were analysed. Both articular cartilage surfaces were measured within the ROI. There were no OARSI grade 0 control samples., Conclusions: A T2 mapping sequence on a low-field 0.27 T MR system was validated. There was a positive correlation between low- and high-field T2 measurements. The findings suggest a higher mean T2 relaxation time in pathological cartilage tissue examined in this study compared to normal equine cartilage tissue., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: The health and performance of horses are significantly affected by diseases associated with the hoof. Laminitis is a critical hoof disease that causes pain and, potentially, severe hoof and bone pathology., Objective: To generate an equine hoof finite element (FE) model to investigate the impact of normal and toe-in hoof conformations on the degeneration (decrease in elastic modulus) of the laminar junction (LJ), as occurs in chronic laminitis., Study Design: Computer software modelling., Methods: A hoof FE model was generated to investigate the biomechanics of hoof laminitis. A 3D model, consisting of nine components, was constructed from computed tomography scans of an equine left forelimb hoof. The model was loaded with 100 cycles of trotting. Two different centres of pressure (COP) paths representing normal and toe-in conformations were assigned to the model. LJ injury was modelled by degenerating the tissue's elastic modulus in the presence of excessive maximum principal stresses., Results: FE models successfully showed findings similar to clinical observations, confirming third phalanx (P3) dorsal rotation, a symmetric distal displacement of the P3 (2 mm at the lateral and medial sides) in the normal model, and an asymmetric distal displacement of the P3 (4 mm at the lateral and 1.5 mm at the medial side) in the toe-in model. The proximal distance between P3 and the ground after LJ degeneration in the current model was significantly different from experimental measurements from healthy hooves (P < 0.01)., Main Limitations: The inability to account for variations in population geometry and approximation of boundary conditions and system relations were the limitations of the current study., Conclusions: The distribution of LJ tissue degeneration was symmetric at the quarters in the normal hoof and in comparison, there was a lateral concentration of degeneration in the toe-in model., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Both type 1 (PSSM1) and type 2 polysaccharide storage myopathy (PSSM2) are characterised by aggregates of abnormal polysaccharide in skeletal muscle. Whereas the genetic basis for PSSM1 is known (R309H GYS1), the cause of PSSM2 in Quarter Horses (PSSM2-QH) is unknown and glycogen concentrations not defined., Objectives: To characterise the histopathological and biochemical features of PSSM2-QH and determine if an associated monogenic variant exists in genes known to cause glycogenosis., Study Design: Retrospective case control., Methods: Sixty-four PSSM2-QH, 30 PSSM1-QH and 185 control-QH were identified from a biopsy repository and clinical data, histopathology scores (0-3), glycogen concentrations and selected glycolytic enzyme activities compared. Coding sequences of 12 genes associated with muscle glycogenoses were identified from whole genome sequences and compared between seven PSSM2-QH and five control-QH., Results: Exertional rhabdomyolysis in PSSM2-QH occurred predominantly in barrel racing and working cow/roping performance types and improved with regular exercise and a low starch/fat-supplemented diet. Histopathological scores, including the amount of amylase-resistant polysaccharide (PSSM2-QH 1.4 ± 0.6, PSSM1-QH 2.1 ± 0.3, control-QH 0 ± 0, p < 0.001), and glycogen concentrations (PSSM2-QH 129 ± 62, PSSM1-QH 175 ± 9, control-QH 80 ± 27 mmol/kg, p < 0.0001) were intermediate in PSSM2-QH with significant differences among groups. In PSSM2-QH, abnormal polysaccharide had a less filamentous ultrastructure than PSSM1-QH and phosphorylase and phosphofructokinase activities were normal. Seventeen of 30 PSSM2-QH with available pedigrees descended from one of three stallions within four generations. Of the 29 predicted high or moderate impact genetic variants identified in candidate genes, none were present in only PSSM2-QH and absent in control-QH., Main Limitations: Analyses of PSSM2-QH and PSSM1-QH were performed on shipped samples, controls on frozen samples., Conclusions: PSSM2-QH is a novel glycogen storage disorder that is not the result of a mutation in genes currently known to cause muscle glycogenoses in other species., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Postoperative complications frequently occur following equine colic surgery but there is a lack of consistency in their definitions and reporting., Objectives: To perform a scoping review to identify current evidence on the definitions and classifications of postoperative complications in equine colic surgery., Study Design: Evidence review., Methods: A scoping review was conducted in CAB, Web of Science, Scopus and PubMed databases using a PCC (Population-equids, Concept-complications, adverse events, sequelae, failure to cure, technical failure, disease progression and Context-postoperative period after colic surgery) search strategy. Peer-reviewed scientific articles in the English language on equine colic surgery in live client-owned equids between 1992 and 2022 were included. The resulting references were independently and blindly screened by two investigators. Relevant data on the study method, sample size, intestinal tract involvement and postoperative complications were extracted and charted., Results: Among 5850 articles potentially eligible, 272 met the final inclusion criteria. The most frequent types of study design were retrospective cohort studies (121/272) and retrospective case series (82/272). Median sample size was 53 animals, range 3-896. Seventy-nine of 272 (29%) studies reported diseases of the small intestine, 65 of 272 (24%) of the large intestine and 128 of 272 (47%) reported both. Seventy-two studies (26.4%) focused on single complications. No study explicitly defined the term complication or cited a classification of complications. One study reported the definitions of 'sequela', 'progression' or 'recurrence' of lesions. Eighty-one postoperative complications were reported in two-time frames defined as short- and long-term. The definitions of most complications and long-term follow-ups were highly variable., Main Limitation: Non-English language studies or conference proceedings were excluded., Conclusion: There was a substantial lack of classifications of postoperative complications. The definitions of complications were highly variable, making it difficult to compare studies. Adopting classification systems and definitions may help surgeons to obtain a complete picture of the efficacy of a procedure or treatment and allow comparisons between studies, centres or time periods., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Osteoarthritis (OA) is a major cause of equine lameness. Cannabinoid (CB) receptors are now considered to be promising therapeutic targets in human rheumatology for pain and inflammation, however, little is known about the equine endocannabinoid system., Objectives: The primary goal was to assess the presence and expression pattern of CB1 and CB2 in the synovium of healthy joints. A secondary goal was to explore the relationship between the CB expression, degree of synovitis and OA pathology., Study Design: Ex vivo experimental study., Methods: Metacarpophalangeal joints (n = 25) from a tissue bank were studied. The joints were dissected, and the articular cartilage lesions were scored. Synovial membrane specimens (n = 45) were harvested, fixed and the degree of synovitis was graded on histological sections. Colocalised synovial sections were also immunostained with antibodies to CB1 and CB2. Five regions of interest were randomly selected from digital images of manually segmented synovial intima and scored blindly for positive cellular immunoreactive staining by two independent observers. Interobserver agreement was calculated with an intraclass correlation coefficient (ICC). Relationships between CB1 and CB2 immunoreactive scores and synovitis or joint OA grade were explored with mixed linear models., Results: CB1 was expressed in synovial intimal cells in all specimens studied whereas CB2 expression was identified in 94%. Both receptors were also expressed in the subintimal blood vessel walls. ICCs were 84.6% (CB1) and 92.9% (CB2) for the immunoreactivity scores. Both CB1 and CB2 expression were significantly upregulated (p = 0.04 and p = 0.03, respectively) with increasing degree of synovitis. Conversely, CB1 expression significantly decreased (p = 0.03) with increasing severity of OA., Main Limitations: The type of synovial cell expressing CB1 or CB2 was not investigated., Conclusion: Equine synovial intimal cells constitutively express both CB1 and CB2 receptors that are upregulated with synovitis and may have a role in joint pain. They are potential targets for therapy with cannabinoid molecules or their derivatives., (© 2022 EVJ Ltd.)

