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Recent findings related to the mesentery clarified the organisation of the abdomen at the foundational level. The Mesenteric-based model of abdominal anatomy articlulates a foundation that re-unites scientific and clinical approaches to the abdomen in health and disease. Importantly, recent advances are a reminder that we must always question dogma. The peritoneal-based dogma of conventional anatomy remained unquestioned for too long. With time, the mesenteric-based dogma will also be altered and improved on. Anatomy, and hence surgery, must always be considered as works in progress.

This article summarizes the events that shaped our current understanding of the mesentery and the abdomen. The story of how this evolved is intriguing at several levels. It speaks to considerable personal commitment on the part of the pioneers involved. It explains how scientific and clinical fields went different directions with respect to anatomy and clinical practice. It demonstrates that it is no longer acceptable to adhere unquestioningly to models of abdominal anatomy and surgery. The article concludes with a brief description of the Mesenteric Model of abdominal anatomy, and of how this now presents an opportunity to unify scientific and clinical approaches to the latter.

Recent advances in mesenteric anatomy have clarified the shape of the mesentery in adulthood. A key finding is the recognition of mesenteric continuity, which extends from the oesophagogastric junction to the mesorectal level. All abdominal digestive organs develop within, or on, the mesentery and in adulthood remain directly connected to the mesentery. Identification of mesenteric continuity has enabled division of the abdomen into two separate compartments. These are the mesenteric domain (upon which the abdominal digestive system is centered) and the non-mesenteric domain, which comprises the urogenital system, musculoskeletal frame, and great vessels. Given this anatomical endpoint differs significantly from conventional descriptions, a reappraisal of mesenteric developmental anatomy was recently performed. The following narrative review summarizes recent advances in abdominal embryology and mesenteric morphogenesis. It also examines the developmental basis for compartmentalizing the abdomen into two separate domains along mesenteric lines.

Summary Over the past 5 years, systematic investigation of the mesenteric organ has expanded and shown that the mesentery is the organ in and on which all abdominal digestive organs develop and remain connected to. In turn, this observation has clarified the anatomical foundation of the abdomen and the fundamental order at that level. Findings related to the shape and development of the mesentery have illuminated its function, advancing our understanding of the pathobiology, diagnosis, and treatment of several abdominal and systemic diseases. Inclusion of the mesentery in surgical resections alters the course of benign and malignant diseases. Mesenteric-based scoring systems can enhance the radiological interpretation of abdominal disease. Emerging findings reconcile observations across scientific and clinical fields and have been assimilated into reference curricula and practice guidelines. This Review summarises the developmental, anatomical, and clinical advances made since the mesentery was redesignated as an organ in 2016.

Background and Aims Emerging evidence points to a link between creeping fat and the pathogenesis of Crohn’s disease [CD]. Non-invasive assessment of the severity of creeping fat on cross-sectional imaging modality has seldom been investigated. This study aimed to develop and characterize a novel mesenteric creeping fat index [MCFI] based on computed tomography [CT] in CD patients. Methods MCFI was developed based on vascular findings on CT in a retrospective cohort [n = 91] and validated in a prospective cohort [n = 30]. The severity of creeping fat was graded based on the extent to which mesenteric fat extended around the intestinal circumference using the vessels in the fat as a marker. The accuracy of MCFI was assessed by comparing it with the degree of creeping fat observed in surgical specimens. The relationship between MCFI and fibrostenosis was characterized by determining if these correlated. The accuracy of MCFI was compared with other radiographic indices [i.e. visceral to subcutaneous fat area ratio and fibrofatty proliferation score]. Results In the retrospective cohort, MCFI had moderate accuracy in differentiating moderate–severe from mild fibrostenosis (area under the receiver operating characteristic [ROC] curve [AUC] = 0.799; p = 0.000). ROC analysis in the retrospective cohort identified a threshold MCFI of > 3 which accurately differentiated fibrostenosis severity in the prospective cohort [AUC = 0.756; p = 0.018]. An excellent correlation was shown between MCFI and the extent of fat wrapping in specimens in the prospective cohort [r = 0.840, p = 0.000]. Neither visceral to subcutaneous fat area ratio nor fibrofatty proliferation score correlated well with the degree of intestinal fibrosis. Conclusions MCFI can accurately characterize the extent of mesenteric fat wrapping in surgical specimens. It may become another non-invasive measure of CD fibrostenosis.

