The mesenteric entry site as a potential weak point in gastrointestinal anastomoses - findings from an ex-vivo biomechanical analysis.

PURPOSE: Gastrointestinal disorders frequently necessitate surgery involving intestinal resection and anastomosis formation, potentially leading to severe complications like anastomotic leakage (AL) which is associated with increased morbidity, mortality, and adverse oncologic outcomes. While extensive research has explored the biology of anastomotic healing, there is limited understanding of the biomechanical properties of gastrointestinal anastomoses, which was aimed to be unraveled in this study. METHODS: An ex-vivo model was developed for the biomechanical analysis of 32 handsewn porcine end-to-end anastomoses, using interrupted and continuous suture techniques subjected to different flow models. While multiple cameras captured different angles of the anastomosis, comprehensive data recording of pressure, time, and temperature was performed simultaneously. Special focus was laid on monitoring time, location and pressure of anastomotic leakage (LP) and bursting pressures (BP) depending on suture techniques and flow models. RESULTS: Significant differences in LP, BP, and time intervals were observed based on the flow model but not on the suture techniques applied. Interestingly, anastomoses at the insertion site of the mesentery exhibited significantly higher rates of leakage and bursting compared to other sections of the anastomosis. CONCLUSION: The developed ex-vivo model facilitated comparable, reproducible, and user-independent biomechanical analyses. Assessing biomechanical properties of anastomoses offers an advantage in identifying technical weak points to refine surgical techniques, potentially reducing complications like AL. The results indicate that mesenteric insertion serves as a potential weak spot for AL, warranting further investigations and refinements in surgical techniques to optimize outcomes in this critical area of anastomotic procedures.

A case of significant loss of mesenteric fat: Educational and clinical relevance.

Mesenteric fat, a type of intraperitoneal adipose tissue, plays a critical role in protection and the immune response. Loss of mesenteric fat is a known consequence of a variety of clinical conditions; however, visual documentation of this rare occurrence is not available in the literature searched. Here we report a case of significant loss of mesenteric fat identified during educational dissection of a 79-year-old male fresh frozen donor cadaver, causing the mesenteric folds to appear transparent. The gross anatomical characteristics, clinical importance, and educational significance of this abnormality are described in this report. Knowledge of this condition may be of interest to clinicians, and documentation could benefit anatomists and educators dissecting and teaching in the laboratory setting.

CT-based diagnostic algorithm to identify bowel and/or mesenteric injury in patients with blunt abdominal trauma.

OBJECTIVES: To develop a CT-based algorithm and evaluate its performance for the diagnosis of blunt bowel and/or mesenteric injury (BBMI) in patients with blunt abdominal trauma. METHODS: This retrospective study included a training cohort of 79 patients (29 with BBMI and 50 patients with blunt abdominal trauma without BBMI) and a validation cohort of 37 patients (13 patients with BBMI and 24 patients with blunt abdominal trauma without BBMI). CT examinations were blindly analyzed by two independent radiologists. For each CT sign, the kappa value, sensitivity, specificity, and accuracy were calculated. A diagnostic algorithm was built using a recursive partitioning model on the training cohort, and its performances were assessed on the validation cohort. RESULTS: CT signs with kappa value > 0.6 were extraluminal gas, hemoperitoneum, no or moderate bowel wall enhancement, and solid organ injury. CT signs yielding best accuracies in the training cohort were extraluminal gas (98%; 95% CI: 91-100), bowel wall defect (97%; 95% CI: 91-100), irregularity of mesenteric vessels (97%; 95% CI: 90-99), and mesenteric vessel extravasation (97%; 95% CI: 90-99). Using a recursive partitioning model, a decision tree algorithm including extraluminal gas and no/moderate bowel wall enhancement was built, achieving 86% sensitivity (95% CI: 74-99) and 96% specificity (95% CI: 91-100) in the training cohort and 92% sensitivity (95% CI: 78-97) and 88% specificity (95% CI: 74-100) in the validation cohort for the diagnosis of BBMI. CONCLUSIONS: An effective diagnostic algorithm was built to identify BBMI in patients with blunt abdominal trauma using only extraluminal gas and no/moderate bowel wall enhancement on CT examination. KEY POINTS: • A CT diagnostic algorithm that included extraluminal gas and no/moderate bowel wall enhancement was built for the diagnosis of surgical blunt bowel and/or mesenteric injury. • A decision tree combining only two reproducible CT signs has high diagnostic performance for the diagnosis of surgical blunt bowel and/or mesenteric injury.

Insights on the Gut-Mesentery-Lung Axis in Pulmonary Arterial Hypertension: A Poorly Investigated Crossroad.