Background: Surgical stabilisation of the distal phalanx (DP) is a potential therapeutic strategy for severe acute laminitis., Objective: To evaluate the effects of locking compression plate (LCP) fixation of the DP to the dorsal hoof wall., Study Design: Ex vivo and in vivo experiments., Methods: A T-shaped LCP was applied to one limb per pair in six pairs of cadaver forelimbs subjected to a combination of thermally induced lamellar failure and vertical load to simulate severe acute laminitis. Standard radiographic measurements were used to compare DP displacement. The LCP was then applied to one forefoot in 12 healthy Standardbred horses either standing (n = 6) or under general anaesthesia (n = 6). Lameness was evaluated daily, then horses were euthanised (day 8) and lamellar tissue analysed using light microscopy, histomorphometery and molecular markers of apoptosis., Results: In the cadaver limb model, LCP fixation prevented the significant changes in hoof-distal phalanx distance, coronary extensor process distance and sole depth that characterised DP displacement in untreated limbs (p < 0.05). Application of the construct in vivo was well tolerated with minimal lameness (10/12 horses were sound at the trot on day 8); however, histology revealed dorsal lamellar pathology consistent with laminitis, but with extensive keratinocyte apoptosis. Adjacent to the LCP, caspase-3 positive cell counts were approximately 20-fold higher than control (p < 0.001)., Main Limitations: Pathology was evaluated at a single time point. Microvascular perfusion was not evaluated., Conclusions: Rigid fixation of the DP to the hoof capsule was achieved with the LCP construct in a cadaver limb laminitis model. In live horses, LCP fixation caused regional lamellar pathology with extensive apoptosis, likely due to disturbed lamellar microvascular perfusion and/or mechanostasis. Understanding these mechanisms is critical for refinement of the technique in order to avoid iatrogenic lamellar damage., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Equine laminitis has both fascinated and frustrated veterinary researchers and clinicians for many years. The recognition that many ponies suffering from pasture-associated laminitis have an insulin-dysregulated phenotype (endocrinopathic laminitis, EL) and that prolonged insulin and glucose infusions can experimentally induce laminar pathology and functional failure are seminal discoveries in this field. Researchers have studied the molecular basis for disease pathogenesis in models of EL, sepsis-related laminitis and supporting limb laminitis and generated much data over the last 15 years. This review attempts to synthesise those data, drawing comparisons between models and naturally occurring laminitis. A hypothesis is proposed that the basal epithelial cell stress is a central event in each category of laminitis. Furthermore, in naturally occurring pasture-associated laminitis, pathways that predominate in each type of laminitis contribute to laminar lamellar pathology to varying extents. Based on the molecular mechanisms determined in experimental models, interactions between these pathways are identified., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is a destructive, painful and underdiagnosed dental disorder. Radiography is necessary to fully assess the disease as early stages occur on clinically normal teeth., Objectives: To investigate the distribution pattern of appearance of EOTRH within the incisor arcade. In particular, we aimed to determine the influence of tooth position and horse age on the severity of EOTRH as well as on the frequency of the individual severity stages., Study Design: Retrospective cross-sectional radiographic case study., Methods: Digital radiographs of 142 horses (10 years and older) presented for routine dental examination at our Equine Hospital were obtained and evaluated for changes related to EOTRH. Radiological findings were classified in terms of EOTRH severity, and each tooth was evaluated individually (tooth stage)., Results: The tooth stages of EOTRH showed a bilateral symmetrical distribution pattern over the entire incisor arcade. There was a significant positive correlation between age and tooth stages (p < 0.001, rho = 0.48, 95% CI 0.43-0.51), and the frequency of higher tooth stages increased from central incisors to middle and corner incisors., Main Limitations: Individual head anatomy in some male horses lead to superimposition of the lower jaw corner incisors and canine teeth. The radiographic technique proved difficult in smaller and uncooperative horses. Differentiating between mild pathological signs of EOTRH and age-related radiological changes was not possible in all cases., Conclusion: These results reconfirm an age-correlated progression of EOTRH. EOTRH affects the incisor arcade in a bilaterally symmetrical pattern with the corner incisors being the most severely affected., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Genetic tests for variants in MYOT (P2; rs1138656462), FLNC (P3a; rs1139799323 or P3b; rs1142918816) and MYOZ3 (P4; rs1142544043) genes are offered commercially to diagnose myofibrillar myopathy (MFM) and type 2 polysaccharide storage myopathy (PSSM2) in Quarter Horses (QH)., Objectives: To determine if PSSM2-QH has histopathological features of MFM. To compare genotype and allele frequencies of variants P2, P3, P4 between control-QH and PSSM2-QH diagnosed by histopathology., Study Design: Retrospective cross-sectional., Methods: The study includes a total of 229 healthy control-QH, 163 PSSM2-QH GYS1 mutation negative. Desmin stains of gluteal/semimembranosus muscle were evaluated. Purported disease alleles P2, P3a, P3b, P4 were genotyped by pyrosequencing. Genotype, allele frequency and total number of variant alleles or loci were compared between phenotypes using additive/genotypic and dominant models and quantitative effects evaluated by multivariable logistic regression., Results: Histopathological features of MFM were absent in all QH. A P variant allele at any locus was not associated (P > .05) with a histopathological diagnosis of PSSM2 and one or more P variants were common in control-QH (57%) and PSSM2-QH (61%). Allele frequencies (control/PSSM2) were: 0.24/0.21 (P2), 0.07/0.12 (P3a), 0.07/0.11 (P3b) and 0.06/0.08 (P4). P3a and P3b loci were not independent (r 2  = 0.894); and not associated with PSSM2 histopathology comparing the haplotype of both P3a and P3b variants to other haplotypes. A receiver operator curve did not accurately predict the PSSM2 phenotype (AUC = 0.67, 95% CI 0.62-0.72), and there was no difference in the total number of variant loci or total variant allele count between control-QH and PSSM2-QH., Main Limitations: P3a and P3b were not in complete linkage disequilibrium., Conclusions: The P2, P3 and P4 variants in genes associated with human MFM were not associated with PSSM2 in 392 QH. Their use would improperly diagnose PSSM2/MFM in 57% of healthy QH and fail to diagnose PSSM2 in 40% of QH with histopathological evidence of PSSM2., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: In clinical practice, early diagnosis of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) and other resorptive incisor diseases is difficult to achieve. The radiographic appearance of subtle pathological changes has not been described in detail and might be confused with age-related changes., Objectives: The study was performed to define typical radiographic signs of early incisor lesions and to evaluate the reliability of the radiographic findings., Study Design: Descriptive and comparative study using post mortem clinical, radiographic, macroscopic and µCT examination., Methods: The incisor region of 20 cadaveric horse heads, divided into three different age groups, was examined visually and by palpation. Intraoral radiographs were taken. After extraction, each incisor was macroscopically evaluated. Micro-computed tomography (µCT) scans were obtained. These scans were processed with Scry (v6.0, Kuchel & Sautter GbR) to obtain surface meshes which then were transferred to Meshlab (ISTI-CNR, version 2016.12). Attached tissues were virtually removed and surface curvature was computed to visualise and evaluate the quantity of unevenness (roughness) of the teeth's surface. Scoring systems for each diagnostic modality were developed. Scores were compared to describe and evaluate the radiographic appearance of early incisor lesions., Results: The prevalence and severity of incisor lesions increased with age. Early, subtle lesions develop on the palatal/lingual side of incisors. While radiographically detected lesions were confirmed macroscopically and on the µCT scans, numerous teeth which were radiographically classified as healthy displayed lesions by macroscopic inspection (13.7%) and µCT analysis (58.1%)., Main Limitations: Cadavers were studied and dental history was unknown., Conclusions: The detection of early and subtle incisor lesions indicating first signs of EOTRH on dorsoventral intraoral radiographs is limited due to the typical localisation of the lesions on the palatal/lingual side of the incisors., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Plantar osteochondral fragments (POF) are common but their effect on joint health of young Standardbreds in race training is largely unknown., Objectives: Evaluate the inflammatory effects of POF in metatarsophalangeal joints of young Standardbreds as a step towards developing evidence-based recommendations for surgical removal., Study Design: Cohort study., Methods: Forty-nine Standardbred horses (age 11-33 months) presented for surgical removal of POF from 56 metatarsophalangeal joints. Synovial tissue collected at arthroscopy was subjected to histopathology. IL-1β, TNF-α, and PGE-2 were measured in synovial fluid using ELISA. Digital arthroscopy images were scored for inflammation. Racing performance data were retrieved from a public database., Results: Median time in race training prior to surgery was 8 weeks (IQR 4-12; range 0-40). There was minimal evidence of synovial inflammation as assessed by histopathology (median total score 2/20, IQR 0-2, range 0-5) or arthroscopy (median average total score 2.67/15, IQR 1.79-4, range 0-8.83). IL-1β was not detected in any sample. TNF-α (median 0 pg/mL, IQR 0-0) and PGE-2 (median 56.6 pg/mL, IRQ 40.5-99.8) were measured at low levels. Weeks in training prior to surgery was associated with the number of starts in the season after surgery (incidence rate ratio 1.02, 95% CI 1.00, 1.04, P = .03)., Main Limitations: Small sample size from a single breed with a relatively short training time prior to surgery., Conclusions: There was minimal evidence of synovial inflammation in the metatarsophalangeal joints in this population of young Standardbred horses with POF. It is possible that POF may result in a different inflammatory response than other fragments because they are generally well-embedded in situ. These findings suggest that, in Standardbreds, race training can commence several weeks prior to surgical removal of POF with minimal detrimental effects on joint health, although further investigation of long-term effects of POF on joint health is warranted., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Digital flexor tendon sheath (DFTS) pathology is an important cause of lameness in horses. The outcome after surgical treatment is variable and depends on the exact diagnosis., Objectives: To (1) describe the prevalence of lesions associated with lameness caused by nonseptic DFTS tenosynovitis in a large population of German sports and pleasure horses; (2) determine the sensitivity and specificity of diagnostic imaging techniques for identifying lesions within the DFTS with tenoscopic diagnosis being the gold standard; (3) explore associations between tenoscopically diagnosed lesions and signalment, purpose, and limb affected; and (4) describe the outcome following DFTS tenoscopy with nonseptic DFTS tenosynovitis in this population., Study Design: Retrospective case series., Methods: Medical records of horses admitted for tenoscopic surgery of nonseptic DFTS tenosynovitis between 2011 and 2020 were reviewed. Follow-up information was obtained via telephone contact. Sensitivity and specificity of ultrasonography and contrast tenography were determined using tenoscopic diagnosis as gold standard and univariable analysis was used to explore associations between signalment, case history, and tenoscopic diagnosis., Results: Medical records from 131 horses were retrieved, of which 8 horses had bilateral disease and 6 horses were presented for tenoscopy on two separate occasions (3 for tenoscopy in the same limb, 3 in a different limb), thus, making a total of 145 limbs. Lesions were most commonly diagnosed in the deep (DDFT; n = 55 limbs) and superficial (SDFT; n = 55 limbs) digital flexor tendons. Manica flexoria (MF) lesions were detected in 44 limbs and palmar/plantar annular ligament (PAL) constriction in 99 limbs. In 36 limbs, only one structure within the DFTS was injured, whereas in 109 limbs a combination of lesions was noted, the most common being the combination of a SDFT lesion with PAL constriction. All affected limbs were examined with diagnostic ultrasonography; contrast tenography was performed in 86 limbs. For diagnosis of MF and DDFT tears, tenography was more sensitive (89% [confidence interval, CI: 65.4%-95.2%]; 72% [CI: 46.4%-89.3%], respectively) than specific (64% [CI: 52.5%-77.6%]; 53% [CI: 42.2%-73.3%], respectively) whereas ultrasonography was more specific (92% [CI: 84.5%-96.3%]; 92% [CI: 83.6%-96.0%]) with lower sensitivity (64% [CI: 47.7%-77.2%]; 54% [CI: 39.5%-67.9%]). For SDFT lesions, ultrasonography was highly specific (94% [CI: 86.9%-97.9%]) with lower sensitivity (66% [CI: 51.3%-77.4%]). Follow-up information following first surgery was obtained for 118 horses (132 limbs): 18 (15.3%) of 118 horses remained chronically lame, 40 (33.8%) performed at a reduced level and 60 (50.8%) performed at the same or higher level following rehabilitation after tenoscopy. Horses with DDFT lesions had the poorest outcomes with only 36.6% returning to the same or higher level of exercise., Main Limitations: Retrospective analysis of clinical records and subjective outcome assessment based on owner follow-up with potential recall bias. Findings on diagnostic imaging are impacted by many factors including equipment quality and operator expertise and experience., Conclusion: Diagnostic imaging techniques were complimentary and contrast tenography was sensitive and ultrasonography was specific for the diagnosis of MF and DDFT lesions. Following tenoscopic surgery for nonseptic tenosynovitis of the DFTS, approximately half the cases were able to return to preinjury level of exercise., (© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Comparison of radiography to magnetic resonance imaging (MRI) can help objectively assess the value and limitations of radiographs in orthopaedic disease processes. The tarsus and proximal suspensory origin of the metatarsus are commonly imaged regions for lameness. The knowledge gained by comparison between imaging modalities will aid in improving accuracy of radiographic interpretation., Objective: To compare the radiographic and MRI findings of the proximal third metatarsal bone (MTIII) and proximal suspensory ligament using MRI as the gold standard., Study Design: Retrospective observational study., Methods: Single hindlimbs of 35 horses with radiographic and high-field (3Tesla (3T)) MRI studies were blindly evaluated by two board-certified veterinary radiologists and a radiology resident. Severity and location of the following parameters were assessed: radiographic MTIII sclerosis and lucent regions, MRI endosteal metatarsal sclerosis and bone marrow lesions, plantar cortical proliferation and resorption, and proximal suspensory desmopathy (PSD)., Results: Radiographic osseous changes of MTIII were identified in 54% of limbs, whereas 40% limbs had osseous changes on MRI: 43% of limbs had PSD on MRI. No significant association was found between the presence of radiographic changes in MTIII and PSD on MRI (P = .7). A statistically significant association and positive correlation was found between the severity of radiographic changes and MTIII plantar cortical proliferation and resorption on MRI (P = .01)., Main Limitations: Retrospective study with no histopathology. Ability to correlate findings with lameness was limited by the lack of standardised time intervals between onset of lameness, diagnostic analgesia and advanced imaging., Conclusion: Radiographic bony changes of proximal MTIII do not reliably predict presence or severity of PSD but are associated with osseous changes at the proximal MTIII. The presence of radiographic changes should warrant additional diagnostics in the region prior to making conclusions about the presence or absence of PSD., (© 2022 EVJ Ltd.)