Robotic colorectal surgery is gaining popularity. The objective of this study was to compare clinical and cancer outcomes in propensity-score matched cohorts (PSM-1:1) undergoing colorectal cancer (CRC) surgery performed using laparoscopic or robotic surgery in a single institution. A PSM cohort comparison was performed in a tertiary referral cancer and National accredited rectal cancer surgery centre. Patients with CRC undergoing laparoscopic or robotic resection with curative intent from 2016 to 2019 (inclusive) were assessed for inclusion. Matched cohorts were selected using a 1:1 ratio. Statistical analysis was performed using SPSS, version 22. 128 patients were analysed [laparoscopic (n = 64); robotic (n = 64)]. Median age was 64 years (29–84 years). 55% (n = 70) of patients were male, 45% female (n = 58). SSI rates were slightly lower in the robotic group [10.9% (n = 7) v 12.5% (n = 8) p = 0.40]. Anastomotic leak rates were equal in both groups [5.4% (n = 3)]. All but one patient received an R0 resection in each group, median LNY was 14 in the robotic group and 12 in the laparoscopic group (p = 0.004) and no difference in disease recurrence (p = 0.465) or survival (p = 0.886) was observed. Structured introduction of a robotic colorectal programme over a 3-year period has resulted in equivalent outcomes with an established laparoscopic programme for CRC.

The position of abdominal organs, and mechanisms by which these are centrally connected, are currently described in peritoneal terms. As part of the peritoneal model of abdominal anatomy, there are multiple mesenteries. Recent findings point to an alternative model in which digestive organs are connected to a single mesentery. Given that direct evidence of this is currently lacking, we investigated the development and shape of the entire mesentery. Here we confirm that, within the abdomen, there is one mesentery in which all abdominal digestive organs develop and remain connected to. We show that all abdominopelvic organs are organised into two, discrete anatomical domains, the mesenteric and non-mesenteric domain. A similar organisation occurs across a range of animal species. The findings clarify the anatomical foundation of the abdomen; at the foundation level, the abdomen comprises a visceral (i.e. mesenteric) and somatic (i.e. musculoskeletal) frame. The organisation at that level is a fundamental order that explains the positional anatomy of all abdominopelvic organs, vasculature and peritoneum. Collectively, the findings provide a novel start point from which to systemically characterise the abdomen and its contents., Byrnes et al. reconstruct the developing mesentery from digitized embryonic datasets and human and animal cadavers using 3D digital and printed models. They confirm the mesentery remains a continuous organ in and on which all abdominal digestive organs develop and that at the foundation level, the abdomen comprises a mesenteric and non-mesenteric domain.

Crohn’s disease (CD) is a debilitating inflammatory bowel condition of unknown aetiology that is growing in prevalence globally. Large-scale studies have determined associations between female obesity or low body mass index (BMI) with risk of CD at all ages or 8–

The aim of this study was to quantify laparoscopic instrument use and actions of both limbs during a sample of common colorectal surgical procedures. A method was devised using Observer XT software to code video recordings. Anonymised HD video recordings of nine laparoscopic colorectal procedures performed by a single surgeon were analysed. We determined the percentage and frequency of instrument use and limb actions throughout the total laparoscopic surgical duration, as well as the duration of instrument inactivity. Seven instruments and seven actions were studied across nine surgical procedures. Manoeuvring, blunt dissection, and tenting up tissues accounted for the longest amount of total surgical time (non-dominant hand (NDH) 29%, dominant hand (DH) 39%), followed by grasping (NDH 33%, DH 9%), and cauterising (NDH