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by the hyperproliferation of vascular cells, including smooth muscle and endothelial cells. Hyperproliferative cells eventually obstruct the lung vasculature, leading to irreversible lesions that collectively drive pulmonary pressure to life-threatening levels. Although the primary cause of PAH is not fully understood, several studies have indicated it results from chronic pulmonary inflammation, such as observed in response to pathogens' infection. Curiously, infection by the intravascular parasite Schistosoma mansoni recapitulates several aspects of the widespread pulmonary inflammation that leads to development of chronic PAH. Globally, >200 million people are currently infected by Schistosoma spp., with about 5% developing PAH (Sch-PAH) in response to the parasite egg-induced obliteration and remodeling of the lung vasculature. Before their settling into the lungs, Schistosoma eggs are released inside the mesenteric veins, where they either cross the intestinal wall and disturb the gut microbiome or migrate to other organs, including the lungs and liver, increasing pressure. Spontaneous or surgical liver bypass via collateral circulation alleviates the pressure in the portal system; however, it also allows the translocation of pathogens, toxins, and antigens into the lungs, ultimately causing PAH. This brief review provides an overview of the gut-mesentery-lung axis during PAH, with a particular focus on Sch-PAH, and attempts to delineate the mechanism by which pathogen translocation might contribute to the onset of chronic pulmonary vascular diseases.

Association of new sonographic features with outcome in neonates with necrotizing enterocolitis.

BACKGROUND: We have recently noted some sonographic features in necrotizing enterocolitis that have received little or no attention in the current literature. These include thickening of the mesentery, hyperechogenicity of intraluminal intestinal contents, abnormalities of the abdominal wall, and poor definition of the intestinal wall. It has been our impression that the above four sonographic findings are generally seen in neonates with more severe necrotizing enterocolitis and may be useful in predicting outcome. OBJECTIVES: The aim of this study is, firstly, to review a large series of neonates, known to have clinical NEC, to document how frequently the above four sonographic features occur in neonates with necrotizing enterocolitis and, secondly, to determine whether they are predictive of outcome. MATERIALS AND METHODS: We retrospectively analyzed the clinical, radiographic, sonographic, and surgical findings in neonates with necrotizing enterocolitis between 2018 and 2021. The neonates were categorized into two groups based on outcome. Group A included neonates with a favorable outcome defined as successful medical treatment with no surgical intervention. Group B included neonates with an unfavorable outcome defined as failed medical treatment requiring surgery (for acute complications or late strictures) or death because of necrotizing enterocolitis. The sonographic examinations were reviewed with attention to the features of mesenteric thickening, hyperechogenicity of intraluminal intestinal contents, abnormalities of the abdominal wall, and poor definition of the intestinal wall. We then determined the association of these four findings with the two groups. RESULTS: We included 102 neonates with clinical necrotizing enterocolitis: 45 in group A and 57 in group B. Neonates in group B were born at a significantly earlier gestational age (median 25 weeks, range 22-38 weeks) and had a significantly lower birth weight (median 715.5 g, range 404-3120 g) than those in group A (median age 32 weeks, range 22-39 weeks, p = 0.003; median weight 1190 g, range 480-4500 g, p = 0.002). The four sonographic features were present in both study groups but with different frequency. More importantly, all four were statistically significantly more frequently present in neonates in group B compared to group A: (i) mesenteric thickening, A = 31 (69%), B = 52 (91%), p = 0.007; (ii) hyperechogenicity of intestinal contents, A = 16 (36%), B = 41 (72%), p = 0.0005; (iii) abnormalities of the abdominal wall, A = 11 (24%), B = 35 (61%), p = 0.0004; and (iv) poor definition of the intestinal wall, A = 7 (16%), B = 25 (44%), p = 0.005. Furthermore, the proportion of neonates with more than two signs was greater in group B compared to group A (Z test, p < 0.0001, 95% CI = 0.22-0.61). CONCLUSION: The four new sonographic features described were found to occur statistically significantly more frequently in those neonates with an unfavorable outcome (group B) than in those with a favorable outcome (group A). The presence or absence of these signs should be included in the sonographic report to convey the radiologists concern regarding the severity of the disease in every neonate, suspected or known to have necrotizing enterocolitis, as the findings may impact further medical or surgical management.

Viewing stromal vascular fraction de novo vessel formation and association with host microvasculature using the rat mesentery culture model.

