Future Directions.

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.

The Mesentery-Past, Present, and Future.

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.

The Development of the Mesenteric Model of Abdominal Anatomy.

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.

The Mesentery in Robot-Assisted Total Mesorectal Excision.

In recent decades, surgery for rectal cancer has evolved from an operation normally performed under poor vision with a lot of blood loss, relatively high morbidity, and mortality to a safer operation. Currently, minimally invasive rectal procedures are performed with limited blood loss, reduced morbidity, and minimal mortality. The main cause is better knowledge of anatomy and adhering to the principle of operating along embryological planes. Surgery has become surgery of compartments, more so than that of organs. So, rectal cancer surgery has evolved to mesorectal cancer surgery as propagated by Heald and others. The focus on the mesentery of the rectum has led to renewed attention to the anatomy of the fascia surrounding the rectum. Better magnification during laparoscopy and improved optimal three-dimensional (3D) vision during robot-assisted surgery have contributed to the refinement of total mesorectal excision (TME). In this chapter, we describe how to perform a robot-assisted TME with particular attention to the mesentery. Specific points of focus and problem solving are discussed.

Direct mechanical characterization of prostate tissue-a systematic review.

BACKGROUND: Direct mechanical characterization of tissue is the application of engineering techniques to biological tissue to ascertain stiffness or elasticity, which can change in response to disease states. A number of papers have been published on the application of these techniques to prostate tissue with a range of results reported. There is a marked variability in the results depending on testing techniques and disease state of the prostate tissue. We aimed to clarify the utility of direct mechanical characterization of prostate tissue in identifying disease states. METHODS: A systematic review of the published literature regarding direct mechanical characterization of prostate tissue was undertaking according to PRISMA guidelines. RESULTS: A variety of testing methods have been used, including compression, indentation, and tensile testing, as well as some indirect testing techniques, such as shear-wave elastography. There is strong evidence of significant stiffness differences between cancerous and non-cancerous prostate tissue, as well as correlations with prostate cancer stage. There is a correlation with increasing prostate stiffness and increasing lower urinary tract symptoms in patients with benign prostate hyperplasia. There is a wide variation in the testing methods and protocols used in the literature making direct comparison between papers difficult. Most studies utilise ex-vivo or cadaveric tissue, while none incorporate in vivo testing. CONCLUSION: Direct mechanical assessment of prostate tissue permits a better understanding of the pathological and physiological changes that are occurring within the tissue. Further work is needed to include prospective and in vivo data to aid medical device design and investigate non-surgical methods of managing prostate disease.

Changes in Peristomal Skin Condition and User Experience of a Novel Ostomy Barrier Ring With Assisted Flow: A 6-Week Feasibility Study.

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.

Do Inflammatory Indices Play a Role in Distinguishing between Uncomplicated and Complicated Diverticulitis?

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.

An appraisal of the computed axial tomographic appearance of the human mesentery based on mesenteric contiguity from the duodenojejunal flexure to the mesorectal level.

OBJECTIVE: The human mesentery is now regarded as contiguous from the duodenojejunal (DJ) to anorectal level. This interpretation prompts re-appraisal of computed tomography (CT) images of the mesentery. METHODS: A digital model and reference atlas of the mesentery were generated using the full-colour data set of the Visible Human Project (VHP). Seventy one normal abdominal CT images were examined to identify mesenteric regions. CT appearances were correlated with cadaveric and histological appearances at corresponding levels. RESULTS: Ascending, descending and sigmoid mesocolons were identifiable in 75%, 86% and 88% of the CTs, respectively. Flexural contiguity was evident in 66%, 68%, 71% and 80% for the ileocaecal, hepatic, splenic and rectosigmoid flexures, respectively. A posterior mesocolic boundary corresponding to the anterior renal fascia was evident in 40% and 54% of cases on the right and left, respectively. The anterior pararenal space (in front of the boundary) corresponded to the mesocolon. CONCLUSIONS: Using the VHP, a mesenteric digital model and reference atlas were developed. This enabled re-appraisal of CT images of the mesentery, in which contiguous flexural and non-flexural mesenteric regions were repeatedly identifiable. The anterior pararenal space corresponded to the mesocolon. KEY POINTS: The Visible Human Project (VHP) allows direct identification of mesenteric structures. Correlating CT and VHP allows identification of flexural and non-flexural mesenteric components. Radiologic appearance of intraperitoneal structures is assessed, starting from a mesenteric platform.

Mesenteric-Based Surgery Exploits Gastrointestinal, Peritoneal, Mesenteric and Fascial Continuity from Duodenojejunal Flexure to the Anorectal Junction--A Review.