Since the first robotic assisted surgery in 1985, the number of procedures performed annually has steadily increased. Bibliometric analysis highlights the key studies that have influenced current practice in a field of interest. We use bibliometric analysis to evaluate the 100 most cited manuscripts on robotic surgery and discuss their content and influence on the evolution of the platform. The terms 'robotic surgery,' 'robot assisted surgery' and 'robot-assisted surgery' were used to search Thomson Reuters Web of Science database for full length, English language manuscripts. The top 100 cited manuscripts were analyzed by manuscript type, surgical specialty, first and last author, institution, year and journal of publication. 14,980 manuscripts were returned. Within the top 100 cited manuscripts, the majority featured urological surgery (n = 28), followed by combined results from multiple surgical subspecialties (n = 15) and colorectal surgery (n = 13). The majority of manuscripts featured case series/reports (n = 42), followed by comparative studies (n = 24). The most cited paper authored by Nelson et al. (432 citations) reviewed technological advances in the field. The year and country with the greatest number of publications were 2009 (n = 15) and the USA (n = 68). The Johns Hopkins University published the most top 100 manuscripts (n = 18). The 100 most cited manuscripts reflect the progression of robotic surgery from a basic instrument-holding platform to today's articulated instruments with 3D technology. From feasibility studies to multicenter trials, this analysis demonstrates how robotic assisted surgery has gained acceptance in urological, colorectal, general, cardiothoracic, orthopedic, maxillofacial and neuro surgery.

Background Delirium is a common neuropsychiatric disorder associated with prolonged hospital stays, and increased morbidity and mortality. Diagnosis is frequently missed due to varying disease presentation and lack of standardized testing. We examined biomarkers as diagnostic or prognostic indicators of delirium, and provide a rational basis for future studies. Method Systematic review of literature published between Jan 2000 and June 2019. Searches included: PubMed; Web of Science; CINAHL; EMBASE; COCHRANE and Medline. Additional studies were identified by searching bibliographies of eligible articles. Results 2082 relevant papers were identified from all sources. Seventy-three met the inclusion criteria, all of which were observational. These assessed a range of fourteen biomarkers. All papers included were in the English language. Assessment methods varied between studies, including: DSM criteria; Confusion Assessment Method (CAM) or CAM-Intensive Care Unit (ICU). Delirium severity was measured using the Delirium Rating Scale (DRS). Delirium was secondary to post-operative dysfunction or acute medical conditions. Conclusion Evidence does not currently support the use of any one biomarker. However, certain markers were associated with promising results and may warrant evaluation in future studies. Heterogeneity across study methods may have contributed to inconclusive results, and more clarity may arise from standardization of methods of clinical assessment. Adjusting for comorbidities may improve understanding of the pathophysiology of delirium, in particular the role of confounders such as inflammation, cognitive disorders and surgical trauma. Future research may also benefit from inclusion of other diagnostic modalities such as EEG as well as analysis of genetic or epigenetic factors.

Operation and reoperation rates for Crohn’s disease remain unacceptably high. This is despite intensive scientific and clinical investigation for several decades. Recent clinical findings indicate that inclusion of the mesentery during surgery for Crohn’s disease, may be associated with reduced requirement for re-operation. At the least, the findings indicate that resection of the mesentery is associated with slowing of disease progression. Several clinical trials have commenced aimed at further determining the effects of inclusion of the mesentery during resection. In tandem with these, several groups have identified pathobiologic links between mesenteric cellular/molecular events, and intestinal manifestations of Crohn’s disease. Collectively the findings indicate the mesentery plays a pathobiologic role in Cohn’s disease and that alterations of mesenteric inputs (whether these by surgical or pharmaco-therapeutic means) will provide novel and beneficial therapeutic strategies.

