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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 (tSO2), 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 tSO2 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. [ABSTRACT FROM AUTHOR]

OBJECTIVE To evaluate the use of laser Doppler flowmetry and spectrophotometry (LDFS) for large intestinal viability assessment in horses with naturally occurring large intestinal strangulations. METHODS By use of LDFS, intestinal microperfusion was quantified as tissue oxygen saturation (tSo2), hemoglobin (tHB), and blood flow (tBF) in cases with large colon volvulus and small colon strangulations undergoing colic surgery (n = 17). Intestinal biopsies were taken from the pelvic flexure in all large colon cases and in small colon cases that underwent intraoperative euthanasia. Measurements were compared between survivors and nonsurvivors, and the correlation between LDFS and (immuno)histology was tested (P < .05). RESULTS The tSo2 and tBF were clearly lower and tHB was higher than previously reported in healthy horses. Following correction of the lesion, pelvic flexure tBF was significantly lower than that of the left ventral colon. Prior to correction of the lesion, microperfusion did not differ between survivors and nonsurvivors, but following release of the strangulation the survivors had a significantly higher tSo2 and tBF compared to the nonsurvivors. There was a negative correlation between tBF and interstitium-to-crypt ratio and a positive correlation between tHB and the histological hemorrhage score. There were no significant correlations between LDFS measurements and inflammatory cell counts or hypoxia-inducible factor-1α immunoreactivity. CONCLUSIONS Large intestinal microperfusion was decreased in nonsurvivors compared to survivors and was correlated with histological injury, suggesting that LDFS has the potential to predict tissue injury and postoperative survival. CLINICAL RELEVANCE The use of LDFS as an ancillary diagnostic aid may improve intraoperative viability assessment during colic surgery. [ABSTRACT FROM AUTHOR]

Summary: Perirectal abscesses have only rarely been reported in horses. This case series describes the clinical signs, diagnosis, treatment and outcome of six horses with this condition. The equids affected were geldings or stallions of various breeds and aged from 4 months to 21 years (median age 10 months). Typical clinical signs included colic with tachycardia, tenesmus, dyschezia and abdominal distension. The diagnosis was obtained by transrectal palpation and ultrasonographic examination in five of six horses and by median laparotomy in one horse. All abscesses were located dorsally to the rectum. Rectal impaction and large colon tympany were common secondary findings. Microbiologic examination of abscess content revealed Streptococcus equi subspecies zooepidemicus in all horses. Abscesses were treated by a combination of medical and surgical approaches. One horse had to be euthanised due to complete obstruction of the pelvis by the abscess. In the other horses (5/6), the disorder was associated with an excellent prognosis. In terms of the total population of horses presenting with colic in the investigated period, the prevalence of cases with perirectal abscesses was 0.4%. Although uncommon, described cases indicate that perirectal abscesses should be considered as differential diagnosis for young and mature horses with colic signs. [ABSTRACT FROM AUTHOR]

Simple Summary: Intestinal disease with disruption of blood flow (ischaemia) is associated with a relatively high mortality rate in horses. Many investigations have focused on treatment strategies that reduce tissue injury. The sedative drug dexmedetomidine was found to precondition intestines subjected to ischaemia, resulting in reduced injury in different species, including horses. However, it remains unknown what exactly mediates this effect. Therefore, the aim of this study was to determine the effect of dexmedetomidine preconditioning with and without the administration of a drug called vatinoxan, which antagonizes the action of dexmedetomidine on the peripheral alpha2 adrenoreceptor. In 12 horses under general anaesthesia, intestinal ischaemia was implemented, followed by tissue reperfusion. Six horses received dexmedetomidine only (group Dex), while the other six horses received both dexmedetomidine and vatinoxan (DexV). Intestinal samples were taken to evaluate the degree of tissue injury, followed by a comparison between the groups. There was no difference before and directly after the disruption of tissue blood flow. After reperfusion, group DexV showed less mucosal injury compared to group Dex. There were no significant differences in programmed cell death between the treatment groups. In conclusion, antagonizing the peripheral alpha2 adrenoreceptors did not negatively affect dexmedetomidine preconditioning. Pharmacological preconditioning with dexmedetomidine has been shown to ameliorate intestinal ischaemia reperfusion injury in different species, including horses. However, it remains unknown if this effect is related to alpha2 adrenoreceptor activity. Therefore, the aim of this study was to determine the effect of dexmedetomidine preconditioning with and without the administration of the peripheral alpha2 antagonist vatinoxan. This prospective randomized experimental trial included 12 horses equally divided between two treatment groups. Horses in group Dex received a bolus of dexmedetomidine followed by a continuous rate infusion (CRI), while group DexV additionally received vatinoxan as bolus and CRI. A median laparotomy was performed under general anaesthesia, and jejunal ischaemia was applied for 90 min, followed by 30 min of reperfusion. Mucosal damage was evaluated in full thickness biopsies by use of a semiquantitative mucosal injury score and by determining the apoptotic cell counts with immunohistochemical staining for cleaved caspase-3 and TUNEL. Comparisons between the groups and time points were performed using non-parametric tests (p < 0.05). During pre-ischaemia and ischaemia, no differences could be found in mucosal injury between the groups. After reperfusion, group DexV showed lower mucosal injury scores compared to group Dex. The apoptotic cell counts did not differ between the groups. In conclusion, antagonizing the peripheral alpha2 adrenoreceptors did not negatively affect dexmedetomidine preconditioning. [ABSTRACT FROM AUTHOR]