INTRODUCTION: It is now well established that mesenteric-based colorectal surgery is associated with superior outcomes. Recent anatomic observations have demonstrated that the mesenteric organ is contiguous from the duodenojejunal to the anorectal junction. This led to similar observations in relation to associated peritoneum and fascia. The aim of this review was to demonstrate the relevance of the contiguity principle to resectional colorectal surgery. METHODS: All literature in relation to mesenteric anatomy was reviewed from 1873 to the present, without language restriction. RESULTS: Mesenteric-based surgery (i.e. complete mesocolic excision, total mesocolic and mesorectal excision) requires division of the peritoneal reflection (i.e. peritonotomy), and mesenteric mobilisation in the mesofascial plane. These are the fundamental technical elements of mesenterectomy. Mesenteric, peritoneal and fascial contiguity mean that in resectional surgery, these technical elements can be reproducibly applied at all levels from the origin at the superior mesenteric root, to the anorectal junction. CONCLUSIONS: The goals of complete mesocolic, total mesocolic and mesorectal excision can be universally achieved at any level from duodenojejunal flexure to anorectal junction, by adopting technical elements based on mesenteric, peritoneal and fascial contiguity.

The mesocolon: a histological and electron microscopic characterization of the mesenteric attachment of the colon prior to and after surgical mobilization.

BACKGROUND: Colonic mobilization requires separation of mesocolon from underlying fascia. Despite the surgical importance of planes formed by these structures, no study has formally characterized their microscopic features. The aim of this study was to determine the histological and electron microscopic appearance of mesocolon, fascia, and retroperitoneum, prior to and after colonic mobilization. METHODS: In 24 cadavers, samples were taken from right, transverse, descending, and sigmoid mesocolon. In 12 cadavers, specimens were stained with hematoxylin and eosin (3 sections) or Masson trichrome (3 sections). In the second 12 cadavers, lymphatic channels were identified by staining immunohistochemically for podoplanin. The ascending mesocolon was assessed with scanning electron microscopy. The above process was first conducted with the mesocolon in situ. The mesocolon was then surgically mobilized, and the process was repeated on remaining structures. RESULTS: The microscopic structure of mesocolon and associated fascia was consistent from ileocecal to mesorectal level. A surface mesothelium and underlying connective tissue were evident throughout. Fibrous septae separated adipocyte lobules. Where apposed to retroperitoneum, 2 mesothelial layers separated mesocolon and underlying retroperitoneum. A connective tissue layer occurred between these (ie, Toldt's fascia). Lymphatic channels were evident both in mesocolic connective tissue and Toldt's fascia. After surgical separation of mesocolon and fascia both remained contiguous, the fascia remained in situ and the retroperitoneum undisturbed. CONCLUSIONS: The findings demonstrate that the contiguous mesocolon and retroperitoneum are separated by mesothelial and connective tissue layers. These properties generate the surgical planes (ie, meso- and retrofascial planes) exploited in colonic and mesocolic mobilization.

Introducing a novel and robust technique for determining lymph node status in colorectal cancer.

OBJECTIVE: This study aims to harness the potential of public gene expression repositories, to develop gene expression profiles that could accurately determine nodal status in colorectal cancer. BACKGROUND: Currently, techniques that determine lymph node positivity (before resection) have poor sensitivity and specificity. The ability to determine lymph node status, based on preoperative biopsies, would greatly assist in planning treatment in colorectal cancer. This is particularly relevant in polyp-detected cancers. METHODS: Public gene expression repositories were screened for experiments comparing metastatic and nonmetastatic colorectal cancer. A customized graphic user interface was developed to extract genes dysregulated across most identified studies (ie, consensus profiles). The utility of consensus profiles was tested by determining whether classifiers could be derived that determined nodal positivity or negativity. Consensus profiles-derived classifiers were tested on separate Affymetrix- and Illumina-based experiments, and collated outputs were compiled in summary receiver operator curve characteristic format, with area under the curve (AUC) reflecting accuracy. The association between classification and oncologic outcome was determined using an additional, independent data set. Final validation was conducted using the Ingenuity network-linkage environment. RESULTS: Four consensus profiles were generated from which classifiers were derived that accurately determined node positive and negative status (pooled AUC were 0.79 ± 0.04 and 0.8 ± 0.03 for nodal positivity and negativity, respectively). Overall AUC ranged from 0.73 to 0.86, demonstrating high accuracy across consensus profile type, classification technique, and array platform used. As consensus profile enabled classification of nodal status, survival outcomes could be compared for those predicted node negative or positive. Patterns of disease-free and overall survival were identical to those observed for standard histopathologic nodal status. Genes contained within consensus profiles were strongly linked to the metastatic process and included (among others) FYN, WNT5A, COL8A1, BMP, and SMAD family members. CONCLUSIONS: Microarray expression data available in public gene expression repositories can be harnessed to generate consensus profiles. The latter are a source of classifiers that have prognostic and predictive properties.