Recent updates in our understanding of human mesenteric anatomy argue in favor of re-designating the mesentery as an organ. The following chapter puts forward the current definition of the mesentery and explains how this differs from the mesentery of conventional anatomical descriptions. It then describes how our understanding of the mesentery has developed over the past 500 years up to the very present and the concept of the mesenteric organ. This is important as a review of the historical development of the mesentery optimally orientates the reader at the outset of this book.

The mesentery is a single and continuous organ. All abdominal digestive organs are directly connected to the mesenteric frame, which in turn collectively connects the abdominal digestive system to the body. It has a defined arterial inflow (via the coeliac trunk and superior and inferior mesenteric arteries) and venous drainage (at hepatic veins). Once the arterial trunks enter the mesentery they subdivide into major branches that remain intra-mesenteric until target organs are reached. The entirety of the portal venous system is intra-mesenteric in location. Mesenteric continuity and contiguity with abdominal digestive organs enables us subdivide the abdomen into mesenteric and non-mesenteric domains. This model (the mesenteric model) reconciles anatomical, embryological, surgical and radiological approaches to the abdomen. It explains how all abdominal digestive organs are centrally connected and it explains the peritoneal landscape.

There has been relatively little focus in the histological composition of the mesentery. The mesentery is now defined as the collection of tissues that maintains all abdominal digestive organs in position and in continuity with other systems. Given this definition, it is important to describe the tissues that make up the mesentery. Any such description should also include a description of the histology of associated structures. These include the peritoneal reflection a Toldt’s fascia, both of which maintain the mesentery in position.

The vascular structures contained within the mesentery are a critical conduit between the functional components of the mesenteric organ, the digestive system and the rest of the body. The architecture of the major arteries and veins that supply the abdominal organs and their relationship to the mesentery are described in this chapter. An understanding of the role that the mesentery plays as both a structural and functional component of the abdominal vascular system is emphasized.

Recent clarification of mesenteric anatomy, and demonstration of continuity, provided a new structural end-point to which human embryologists must work in explaining the development of the mesentery. This process is currently underway but there are some points that can be mentioned at this stage in the field of mesenteric organogenesis and these are summarized in the following chapter. The mesentery first emerges and subsequently remains, a single and continuous structural entity. It does not fragment or break up into multiple separate regions. All abdominal digestive organs develop within and remain closely associated with the mesentery. Digestive system organ development occurs on the mesenteric frame and this observation, in conjunction with recent anatomical advancements has led to the development of the field of mesenteric organogenesis. It is anticipated that advancements in this field will have major implications for human biology and clinical practice.

Background The structures of the mesentery including adipose tissue, nerves, and lymphatics play an important role in the pathogenesis and disease progression of Crohn’s disease (CD). Conventional surgical resection for CD usually does not involve resecting the mesentery en bloc with the specimen. This contrasts with complete mesocolic excision (CME) in colorectal cancer, which involves radical resection of the mesentery. Preliminary evidence from smaller studies suggests that applying the principle of mesocolic excision to CD surgery may reduce the risk of postoperative recurrence. This randomized controlled trial is designed to test whether applying the principles of mesocolic excision to CD results in reduced postoperative recurrence. It also aims to evaluate intra- and postoperative morbidity between the two approaches. Methods This international, multicenter, randomized controlled trial will randomize patients (n = 116) scheduled to undergo primary ileocolic resection to either receive extensive mesenteric excision (EME) or conventional ileocolic resection with limited mesenteric excision (LME). Five sites will recruit patients in three countries. In the EME group, the mesentery is resected following CME, while avoiding the root region, i.e., 1 cm from the root of the ileocolic artery and vein. In the LME group, the mesentery is retained, i.e., “close shave” or Discussion If mesocolic excision in CD reduces postoperative disease recurrence and does not increase morbidity, this trial has the potential to change practice and reduce recurrence of CD after surgical resection. Trial registration Clinical Trials.gov, ID: NCT03769922. Registered on February 27, 2019.