Background: High-power laser therapy gained popularity recently as a regenerative treatment for tendinitis and desmitis in the horse. However, studies evaluating the effects of laser therapy on tissue repair at the histological level in large mammals are lacking., Objectives: To evaluate the effects of high-power laser therapy on suspensory desmitis healing, using a model of suspensory ligament branch injury., Study Design: In vivo experiments., Methods: Standardised lesions were surgically induced in all four lateral suspensory branches of 12 healthy Warmblood horses. Laser therapy (class 4, 15W) was applied daily on two of four induced lesions for four consecutive weeks. Horses were randomly assigned to either short-term study (horses were sacrificed after 4 weeks) or long-term study (6 months). Suspensory ligament samples were scored after staining with haematoxylin-eosin and immunostaining for collagen 1- collagen 3- and factor VIII., Results: In the short-term study, significantly better (lower) scores for variation in density (17% above cut-off score in treated lesions vs. 31% above cut-off score in controls, P = .03), shape of nuclei (54% vs 92%, P = .02), fibre alignment (32% vs 75%, P = .003) and fibre structure (38% vs 71%, P = .02) were found in laser-treated lesions when compared to controls. Collagen 3 expression was significantly higher (32% vs 19%, P = .006) in control lesions. In both short- and long-term studies combined, parameters lesion size (44% vs 56%, P = .02) and shape of nuclei (53% vs 84%, P = .05) scored significantly better in treated lesions. Long-term, significantly better (lower) scores were found in the laser-treated group for lesion size (15% vs 45%, P = .008) and a higher percentage above cut-off score for density of the nuclei (27% vs 9%, P = .02), compared to controls., Main Limitations: The model of suspensory branch injury is not an exact representation of clinical overstrain lesions., Conclusions: These results suggest that high-power laser therapy enables better lesion healing than conservative treatment., (© 2022 EVJ Ltd.)