A detailed appraisal of mesocolic lymphangiology--an immunohistochemical and stereological analysis.

Inadequate resection of the adjoining mesentery is associated with adverse outcome for colon cancer. Disruption of the integrity of the mesenteric lymphatic package has been implicated in this, though not proven. Recent studies have determined mesenteric anatomy and histology and now provide an opportunity to determine accurately the distribution of lymphatic vessels. The aim of this study was to characterise the distribution of the lymphatic vessels (LV) within the small intestinal and colonic mesentery, and in Toldt's fascia, which lies between the mesocolon and underlying retroperitoneum. Mesenteric samples were harvested from 12 human cadavers. Samples were taken from the small bowel mesentery, ascending, transverse, descending mesocolon and from both apposed and non-apposed portions of the mesosigmoid. Serial sections were stained immunohistochemically with monoclonal antibody D2-40 (podoplanin), and Masson's Trichrome. Lymphatic vessel (LV) density and radius of diffusion were determined using a stereological approach. A lymphatic network was embedded within the mesenteric connective tissue lattice throughout each mesenteric region. LV were identifiable within the submesothelial connective tissue where they measured 10.2 ± 4.1 µm in diameter and had an average radius of diffusion of 174.72 ± 97.68 µm. Unexpectedly, LV were identified in Toldt's fascia, where they measured 4.3 ± 3.1 µm in diameter and had a radius of diffusion of 165.12 ± 66.26 µm. This is the first study systematically to determine and quantify the distribution of lymphatic vessels within the mesenteric organ and to demonstrate the presence of such vessels within Toldt's fascia. A rich lymphatic network occupies all levels of the mesenteric connective tissue lattice. Within the latter, they are found within 0.1 mm of peritonealised mesenteric surfaces and are separated by an average distance of 0.17 mm and may be particularly vulnerable during surgery.

The effect of hysterectomy on colonoscopy completion: a systematic review and meta-analysis.

BACKGROUND: The primary aim of colonoscopy is a complete and thorough examination of the colon. There are a number of factors, however, that can potentially increase the difficulty of completing a colonoscopy. A significant proportion of women eligible for colorectal cancer screening have undergone hysterectomy. A history of hysterectomy is frequently considered to make colonoscopy more difficult, although there is no consensus in the literature. OBJECTIVE: The aim of this study is to assess the effect of hysterectomy on colonoscopy completion. DATA SOURCES: A systematic search of PubMed, Embase, and the Cochrane database identified 6 eligible studies. STUDY SELECTION: Studies that compared colonoscopy completion rates in women with a previous history of hysterectomy and women with no history of pelvic surgery were selected for review. INTERVENTION: Meta-analysis was performed by using random-effects methods. MAIN OUTCOME MEASURES: The primary outcome used was colonoscopy completion rate. The outcomes were calculated as odds ratio with 95% CI. RESULTS: A total of 5947 patients were included in the final analysis. The average hysterectomy rate was 26.3% ± 14.5%. The colonoscopy completion rate was significantly reduced in patients with a history of hysterectomy compared with those with no history of pelvic surgery (87.1% vs 95.5%) (OR, 0.28; 95% CI, 0.16-0.49; p < 0.001). Analysis of the funnel plot demonstrated nonsignificant across-study publication bias. There was significant across-study heterogeneity (Cochran Q, 19.6; p = 0.002). LIMITATIONS: The endoscopist's experience is poorly defined in some studies. Indication for colonoscopy was not provided in all cases. There is significant across-study heterogeneity. CONCLUSION: Colonoscopy completion rates appear decreased in women with a history of hysterectomy, but the available literature is heterogenous. Further studies in this area are warranted.

Overall survival is improved in mucinous adenocarcinoma of the colon.