Adipose tissue is present in close proximity to various organs in the human body. One prominent example is fat contained in the mesentery that is contiguous with all abdominal digestive organs including the intestine. Despite the fact that mesenteric fat-wrapping around the inflamed gut (so called "creeping fat") was described as a characteristic feature of Crohn's disease (CD) in the early 1930s, the functional implications of creeping fat have received only recent attention. As a potent producer of fatty acids, cytokines, growth factors, and adipokines, creeping fat plays an important role in regulation of immunity and inflammation. Increasing evidence points to a link between creeping fat and intestinal inflammation in CD, where histopathologic evaluation shows a significant association between creeping fat and connective tissue changes in the bowel wall, such as muscular hypertrophy, fibrosis, and stricture formation. In addition, emerging mechanistic data indicate a link between creeping fat, muscularis propria hyperplasia, and stricturing disease. Information on fat-mesenchymal interactions in other organs could provide clues to fill the fundamental knowledge gap on the role of distinct components of creeping fat in intestinal fibrosis and stricture formation. Future studies will provide important new information that in turn could lead to novel therapeutic agents aimed at prevention or treatment of CD-associated fibrosis and stricture formation.

There is a paucity of methods to model soft anatomical tissues. Accurate modelling of these tissues can be difficult with current medical imaging technology. The aim of this research was to develop a methodology to model non-intestinal colorectal tissues that are not readily identifiable radiologically to enhance contextual understanding of these tissues and inform medical device design. The models created were used to inform the design of a novel medical device to separate the mesocolon from the retroperitoneum during resection of the colon. We modelled the peritoneum and the mesentery. The mesentery was used to indicate the location of Toldt’s fascia. We generated a point cloud dataset using cryosection images as the target anatomy is more visible than in CT or MRI images. The thickness of the mesentery could not be accurately determined as point cloud data do not have thickness. A denser point cloud detailing the mesenteric boundaries could be used to address this. Expert anatomical and surgical insight and point cloud data modelling methods can be used to model soft tissues. This research enhances the overall understanding of the mesentery and Toldt’s fascia in the human specimen which is necessary for medical device innovations for colorectal surgical procedures.

peer-reviewed PURPOSE: This purpose of this study was to evaluate a novel barrier ring with an assisted flow mechanism by assessing changes in peristomal moisture-associated skin damage (MASD) and perceptions of comfort, security, handling, and discretion in persons with an ileostomy for 6 months or longer. DESIGN: Single-arm, open-labeled feasibility study. SUBJECTS AND SETTINGS: Twenty participants (aged ≥18 years) with an ileostomy for 6 months or more participated in the study and 12 completed data collection. The primary reason for dropouts concerned compatibility issues with the barrier ring when used with certain convex pouching systems. METHODS: Participants used the barrier ring along with their normal ostomy pouching system for a period of 6 weeks. Changes in skin condition were assessed using the Ostomy Skin Tool (OST). Participants' perception of the barrier rings' comfort, security, handling, and discretion were also recorded on a 10-point scale, where participants would offer a low score if their experience was negative and a higher score if their experience was positive. Participants changed pouches and barrier rings at their own discretion. For participants who completed the study, the average skin condition and median ratings of comfort, security, handling, and discretion at 6 weeks were compared to baseline values. RESULTS: Twelve of the 20 participants (60%) completed the study. For those who completed, the mean score on the OST decreased from 6.2 ± 1.90 (mean ± SD) at baseline to 3.4 ±1.73 at 6 weeks, indicating a mean reduction of 2.8 (95% CI, −1.6 to −3.9; P < .001). The peristomal skin condition of 9 participants improved, whereas 3 experienced no change. All participants who completed the study rated comfort, handling, security, and discretion highly (median score 10 at baseline and at 6 weeks). CONCLUSIONS: Study findings indicate the novel ostomy barrier ring may reduce levels of peristomal MASD in persons living with an ileostomy, though a more extensive trial with a control group is recommended