Background: The iridocorneal angle (ICA) is the major pathway of aqueous humour outflow from the anterior chamber of the eye. Ultrasound biomicroscopy (UBM) has been utilised to characterise the morphology of this drainage pathway in numerous species. UBM may allow for early recognition of aqueous humour outflow obstructions in horses, allowing for earlier recognition of risk for glaucoma, a vision-threatening and painful disease. UBM morphology of the normal equine ICA has yet to be described., Objectives: To determine the ultrasonographic morphology of the equine ICA by UBM in standing sedated horses., Study Design: In vivo experimental study., Methods: Thirty healthy adult horses underwent UBM of the ICA at four locations (superior, temporal, inferior, nasal) of each eye utilising standing sedation, topical anaesthesia and auriculopalpebral perineural anaesthesia. Anatomic structures were defined on ultrasound images through comparison to published histologic photomicrographs of the equine ICA., Results: Ultrasound imaging of the ICA at all four locations was easily performed in standing, sedated horses. High-resolution images of the ICA allowed for identification of the pectinate ligament, corneoscleral trabecular meshwork (TM), uveal TM and supraciliary TM., Main Limitations: Pupil size was midrange in all eyes, but was not strictly controlled. Lighting conditions not controlled. Various breeds included., Conclusion: In vivo UBM of the equine ICA is feasible and provides high-resolution images of the structures of the aqueous humour outflow pathway., (© 2022 EVJ Ltd.)