INTRODUCTION: Debate persists regarding the relationship between mucin expression and outcome in colon cancer. This arises due to discrepancy in the definition of mucinous adenocarcinoma and the combination of both colon and rectal cancers in analyses. This study examines the relationship between increased mucin production and outcomes in colon cancer. METHODS: Cases were classified according to the World Health Organization classification of mucinous adenocarcinoma of the colon. Accordingly, tumors were categorized as either (a) mucinous adenocarcinoma of the colon (greater than 50% of the extracellular matrix occupied by mucin) or (b) non-mucinous adenocarcinoma of the colon. Overall survival and disease-free survival were calculated. A stepwise Cox proportional hazards regression model was employed to determine the risk of death/disease recurrence. Kaplan-Meier estimates of overall survival and disease-free survival were plotted for each group and compared using a log-rank test. RESULTS: On univariate analysis, mucinous adenocarcinoma was associated with reduced risk of death (P = 0.01). On multivariate analysis, mucinous adenocarcinoma was also associated with reduced risk of death (hazard ratio (HR) 0.33, 95% confidence interval (CI) 0.14-0.79, P = 0.01). Kaplan-Meier estimates confirmed improved rate of survival in the mucinous vs. non-mucinous group (P = 0.01). Mucinous adenocarcinoma did not affect disease-free survival (HR 0.75, 95% CI 0.46-1.21, P = 0.22). A comparison of Kaplan-Meier estimates for systemic recurrence demonstrated significant increases in systemic recurrence in the group with no mucin production (P = 0.04) but not for locoregional recurrence (P = 0.24). CONCLUSIONS: Histopathological evidence of mucinous adenocarcinoma in colon cancer is associated with improved outcomes.

Mesenteric-based surgery for Crohn's disease: evidence and perspectives.

Postoperative anastomotic recurrence of Crohn's disease is challenging and can lead to symptom recurrence and further surgery. The mesenteric pole of the intestine is the initial site of macroscopic anastomotic recurrence, and the mesentery may play an important role in recurrence after surgical resection. Therefore, "mesenteric-based surgery" has gained increasing attention by clinicians. However, the role of mesentery in the postoperative recurrence remains controversial. This review will examine mesenteric changes in Crohn's disease, proposed roles for mesentery in disease progression, and the potential for mesenteric-based surgery in the surgical management of Crohn disease.

Early outcomes for rectal cancer surgery in the republic of ireland following a national centralization program.

BACKGROUND: Following a national audit of rectal cancer management in 2007, a national centralization program in the Republic of Ireland was initiated. In 2010, a prospective evaluation of rectal cancer treatment and early outcomes was conducted. METHODS: A total of 29 colorectal surgeons in 14 centers prospectively collated data on all patients with rectal cancer who underwent curative surgery in 2010. RESULTS: Data were available on 447 patients who underwent proctectomy with curative intent for rectal cancer in 2010; 23.7 % of patients underwent abdominoperineal excision. The median number of lymph nodes identified was 12. The 30-day mortality rate was 1.1 %. Compared with 2007, there was a reduction in positive circumferential margin rate (15.8 vs 4.5 %, P < 0.001), clinical anastomotic leak rate (10.8 vs 4.3 %, P = 0.002), and postoperative radiotherapy use (17.8 vs 4.0 %, P < 0.001). Also, 53.9 % received preoperative radiotherapy in 2010. Four centers gave statistically more patients (high-administration), and four centers gave fewer patients (low-administration) preoperative radiotherapy for T2/T3 tumors (P < 0.05). On multivariate analysis, being treated in a "high-administration center" increased the likelihood (likelihood ratio [LR], 2.9; 95 % CI 1.7-4.8; P < 0.001) while attending a "low-administration center" (LR, 0.3; 95 % CI 0.2-0.5; P < 0.001) reduced the likelihood of receiving preoperative radiotherapy for a T2/T3 rectal cancer. CONCLUSIONS: Patients undergoing rectal cancer surgery in hospitals following a national centralization initiative received high-quality surgery. Significant heterogeneity exists in radiotherapy administration, and evidence-based guidelines should be developed and implemented.

A systematic review of preoperative duplex ultrasonography and arteriovenous fistula formation.

BACKGROUND: Arteriovenous fistula (AVF) formation for dialysis access is a common procedure. Fistula maturation is unpredictable. Preoperative duplex mapping may increase procedural success. We undertook a systematic review to assess the effect of preoperative duplex mapping on subsequent AVF patency. METHODS: The published literature was searched on PubMed and the Cochrane Library using the following keywords: 'arteriovenous fistula,' 'venous mapping,' 'ultrasound,' 'hemodialysis,' 'vascular access,' and 'perioperative vessel mapping.' Conference proceedings were hand searched for otherwise unpublished trials. Only randomized controlled trials in which preoperative duplex mapping was compared with clinical evaluation were eligible. RESULTS: Three trials (402 patients) were identified. More patients who underwent ultrasound successfully started using their fistula for dialysis access, although the difference did not reach statistical significance (174/214 vs 130/188; pooled odds ratio, 1.96; P = .11). CONCLUSIONS: Preoperative duplex mapping may improve fistula maturation rates. However, the results do not reach statistical significance and there are no cost-effectiveness data. Further work is required.