Introduction The mesentery is involved in Crohn's disease. The impact of the extent of mesenteric resection on postoperative disease progression in Crohn's disease remains unconfirmed. This study aimed to determine the association between resection of the mesentery and postoperative outcomes in patients with Crohn's colitis (CC) undergoing colorectal surgery. Methods Patients with CC who underwent colorectal resection between January 2000 and December 2018 were reviewed, and the data were gathered from a prospectively maintained database. Patients were divided into 2 groups according to the extent of mesenteric resection, the extensive mesenteric excision (EME) group and the limited mesenteric excision (LME) group. Outcomes including early postoperative morbidities and surgical recurrence were compared between the 2 groups. Results Of the 126 patients included, 60 were in the LME group and 66 in the EME group. There was no significant difference between the 2 groups in early postsurgical outcomes except the intraoperative blood loss was increased in the LME group (P = 0.002). Patients in the EME group had a longer postoperative surgical recurrence-free survival time when compared with those in the LME group (P = 0.01). LME was an independent predictor of postoperative surgical recurrence (hazard ratio 2.67, 95% confidence interval 1.04-6.85, P = 0.04). This was further confirmed in the subgroup analysis of patients undergoing colorectal resection and anastomosis (hazard ratio 2.83, 95% confidence interval 1.01-7.96, P = 0.048). Discussion In patients undergoing surgery for CC, inclusion of the mesentery is associated with similar short-term outcomes and improved long-term outcomes compared with those seen when the mesentery is retained.

Surgical techniques have greatly changed and advanced with the advent of robot-assisted surgery (RAS). Patient outcome measures for RAS generally focus on patient morbidity and mortality, surgical complications, and hospital length of stay; there is limited research on patients' perceptions of RAS. Researchers conducted an integrative literature review of published research on patient experience and satisfaction after undergoing RAS. They searched nine databases and screened 1,263 articles for eligibility, six of which were critically appraised and synthesized into two main themes: patient satisfaction with RAS and the effect of information sharing on patient satisfaction. There was a dearth of qualitative studies exploring patients' perceptions after RAS and it was difficult to determine whether patient satisfaction was specifically related to the procedure modality (ie, robotic) or was influenced by other factors (eg, clinical outcomes). Clear differences between patient experience and satisfaction after undergoing RAS versus nonrobotic surgery are not apparent.

Peristomal skin complications are a common problem for persons with an ileostomy.The purpose of this pilot study was to solicit user feedback and perform an initial assessment of the performance of a new barrier seal designed to decrease the risk of chemical-induced dermatitis.Seven (7) potential participants who were at least 18 years of age,6 months post surgery, with an end or loop ileostomy and unbroken peristomal skin, and who were capable of changing their appliance themselves or had the availability of care assistance were identified and recruited by the stoma care nurse at the University Hospital, Limerick, Ireland. At the initial visit and after 1 and 2 weeks, participants were asked to rate device comfort, security, and handling; skin condition was assessed by the research nurse using the Ostomy Skin Tool. Descriptive statistics were used to tabulate the results.Five (5) participants completed the study. Discoloration, erosion, and tissue overgrowth scores improved in 3 of 5 patients, and the mean Ostomy Skin Tool score decreased from 5.4 ± 2.19 at the initial assessment to 4 ± 1.87 at the week 2 visit. Comfort, handling, and security ratings increased from a median of 8 at the beginning of the study to 10 at week 2.Initial patient feedback regarding the new product was positive, and skin assessment results suggest the new seal may help improve peristomal skin condition. Larger studies with longer patient follow-up are needed to confirm the results of this pilot evaluation.

Rates of surgery in Crohn’s disease have remained largely unchanged. Indeed, a rather substantial proportion of patients with Crohn’s disease continue to require one of more operations. In addition, the proportion requiring re-operation is also significant with rates varying between 4% and 60%.