Background: Airway smooth muscle remodelling in severe equine asthma includes both thickening of airway smooth muscle, resulting from hyperplasia and hypertrophy, and changes in contractility. However, airway smooth muscle changes have not been studied in milder forms of the disease., Objectives: To investigate bronchial smooth muscle remodelling in horses with mild and moderate asthma (MEA)., Study Design: Retrospective case-control study., Methods: The endobronchial biopsies from 18 horses with MEA referred to the Equine Hospital of the Université de Montréal and from seven healthy age-matched control horses were studied. The diagnosis was based on clinical signs and bronchoalveolar lavage fluid cytology. Airway smooth muscle cell proliferation was measured by quantifying the expression of the proliferating cell nuclear antigen (PCNA) using immunohistochemistry and histomorphometry. The expression of the (+)insert smooth muscle myosin heavy chain (SMMHC) isoform, an hypercontractile protein, was assessed by RT-qPCR., Results: Expression of the (+)insert SMMHC isoform in airway smooth muscle was approximately 1.5 times greater in horses with MEA compared with controls (P = .02, mean difference 0.01). Although there were no differences between groups in the proliferation of airway smooth muscle cells (P = .4) or myocyte density (P = .3, mean difference -0.6), the percentage of proliferating myocytes was correlated to pulmonary neutrophilia in horses with neutrophilic inflammation (P = .01, r = .80) and to the expression of the (+)insert SMMHC isoform in asthmatic horses (P = .03, r = .66)., Main Limitations: Small cohorts of horses were studied, and conclusions are limited to the central airways., Conclusions: These results confirm the presence of bronchial smooth muscle remodelling in mild forms of equine asthma and pave the way for the development of biomarkers to measure asthma progression and response to therapy., (© 2021 EVJ Ltd.)

Background: There is a knowledge gap about how equine MFC subchondral radiolucencies (SR) arise and evolve. Osteoclasts are believed to have a role but have not been studied in situ., Objectives: To measure and compare osteoclast density and the percentage of chondroclasts in healthy and MFC SR specimens from juvenile Thoroughbreds., Study Design: Cadaveric study., Methods: Medial femoral condyles (MFC) from a tissue bank of equine stifles were studied. Inclusion criteria were MFCs (≤8 months old) with a computed tomography SR lesion and histological focal failure of endochondral ossification (L group). Contralateral, lesion-free, MFCs were a control group (CC). Osteochondral slabs were cut through the lesion (L), a healthy site immediately caudal to the lesion, (internal control; IC) and the contralateral, site-matched controls (CC). Histological sections were immunostained with Cathepsin K for osteoclast counting. Osteoclasts in contact with the growth cartilage (chondroclasts) were also counted. The sections were segmented into regions of interest (ROI) at different depths in the subchondral bone: ROI 1 (0-1 mm), ROI 2 (1-3 mm) and ROI 3 (3-6 mm). Osteoclasts were counted and the bone area was measured in each ROI to calculate their density. Chondroclasts were counted in ROI 1 ., Results: Sections were studied from L and IC (n = 6) and CC sites (n = 5). Osteoclast density was significantly higher in ROI 1 when compared with ROI 3 in all groups. Although higher osteoclast density was measured in ROI 1 in the L group, no significant differences were detected when compared with control ROIs. The proportion of chondroclasts in ROI 1 was lower in the L sections when compared with controls but no significant differences were detected., Main Limitations: Limited sample size., Conclusions: Osteoclasts are important actors in MFC subchondral bone development, digesting both growth cartilage (chondroclasts) and bone, but the pathophysiology of early MFC SRs cannot be explained solely by an increased osteoclast presence in the subchondral bone., (© 2021 EVJ Ltd.)

Background: Correct diagnosis and characterisation of deep digital flexor tendon (DDFT) lesions in equine athletes allows targeted treatment and improved prognostication., Objectives: To assess the prevalence and character of pathological change within the DDFT in the pastern with concurrent tendon injury distally. It is hypothesised that tendon lesions in the pastern will be associated with tendinopathy within the hoof capsule., Study Design: Retrospective descriptive case series., Methods: Cases with DDFT lesions in the pastern and magnetic resonance imaging (MRI) or ultrasonography of the foot were evaluated retrospectively. Lesion location and type were recorded. Odds ratios were calculated to determine the associations between more distal tendinopathy and the presence of different DDFT lesion types in the pastern., Results: Thirty-four MRI scans of 33 horses and 64 ultrasonographic exams of 58 horses were analysed. Lesion location and type were recorded. Distal DDFT lesions were found in 75% (95% CI: 66.0-84.0) of total cases of pastern DDF tendinopathy and in 97% (95% CI: 91.6-100.0) of cases with core lesions of the DDFT in the pastern. A core lesion in the pastern was significantly more likely (OR = 20.7, 95% CI: 2.2-191.0; P = .008) to be associated with injury in the foot than other types of pastern lesion., Main Limitations: MRIs of the foot were not obtained on all included limbs which did not allow for fully inclusive evaluation of DDFT lesions distal to the navicular bone., Conclusions: DDFT pathological change in the pastern, particularly core lesions, is associated with additional tendinopathy within the hoof capsule. When a DDFT lesion is found in the pastern, further imaging of the tendon within the foot is indicated to direct appropriate treatment and improve prognostication., (© 2021 EVJ Ltd.)

Background: Sagittal fractures of equine cheek teeth are commonly observed during oral examination. There are few reports on the apical and endodontic pathology associated with such fractures seen during computed tomographic (CT) examination., Objectives: This study aimed to document the prevalence of CT changes indicative of apical disease in equine cheek teeth, which have suffered a sagittal fracture involving the clinical ± reserve crown., Study Design: This study is a retrospective case series., Methods: CT examinations of equine heads with sagittal fractures of cheek teeth present were reviewed: 81 teeth from 49 horses were identified to have a sagittal cheek tooth fracture. The images were evaluated for apical pathology including gas (in the endodontic system and periapically), widened periodontal space, periapical sclerosis, apical clubbing, cementoma/hypercementosis, lamina dura loss, associated sinusitis and sinus mucosal swelling. An apical infection grading system was created to give each tooth a score. Hounsfield units were used to measure the density of the endodontic, apical and periapical regions. The fracture length ratio was recorded. Statistical analysis was performed using a generalised estimating equation to evaluate predictors of apical infection and associations between clinical signs and CT abnormalities., Results: Eighty-seven sagittal fractures (56 buccal, 17 palatal/lingual and 14 midline) from 81 teeth were recorded (74 maxillary and 7 mandibular). Apical infection was diagnosed in 73% (37/51, P = .05) of buccal, 55% (6/11, P = .07) of palatal/lingual, 100% (13/13) of midline, 100% (6/6) of multiple fractures and 96% (23/24, P = .008) of fractures involving infundibula. There was no significant relationship between apical infection and the presence of clinical signs associated with dental pathology (P = .4). There was no significant association between fracture length ratio and apical infection (P = 1.0). Midline sagittal fractures were significantly associated with sinusitis when compared with all other maxillary fractures (odds ratio [OR] 5.92, 95% confidence interval [CI] 1.67-20.83, P = .006). Loss of the lamina dura was not significantly associated with apical infection (P = .5)., Main Limitations: There is a maxillary cheek tooth bias in the data set and the subjective grading system., Conclusions: A large proportion of fractured cheek teeth have evidence of apical infection on CT examination and therefore warrant treatment., (© 2021 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: The aetiology of equine medial femoral condyle (MFC) subchondral bone radiolucencies (SR) is unknown., Objectives: Characterise the microstructural structural features of MFC SR in juvenile Thoroughbreds with microcomputed tomography (μCT) and histology., Study Design: Cross-sectional post-mortem study., Methods: Distal femurs were collected at post-mortem. Conventional tomodensitometry was employed to scout for MFCs with and without SR lesions (SR+ and SR-, respectively). Group 1 were CT MFC SR+ and Group 2 age-matched SR- controls. Both underwent μCT and histological analysis. Group 3 CT MFC SR- foals, <6 months, were selected to search for chondronecrosis. Histological sections, processed from the lesion (Group 1) and a corresponding site in Groups 2 and 3, were assessed for chondronecrosis, fibrin, fibroplasia and osteochondral separation. Group 3 sections were surveyed for chondronecrosis alone., Results: A total of 178 femurs from 89 Thoroughbreds were harvested. Of these horses 19.1% (95% CI: 10.9%-27.3%) were CT MFC SR+ (17/23; 7.46 ± 4.36 months) and met the inclusion criteria for Group 1. Group 2 included 30 CT MFC SR- specimens (5.00 ± 2.73 months) and Group 3 had 44 CT MFC SR- s (2.68 ± 1.74 months). SR were located axially in foals <7 months of age, and centrally thereafter. All SRs had areas of thickened cartilage on histology and separation at the osteochondral junction containing fibrin (acute event) and fibroplasia (chronicity) in 73.9% (17/23; 95% CI: 56%-91.9%). In Group 1 specimens, chondronecrosis was present in 82.6% (19/23; 95% CI: 67.1%-98.1%) but four MFC SR+ had no evidence of chondronecrosis. Chondronecrosis was not detected in the Group 3 foal MFCs., Main Limitations: No longitudinal follow-up., Conclusions: The absence of chondronecrosis, pathognomic of osteochondrosis, in four MFC SR+s and in all of the CT MFC SR- foals suggests that osteochondrosis is not the cause, or the only cause, of these lesions and favours trauma as an alternate aetiological hypothesis., (© 2021 EVJ Ltd.)