Summary: Background: Ischaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues. Objectives: To assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability. Study design: Randomised in vivo experiment. Methods: Experimental jejunal ischaemia was induced for 90 min in horses under general anaesthesia. In the control group (C; n = 7), the jejunum was reperfused without further intervention. In the postconditioning group (IPoC; n = 7), reocclusion was implemented following release of ischaemia by clamping the mesenteric vessels in three cycles of 30 seconds. This was followed by 120 minutes of reperfusion in both groups. Intestinal microperfusion and oxygenation was measured during IPoC using spectrophotometry and Doppler flowmetry. Histomorphology and histomorphometry of the intestinal mucosa were assessed. Furthermore, electrophysiological variables and unidirectional flux rates of 3H‐mannitol were determined in Ussing chambers. Western blot analysis was performed to determine the tight junction protein levels of claudin‐1, claudin‐2 and occludin in the intestinal mucosa. Comparisons between the groups and time points were performed using a two‐way repeated measures analysis of variance (ANOVA) or non‐parametric statistical tests for the ordinal and not normally distributed data (significance P <.05). Results: IPoC significantly reduced intestinal microperfusion during all clamping cycles yet affected oxygen saturation only during the first cycle. After reperfusion, Group IPoC showed significantly less mucosal villus denudation (mean difference 21.5%, P =.02) and decreased mucosal‐to‐serosal flux rates (mean difference 15.2 nM/cm2/h, P =.007) compared to Group C. There were no significant differences between the groups for the other tested variables. Main limitations: Small sample size, long‐term effects were not investigated. Conclusions: Following IPoC, the intestinal mucosa demonstrated significantly less villus denudation and paracellular permeability compared to the untreated control group, possibly indicating a protective effect of IPoC on ischaemia reperfusion injury. [ABSTRACT FROM AUTHOR]

Background: Strangulating small intestinal lesions in the horse have increased morbidity and mortality compared to nonstrangulating obstructions due to mucosal barrier disruption and subsequent endotoxaemia. Objectives: To investigate protective effects of dexmedetomidine on small intestinal ischaemia‐reperfusion injury in the horse. Study design: Randomised, controlled, experimental study. Methods: Eighteen systemically healthy horses were randomly assigned to three groups: control, preconditioning, and post‐conditioning. During isoflurane anaesthesia, complete ischaemia was induced in a 1‐m segment of jejunum for 90 minutes. Horses in the preconditioning and post‐conditioning groups received dexmedetomidine (3.5 µg/kg followed by 7 µg/kg/h) before (preconditioning) or after beginning ischaemia (post‐conditioning), and during reperfusion. Jejunal biopsies were collected before ischaemia (baseline‐1), at the end of the ischaemic period (ischaemia), and 30 minutes after reperfusion (reperfusion‐1). Additional biopsies were taken 24 hours after reperfusion from ischaemia‐reperfusion‐injured jejunum (reperfusion‐2). Epithelial injury was scored histologically, and morphometric analyses were used to calculate villus surface area (VSA) denuded of epithelium. Data were analysed using analysis of variance, Kruskal‐Wallis and Wilcoxon two‐sample tests. Results: In the control group, epithelial injury scores and percentage of VSA denudation for ischaemia‐reperfusion‐injured jejunum were higher compared to baseline‐1 at all time points. The ischaemia and both reperfusion samples from the pre‐ and post‐conditioning groups had lower epithelial injury scores and percentage of VSA epithelial denudation compared to the control group, with no difference from baseline‐1 at any time point for the preconditioning group. Main limitations: Preconditioning has limited application in the clinical setting with naturally occurring strangulating small intestinal lesions. Conclusions: Dexmedetomidine was protective for small intestinal ischaemia‐reperfusion injury in the horse when administered before or during ischaemia. [ABSTRACT FROM AUTHOR]