OBJECTIVE: The objective of the study is to demonstrate the innovation and utility of mesenteric tissue culture for discovering the microvascular growth dynamics associated with adipose-derived stromal vascular fraction (SVF) transplantation. Understanding how SVF cells contribute to de novo vessel growth (i.e., neovascularization) and host network angiogenesis motivates the need to make observations at single-cell and network levels within a tissue. METHODS: Stromal vascular fraction was isolated from the inguinal adipose of adult male Wistar rats, labeled with DiI, and seeded onto adult Wistar rat mesentery tissues. Tissues were then cultured in MEM + 10% FBS for 3 days and labeled for BSI-lectin to identify vessels. Alternatively, SVF and tissues from green fluorescent-positive (GFP) Sprague Dawley rats were used to track SVF derived versus host vasculature. RESULTS: Stromal vascular fraction-treated tissues displayed a dramatically increased vascularized area compared to untreated tissues. DiI and GFP+ tracking of SVF identified neovascularization involving initial segment formation, radial outgrowth from central hub-like structures, and connection of segments. Neovascularization was also supported by the formation of segments in previously avascular areas. New segments characteristic of SVF neovessels contained endothelial cells and pericytes. Additionally, a subset of SVF cells displayed the ability to associate with host vessels and the presence of SVF increased host network angiogenesis. CONCLUSIONS: The results showcase the use of the rat mesentery culture model as a novel tool for elucidating SVF cell transplant dynamics and highlight the impact of model selection for visualization.

Vmeasur: A software package for experimental and clinical measurement of mesenteric lymphatic contractile function over an extended vessel length.

OBJECTIVE: Conventionally, in vivo mesenteric lymphatic contractile function is measured using a high magnification transmission microscope (field of view 0.3-1.5 mm), which precludes visualization of extended lengths of vessels embedded in mesenteric fat. Existing software is not optimized for imaging at a low magnification using a contrast agent. We aimed to develop a simple and clinically transferable method for in situ visualization, image analysis, and quantitative assessment of mesenteric lymphatic contractile function over an extended area. METHODS: Subserosal injection of various blue dyes was taken up by mesenteric lymphatics and visualized under a stereomicroscope (25×), allowing for video recording of 1.4 × 1.1 cm of intact mesentery. A new R package ("vmeasur") that combines multiple high-performance image analyses into a single workflow was developed. The edges of each vessel were determined by applying an automated threshold to each frame (with real-time manual verification). The vessel width at every point in each frame was plotted to provide contractile parameters over time and along the lymphatic vessel length. RESULTS: Contractile parameters and their differences along the length of the vessel were accurately calculated in a rodent model. In a human mesenteric lymphatic, the algorithm was also able to measure changes in diameter over length. CONCLUSION: This software offers a low cost, rapid, and accessible method to measure lymphatic contractile function over a wide area, showing differences in contractility along the length of a vessel. Because the presence of mesenteric fat has less of an impact on imaging, due to the use of an exogenous contrast agent, there is potential for clinical application.

Pulsatility damping in the microcirculation: Basic pattern and modulating factors.

Blood flow pulsatility is an important determinant of macro- and microvascular physiology. Pulsatility is damped largely in the microcirculation, but the characteristics of this damping and the factors that regulate it have not been fully elucidated yet. Applying computational approaches to real microvascular network geometry, we examined the pattern of pulsatility damping and the role of potential damping factors, including pulse frequency, vascular viscous resistance, vascular compliance, viscoelastic behavior of the vessel wall, and wave propagation and reflection. To this end, three full rat mesenteric vascular networks were reconstructed from intravital microscopic recordings, a one-dimensional (1D) model was used to reproduce pulsatile properties within the network, and potential damping factors were examined by sensitivity analysis. Results demonstrate that blood flow pulsatility is predominantly damped at the arteriolar side and remains at a low level at the venular side. Damping was sensitive to pulse frequency, vascular viscous resistance and vascular compliance, whereas viscoelasticity of the vessel wall or wave propagation and reflection contributed little to pulsatility damping. The present results contribute to our understanding of mechanical forces and their regulation in the microcirculation.

Bowel perforation following percutaneous sclerotherapy of an intra-abdominal lymphatic malformation.

Mesenteric lymphatic malformations result from abnormal proliferation of disorganized mesenteric lymphatic channels. Sclerotherapy is often preferred over surgery as it is less invasive and has lower post-procedure morbidity. Sclerotherapy has been described as durable and effective with a low complication rate. We describe a serious complication from sclerotherapy of a lymphatic malformation extending from the mesentery through the bowel wall, highlighting the spectrum of this pathology and the need for multidisciplinary management of complex cases.

CYSTIC LYMPHANGIOMA ARISING FROM THE SMALL INTESTINE MESENTERY INCIDENTALLY FOUND DURING SURGERY FOR A LARGE OVARIAN TUMOR - A CASE REPORT.