Background: Peripheral caries (PC) has recently been shown to affect over half of UK and Australian horses., Objectives: To examine affected cheek teeth histologically and ultrastructurally, to assess the possible route(s) of carious infection into the dental tissues and to further describe the pathological changes in affected teeth., Study Design: Descriptive pathological study., Methods: Four control and 16 cheek teeth with different grades of PC were examined grossly, histologically and by electron microscopy., Results: Cariogenic bacteria from plaque entered peripheral cementum perpendicular to the sides of teeth alongside Sharpey's fibres or vascular channels or more horizontally alongside exposed intrinsic fibres and cemental growth lines. Subsequent intra-cemental bacterial spread created different patterns of caries including vertical and horizontal flake-like patterns; deep, large flask-shaped or smaller superficial ellipsoid-shaped lytic lesions. Cemental caries progressed to affect enamel, dentine and even pulp. Gross examination underestimated the degree of caries observed on histological evaluation., Main Limitations: No dental histories were available; all teeth were examined on a single occasion., Conclusion: Equine PC causes different patterns of cemental lesions that appear dependent on the route of cariogenic bacterial invasion. Progression of caries can lead to pulpitis and tooth loss. Gross examination can underestimate the true extent of caries., (© 2019 EVJ Ltd.)

Background: Ulcerative keratitis with peripheral furrow formation is a poorly-described condition which has been associated with a grave prognosis due to rapid necrosis of the cornea., Objective: To describe the infectious aetiologies associated with furrow-forming ulcerative keratitis, its overall clinical course and the efficacy of medical and surgical intervention in horses., Study Design: Retrospective clinical case series., Methods: Medical records of 72 horses which presented with furrow-forming ulcerative keratitis at the University of Florida between 1987 and 2015 were reviewed., Results: Seventy-two horses (72 eyes) with furrow-forming ulcerative keratitis were treated at the University of Florida between 1987 and 2015. Of these, a definitive aetiologic diagnosis was available for 37 eyes. Ten of 37 eyes (27%) were diagnosed with fungal keratitis based on cytology of corneal scraping, culture, histopathology and/or fungal PCR. Fourteen of 37 eyes (38%) were diagnosed with a mixed fungal and bacterial keratitis. Thirteen of 37 eyes (35%) were diagnosed with bacterial keratitis. Overall, 26 of 72 total eyes were treated with medical therapy alone (36%). Forty-six of 72 eyes were treated medically and surgically (64%). Of the 26 eyes which received medical therapy, 20 healed with a positive visual outcome (77%) and 6 eyes were non-visual (23%). Of the 46 eyes which received surgical intervention, 40 healed with a positive visual outcome (87%), while six eyes were non-visual (13%). Altogether, 60 of 72 eyes healed with a positive visual outcome following medical or surgical treatment of furrow-forming ulcerative keratitis (83%). Twelve of 72 eyes failed treatment (17%), with six eyes requiring enucleation and six globes becoming phthisical after treatment., Main Limitations: Inconsistencies in available medical record data due to the large span of time (1987-2015) are inherent in this retrospective study, along with gradual evolution of corneal surgical techniques and medical therapies over the decades., Conclusions: Furrow-forming ulcerative keratitis was associated with a positive visual outcome in 83% of horses treated at the University of Florida between the years 1987 and 2015. Furrow formation may be associated with either fungal or bacterial infection., (© 2019 EVJ Ltd.)

Background: Strangulating small intestinal disease (SSID) carries a poor prognosis for survival in comparison to other types of colic, particularly if resection is required. Identification of markers which aid early diagnosis may prevent the need for resection, assist with more accurate prognostication and/or support the decision on whether surgical intervention is likely to be successful, would be of significant welfare benefit., Objectives: To apply an unbiased methodology to investigate the plasma and peritoneal fluid proteomes in horses diagnosed with SSID requiring resection, to identify novel biomarkers which may be of diagnostic or prognostic value., Study Design: Prospective clinical study., Methods: Plasma and peritoneal fluid from horses presented with acute abdominal signs consistent with SSID was collected at initial clinical examination. Samples from eight horses diagnosed with SSID at surgery in which resection of affected bowel was performed and four control horses subjected to euthanasia for orthopaedic conditions were submitted for liquid chromatography tandem mass spectrometry. Protein expression profiles were determined using label-free quantification. Data were analysed using analysis of variance to identify differentially expressed proteins between control and all SSID horses and SSID horses which survived to hospital discharge and those which did not. Significance was assumed at P≤0.05., Results: A greater number of proteins were identified in peritoneal fluid than plasma of both SSID cases and controls, with 123 peritoneal fluid and 13 plasma proteins significantly differentially expressed (DE) between cases and controls (P<0.05, ≥2 fold change). Twelve peritoneal fluid proteins (P<0.036) and four plasma proteins (P<0.05) were significantly DE between SSID horses which survived and those which did not., Main Limitations: A low number of samples were analysed, there was variation in duration and severity of SSID and only short-term outcome was considered., Conclusions: Changes in peritoneal fluid proteome may provide a sensitive indicator of small intestinal strangulation and provide biomarkers relevant to prognosis., (© 2019 EVJ Ltd.)