Background: Pharmacological preconditioning of dexmedetomidine on small intestinal ischaemia/reperfusion injury has been reported in different animal models including horses. Objectives: The objective was to assess if xylazine and lidocaine have a preconditioning effect in an experimental model of equine jejunal ischaemia. Study design: Terminal in vivo experiment. Methods: Ten horses under general anaesthesia were either preconditioned with xylazine (group X; n = 5) or lidocaine (group L; n = 5). A historical untreated control group (group C; n = 5) was used for comparison. An established experimental model of equine jejunal ischaemia was applied, and intestinal samples were taken pre‐ischaemia, after ischaemia and following reperfusion. Histomorphological examination was performed based on a modified Chiu score. Immunohistochemical staining for cleaved caspase‐3, TUNEL and calprotectin was performed, and positive cell counts were expressed in cells/mm2. Results: There was no progression of histomorphological mucosal injury from ischaemia to reperfusion, and there were no differences in histomorphology between the groups. After ischaemia, group X had significantly less caspase‐positive cells compared to the control group with a median difference of 227% (P =.01). After reperfusion, group X exhibited significantly lower calprotectin‐positive cell counts compared to the control group, with a median difference of 6.8 cells/mm2 in the mucosa and 44 cells in the serosa (P =.02 and.05 respectively). All groups showed an increase in caspase‐ and calprotectin‐positive cells during reperfusion (P <.05). TUNEL‐positive cells increased during ischaemia, followed by a decrease after reperfusion (P <.05). Main limitations: The small sample size and the use of a historical control group. Preconditioning effects of the tested drugs may be masked by the protective effects of isoflurane in the anaesthetic protocol. Conclusions: Preconditioning with lidocaine did not have any effect on the tested variables. The lower cell counts of caspase‐ and calprotectin‐positive cells in group X may indicate a beneficial effect of xylazine on ischaemia/reperfusion injury. Due to the absence of a concurrent reduction of histomorphological injury, the clinical significance remains uncertain. [ABSTRACT FROM AUTHOR]

Objective: To compare the practicability and tissue sample quality between different intestinal biopsy techniques., Study Design: Experimental, randomized ex vivo study., Sample Population: Small intestine of nine horses., Methods: Four different biopsy techniques were evaluated in the aboral jejunum and the ileum within 1 h after euthanasia. One segment was used as control (C), and the applied techniques included an 8 mm biopsy punch (BP), transverse wedge resection (TW), longitudinal wedge resection with transverse closure (LW) and a longitudinal sample using Eppendorfer biopsy forceps (EF). Defects were closed using a single-layer continuous Lembert pattern. Duration of the procedure, intestinal diameter, contamination, and bursting pressure were determined. The quality of the obtained tissue samples for histological assessment was evaluated using a semiquantitative score. The jejunal and ileal samples were analyzed separately., Results: All biopsy procedures including defect closure were completed within 5 min, with shorter closure times for BP (p = .03). Minimal contamination could be noted in 1/8 TW and 2/8 LW cases, without significant differences between the groups. Longitudinal closure techniques (BP, EF) showed more constriction than transverse closures (TW, LW) (p < .05). Bursting pressure was >75 mmHg in all cases. Technique BP showed significantly lower biopsy quality scores (p = .009)., Conclusion: The tested biopsy techniques could all be applied effectively within a reasonable time frame, yet the biopsy punch was associated with significant artifacts and risk of missing mucosa., Clinical Significance: The findings provide insights into the possible advantages and limitations of the different techniques and alert the surgeon to potential issues with the quality of the tissue sample., (© 2024 The Author(s). Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Objectives:  The lateral trochlear ridge (LTR) of the femur is the most common predilection site for osteochondritis dissecans (OCD) in the equine stifle. The objective was to investigate the relationship between lesion size, racing performance, and sale result of Thoroughbreds with LTR OCD following arthroscopic removal as a yearling., Methods:  In this retrospective study, medical records of 145 Thoroughbreds from one equine hospital that underwent surgery for LTR OCD were reviewed; the length and depth of the lesions were measured on preoperative radiographs. Horses were allocated to group S if they were presented to a public yearling sale post-surgery, and horses in group NS were not. Each horse from group S was matched with two control horses from the same sale (group C). Influence of lesion size on racing performance and sale result was analyzed. Racing performance and sale results were compared between different categories of OCD lesion sizes and between the groups., Results:  Lesion length and depth did not affect racing performance and did not differ between group S and group NS. However, group S did perform significantly better than group NS. When comparing groups S and C, there were no significant differences in racing performance and sale result., Conclusion:  Thoroughbreds that had arthroscopic surgery for LTR OCD as a yearling and were presented on a public yearling sale performed comparable to Thoroughbreds that showed similar potential as a yearling. Sale result is not significantly affected in our study., Competing Interests: None declared., (Thieme. All rights reserved.)