The hindgut refers to the intestine distal to the junction between the second and third part of the transverse colon. Hindgut mobilization refers to detachment of the hindgut from its surrounding attachments. This alone is not enough to enable its resection. To enable resection, the mesentery that is contiguous with the hindgut must be also detached, and any analysis of good-quality colorectal resections will show that most operative time is spent in mobilizing the mesentery. In contrast, division and reconstitution of the intestine can be rapidly achieved, once the mesentery has been adequately released.

Restorative proctocolectomy with ileal pouch anal anastomosis (IPAA) is the surgical treatment of choice for patients with medically refractory ulcerative colitis or with familial adenomatous polyposis (FAP). Primary idiopathic pouchitis and de novo Crohn’s disease can affect the ileal pouch and cause significant morbidity. Although the cause of both is unknown, abnormalities in the pouch microbiota, coupled with a favorable genetic and immunological context, are thought to play a major pathobiological role in each. The aim of this chapter is to review the literature on the microbiota of the ileal pouch, concentrating on how disturbances of microbiota relate to pouchitis and Crohn’s disease of the pouch.

Akkermansia muciniphila utilises colonic mucin as its substrate. Abundance is reduced in ulcerative colitis (UC), as is the relative proportion of sulphated mucin in the mucus gel layer (MGL). It is unknown if these phenomena are related, however reduced sulphated mucins could contribute to reduced abundance, owing to a lack of substrate. The aim of this study was to quantify A. muciniphila within the MGL and to relate these findings with markers of inflammation and the relative proportion of sulphomucin present. Colonic biopsies and mucus brushings were obtained from 20 patients with active UC (AC), 14 with quiescent UC (QUC) and 20 healthy controls (HC). A. muciniphila abundance was determined by RT-PCR. High iron diamine alcian-blue staining was performed for histological analysis. Patients with AC had reduced abundance of A. muciniphila compared to HC and QUC. A positive association was found between A. muciniphila abundance and higher percentage of sulphated mucin (ρ 0.546, p = 0.000). Lower abundances of A. muciniphila correlated with higher inflammatory scores (ρ = 0.294 (p = 0.001)). This study confirms an inverse relationship between A. muciniphila and inflammation and a positive association between A. muciniphila abundance and percentage of sulfated mucin in the MGL.

Background: The usefulness of inflammatory indices in assessment of the severity of acute diverticulitis remains unestablished. The aim of this study was to determine whether inflammatory indices and hematological ratios could be utilised to differentiate between uncomplicated and complicated diverticulitis. Methods: Hematological and inflammatory indices were recorded for each admission with CT confirmed acute diverticulitis (101 complicated, 127 uncomplicated). Cases were divided into training (n = 57) and test sets (n = 171). A classification and regression tree (CART) analysis was employed in the training set to identify optimal inflammatory marker cut-off points associated with complicated diverticulitis. Samples (test set) were then categorized as (A) greater than and (B) less than CART identified cut-off points. The predictive properties of inflammatory marker cut-off points in distinguishing severity of diverticulitis were assessed using a univariate logistic regression analysis, summary receiver operating characteristic curves and confusion matrix generation. Results: C-reactive protein >109 mg/ml (OR 3.07, 95% CI 1.43-6.61, p = 0.004, area under the curve; AUC = 0.64) and white cell lymphocyte ratio (WLR) >17.72 (OR 4.23, 95% CI 1.95-9.17, p < 0.001, AUC = 0.64) were the most accurate parameters in distinguishing complicated and uncomplicated disease. WCC >21 × 109/l (p = 0.02, AUC = 0.60) and lymphocyte count >0.55 × 109/l (p = 0.009, AUC = 0.60) were less accurate. Conclusion: Widely used inflammatory indices are useful in the depiction of complicated diverticulitis. The indices cut-off points highlighted in this study should be considered at the time of diagnosis in combination with radiological features of complicated diverticulitis.