Background: Peripheral caries may cause significant oral pain and pathology and is very prevalent within the Western Australia horse population. Associations with periodontal disease have been indicated; however, further work is needed to assess the anatomical and histological aspects of the conditions, to better understand the pathophysiology., Objectives: To assess the anatomical and histopathological changes associated with equine cheek teeth peripheral caries and disease of the periodontium to better understand the pathogenesis and any association between the conditions., Study Design: Cross-sectional epidemiological and histological study., Methods: A survey of 500 Western Australia horses was performed to assess the prevalence of peripheral caries and associations with other dental pathologies within the Western Australia horse population. Histopathological assessment was also performed on four extracted cheek teeth affected by peripheral caries and on three interdental areas from an abattoir specimen affected by peripheral caries and interdental feed accumulation., Results: There was a significant association between peripheral caries and cheek teeth interdental feed accumulation and gingival recession. This association was significantly stronger in the mandibular cheek teeth than the maxillary cheek teeth and also in horses with moderate or severe peripheral caries compared to horses with mild peripheral caries. Histopathological examination found caries lesions consistent with those found in humans above the gingival margin. Sub-gingivally, however, the cementum and periodontal structures were normal. In the samples with concurrent peripheral caries and deep feed-pocketing, there was significant gingival recession; however, only mild or no histopathological changes occurred in the gingiva., Main Limitations: Small sample size for histopathological assessment., Conclusion: Horses with peripheral caries, and in particular, horses with mandibular cheek teeth with peripheral caries are significantly more likely to also be affected by disease of the periodontium than horses without peripheral caries., (© 2019 EVJ Ltd.)

Background: Equus caballus papillomavirus 8, a recently discovered virus, has been reported to cause generalised papillomavirus in horses., Objectives: To describe a case in which multiple viral plaques, viral papillomas, squamous cell carcinoma (SCC) in situ and invasive squamous cell carcinoma (ISCC) were associated with EcPV8 in a horse., Study Design: Case report., Methods: A 16-year-old mixed breed horse presented with dozens of raised crusted papular to nodular lesions over a course of 4 years. Masses had been surgically excised four times and cisplatin beads and emulsion were implanted on three different occasions; however new masses continue to develop in sites of previous masses as well as new sites., Results: Multiple viral plaques, viral papillomas, SCC in situ and ISCC, localised to the inguinal region, were diagnosed via histopathology. EcPV8 DNA was detected via PCR., Main Limitations: Since only a few cases have been reported, we do not know the incidence of EcPV8 nor how often it may be associated with SCC in situ or ISCC without further study., Conclusions: This is the fourth reported case of viral papillomatosis in the context of an EcPV8 infection in a horse. This is the first case in which SCC has been associated with EcPV8., (© 2018 EVJ Ltd.)

Background: Lameness can be multifactorial and may result from the accumulation of multiple seemingly unrelated causes. The identification of factors associated with lameness could be one method to decrease incidence of lameness and prolong the equine athlete's competitive life., Objectives: To determine if there is an association between hoof balance in the sagittal plane and hindlimb lameness., Study Design: Case-control study., Methods: Eighty client-owned horses with hindlimb lameness (cases) and 80 horses with no detectable hindlimb lameness (controls) were prospectively enroled following lameness evaluation as either cases (lameness localised with regional anaesthesia) or controls (no hindlimb lameness). Lameness cases were divided based on location (stifle, tarsus, proximal metatarsus and other sites). Lateromedial radiographs were performed on hind hooves and plantar angle of the distal phalanx (PADP) was determined. The prevalence of negative/neutral PADP and median PADPs were calculated. Conditional logistic regression and Wilcoxon signed rank tests were used to analyse PADPs, and odds ratios were calculated. Significance was set at P<0.05., Results: The mean PADP was significantly smaller in cases compared to controls. The mean PADP was significantly smaller in horses with lameness localised to tarsus and proximal suspensory, but not the stifle. Lameness in horses was associated with a negative/neutral PADP (Odds ratio [OR] 3.87, 95% confidence interval [95% CI] 1.97-7.61, P<0.01), with lameness localised to the tarsus (OR 4.98, 95% CI 1.34-18.54, P = 0.01) and proximal suspensory (OR 5.16, 95% CI 1.11-23.89, P = 0.03) being associated with a negative/neutral PADP., Main Limitations: It is unknown whether the negative/neutral PADP contributed to lameness or lameness resulted in lower PADP., Conclusions: Horses with hindlimb lameness localised to the distal tarsus and proximal metatarsus, but not the stifle, were more likely to have negative/neutral PADPs. Corrective farriery to improve PADP may be investigated further as one component in the treatment of hindlimb lameness localised to regions proximal to the foot. The Summary is available in Portuguese - see Supporting Information., (© 2018 EVJ Ltd.)

Background: Pituitary pars intermedia dysfunction (PPID) is a commonly described endocrine disorder in higher latitudes of the Northern hemisphere but the description of the disease at lower latitudes and in the Southern hemisphere is limited., Objectives: Document the clinical features of PPID at different Australian latitudes and climates, and investigate factors associated with survival, laminitis and insulin dysregulation (ID)., Study Design: Retrospective study of 274 equids from eight institutions across Australia., Methods: A diagnosis of PPID was based on endogenous ACTH, overnight dexamethasone suppression test, thyrotropin-releasing hormone stimulation test or necropsy. Clinical and clinicopathologic characteristics of PPID and therapeutic responses were investigated. Laminitis was diagnosed by radiographic or histologic changes and ID was diagnosed based on endogenous insulin, an oral glucose test or a 2-step insulin-response test., Results: Being a pony, having a higher body condition score and pergolide administration were associated with survival. The clinical presentation of PPID changed with latitude and climate, with anhidrosis and polyuria/polydipsia more commonly recognised at lower latitudes. Laminitis was diagnosed in 89.9% of cases and ID was present in 76.5% of cases in which they were investigated., Main Limitations: Despite the sample size, the lack of uniform testing at all locations (primary or referral cases) and the incompleteness of data sets limited the power of the statistical analyses., Conclusions: PPID can present with variable signs at different latitudes and climates, and ID should be investigated in equids diagnosed with PPID. Adequate body condition and administration of pergolide are fundamental in PPID management., (© 2018 EVJ Ltd.)

Background: Suspensory ligament branch injuries are common in horses. Most of these injuries are grouped together and considered as a single pathologic entity., Objectives: To report a specific injury of the abaxial margin of the suspensory ligament branches and to report its surgical management and outcome., Study Design: Retrospective case series., Methods: All horses with suspensory ligament branch injuries over a 9-year period (2007-2015) were identified. Horses with injuries which, on ultrasonographic examination, appeared to have defects in the abaxial margin of the suspensory ligament branch, that were subsequently confirmed during surgery were selected., Results: Twenty-nine cases fulfilled the inclusion criteria with a specific lesion location on the abaxial margin of the suspensory ligament branch. Nineteen horses raced successfully after surgery, nine returned to training but failed to race and one was lost to follow-up., Main Limitations: The absence of a comparable population of non-surgically managed horses in this study means that the contribution of removing torn tissue cannot confidently be assessed., Conclusions: The location and morphology of injuries described in this study is consistent, which suggests aetiopathogenic commonality. This case series suggests this type of injury has an identity of its own, differs from other types of suspensory ligament branch injuries and represents a previously undescribed subgroup., (© 2018 EVJ Ltd.)

Background: Iron toxicosis is rarely reported in horses and chronic excessive oral iron intake has not been reported to cause clinical symptoms in equids., Objectives: This case series describes 21 genetically unrelated horses and one donkey with chronic iron overload causing haemochromatosis and hepatopathy., Study Design: Case series., Methods: All equids showing clinical signs compatible with chronic liver disease presented to Utrecht University and diagnosed with iron overload and haemochromatosis based on histopathological evaluation of liver tissue and/or blood transferrin saturation levels of >80% and proof of excess dietary iron intake due to excess iron content in drinking water were included., Results: This study included 22 equids. All tested animals (n = 19) had transferrin saturation >80% and 21 of 22 had increased gamma-glutamyltransferase (γGT). Ultrasonography revealed rounded liver margins in five out of six horses and increased echogenicity in 4/6. Histological examination of liver tissue of 12 animals showed hepatitis, fibrosis and haemosiderin accumulation in macrophages and hepatocytes. Post-mortem examination also revealed haemosiderin accumulation in other organs in all seven examined animals. High iron content in drinking water was identified as the source of iron overload in all cases. All animals were housed under the same conditions for a minimum of 9 years prior to diagnosis of haemochromatosis. Of 22 animals, 13 survived until 1 January 2018, ranging from 17 to 79 months post diagnosis., Main Limitations: Histology of liver tissue was not available for 10 of 22 cases., Conclusions: Chronic iron overload can lead to haemochromatosis and hepatopathy in equids. Development of disease is slow and clinical signs are nonspecific. Long-term excessive iron intake in equids should be avoided. If animals drink from natural water sources, it is important to test the water for iron content. The Summary is available in Spanish - see Supporting Information., (© 2018 EVJ Ltd.)

Background: Exercise-induced pulmonary haemorrhage (EIPH) is considered a progressive disease based on histopathology, but it is unknown if tracheobronchoscopic EIPH severity worsens over time., Objectives: The aim of this study was to examine tracheobronchoscopic EIPH changes over time in a population of Thoroughbred racehorses. A secondary aim was to identify factors that affect changes in tracheobronchoscopic EIPH severity between observations., Study Design: Prospective, longitudinal, observational cross-sectional study., Methods: Thoroughbred racehorses were examined with tracheobronchoscopy no earlier than 30 min after racing. Examinations were recorded and graded blindly by experienced veterinarians using a 0-4 scale. Horses with 2 or more observations were included in the analysis. The association between the previous and current EIPH score was investigated using a linear mixed effect model. Factors associated with transitioning from a lower to a high EIPH grade and vice versa were examined using multiple ordinal regression. A semi-parametric regression model was used to examine progression using the number of career starts as a marker for time. Models were adjusted for potential confounding variables., Results: There were 2974 tracheobronchoscopic examinations performed on 747 horses. Blood was detected in over half of all examinations (55.6%). The population prevalence of EIPH increased as the number of examinations for each horse increased. The preceding EIPH score was significantly associated with the current EIPH score. Significant variables associated with moving between EIPH grades were the number of days since last racing, ambient temperature and weight carried. Tracheobronchoscopic EIPH is mildly progressive over the first thirty career starts., Main Limitations: Enrolment was voluntary. Horses were not followed for their entire career., Conclusion: Limiting the number of days in the current racing preparation and spacing races for horses with moderate to severe EIPH may be beneficial for reducing tracheobronchoscopic EIPH severity. The association between ambient temperature and EIPH warrants further investigation., (© 2018 EVJ Ltd.)

Background: Hyperinsulinaemia is the suspected component of insulin dysregulation having the strongest association with laminitis and occurs variably in equids with pituitary pars intermedia dysfunction (PPID)., Objectives: We hypothesised that magnitude of hyperinsulinaemia correlates with laminitis severity in PPID-affected equids. Furthermore, we hypothesised that owners can be unaware of chronic endocrinopathic laminitis., Study Design: Cross-sectional study., Methods: Serum insulin concentrations, owner-reported laminitis history and radiographic evidence of laminitis were determined in 38 client-owned horses and ponies with confirmed PPID. Laminitis severity was classified into four categories (normal [nonlaminitic], mild, moderate or severe laminitis) based on degree of distal phalangeal rotation. Animals were also categorised as normoinsulinaemic (<20 μU/ml), mildly hyperinsulinaemic (20-50 μU/ml) and severely hyperinsulinaemic (>50 μU/ml). One-way ANOVA, t tests and Fisher's exact tests were performed., Results: While owners reported laminitis in 37% of animals, 76% were laminitic based on study criteria (P = 0.01). Owners reported laminitis more frequently in hyperinsulinaemic vs. normoinsulinaemic animals; recognition increased with severity of hyperinsulinaemia (P = 0.03). Mean insulin concentrations were higher in equids with moderate to severe radiographic laminitis (geometric mean 74.1, 95% confidence interval (CI) 38.4-143.1 uU/ml) vs. those classified radiographically as normal to mild (31.9, 95% CI 21.1-48.1 uU/ml P = 0.03)., Main Limitations: Dynamic insulin testing was not performed; some normoinsulinaemic animals might have had subtle insulin dysregulation., Conclusions: Although radiographic abnormalities were present in most animals at the time of PPID diagnosis, chronic laminitis remained unrecognised by many owners. Owner awareness of laminitis increased with severity of hyperinsulinaemia and higher insulin concentrations were detected in association with more severe radiographic changes. The Summary is available in Chinese - See Supporting Information., (© 2018 EVJ Ltd.)