The aim of this study was presenting significance of diagnostic process in doctor's daily routine. A 45-year-old patient for a planned laparotomy due to left ovarian cyst detected with a routine transvaginal ultrasound. She did not report any symptoms. Computer tomography of the abdomen and pelvis showed a cystic lesion with segmental wall thick¬ening, measuring 133 ☓ 83 ☓ 135 mm, adjacent to the left ovary and the uterus on the left side. At the laparotomy exploration, a giant cyst, ca. 20 cm in diameter was found above the uterus, on the left side, in the area between the lower and middle abdomen. The histological exam results showed lymphangioma of the small and large intestine mesentery. In this case, lymphangioma was found in a rare location, in the mesentery of the ileocecal valve. It did not present any signs and symptoms. CT used in the present case failed to identify the exact point of origin of the lesion.

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 Mesentery in Complete Mesocolic Excision.

The following article summarizes technical aspects of how to operate in the mesentery during complete mesocolic excision (CME). Increasingly, CME is being adopted and as such it is important to establish the anatomical basis of the techniques involved. This review thus serves to provide that foundation and explains the surgical techniques built on it.

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.

Radiology of the Mesentery.

The recent description and re-classification of the mesentery as an organ prompted renewed interest in its role in physiological and pathological processes. With an improved understanding of its anatomy, accurately and reliably assessing the mesentery with non-invasive radiological investigation becomes more feasible. Multi-detector computed tomography is the main radiological modality employed to assess the mesentery due to its speed, widespread availability, and diagnostic accuracy. Pathologies affecting the mesentery can be classified as primary or secondary mesenteropathies. Primary mesenteropathies originate in the mesentery and subsequently progress to involve other organ systems (e.g., mesenteric ischemia or mesenteric volvulus). Secondary mesenteropathies describe disease processes that originate elsewhere and progress to involve the mesentery with varying degrees of severity (e.g., lymphoma). The implementation of standardized radiological imaging protocols, nomenclature, and reporting format with regard to the mesentery will be essential in improving the assessment of mesenteric anatomy and various mesenteropathies. In this article, we describe and illustrate the current state of art in respect of the radiological assessment of the mesentery.

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.

Intriguing Role of the Mesentery in Ileocolic Crohn's Disease.

Crohn's disease (CD) is a chronic relapsing inflammatory bowel disease with unknown etiology. Up to 80% of patients will eventually require surgery throughout their lifetime, and often repeated resections are required for disease recurrence. Observations of "creeping fat" surrounding the diseased intestine renewed interest in the mesentery, recently defined as an organ with endocrine and immune functions. According to the inside-out model, the mesentery may be primarily affected in CD and subsequent cause alterations in the mucosa. Recently, lower surgical recurrence rates have been reported with en-bloc excision of the mesentery adjoining the diseased intestine. Results of ongoing randomized controlled trials may clarify the role of the mesentery in CD and possibly lead to its adoption as standard during surgery for Crohn's disease.

Operating on the Mesentery in Robotic Colonic Surgery-General Techniques.

During colorectal surgery the mesentery is the organ on which the greatest amount of operating time is focused. It has recently gained increasing attention. This technical review focuses on the mesentery during robotic colonic procedures. Specifically, we focus upon how to access, dissect, and divide the mesentery using the robotic platform. We also touch on the management of bleeding and some specific disease etiologies.

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.

Role of the Mesentery in Crohn's Terminal Ileitis.

Despite the longstanding awareness of the presence of mesenteric alterations in Crohn's disease, the functional and clinical consequences of these alterations remain a topic of debate. Guidelines advise a limited resection without resection of the adjacent mesentery to prevent short bowel syndrome and postoperative complications. However, recently mesenteric resection has been proposed as an alternative to reduce recurrence rates in Crohn's disease patients. Here, we evaluate the data available on this topic in terminal ileitis, both from a fundamental research point of view and clinical perspective.

Mesentery in Transanal TME.

Oncological adequacy in rectal cancer surgery mandates not only a clear distal and circumferential resection margin but also resection of the entire ontogenetic mesorectal package. Incomplete removal of the mesentery is one of the commonest causes of local recurrences. The completeness of the resection is not only determined by tumor and patient related factors but also by the patient-tailored treatment selected by the multidisciplinary team. This is performed in the context of the technical ability and experience of the surgeon to ensure an optimal total mesorectal excision (TME). In TME, popularized by Professor Heald in the early 1980s as a sharp dissection through the avascular embryologic plane, the midline pedicle of tumor and mesorectum is separated from the surrounding, mostly paired structures of the retroperitoneum. Although TME significantly improved the oncological and functional results of rectal cancer surgery, the difficulty of the procedure is still mainly dependent on and determined by the dissection of the most distal part of the rectum and mesorectum. To overcome some of the limitations of working in the narrowest part of the pelvis, robotic and transanal surgery have been shown to improve the access and quality of resection in minimally invasive techniques. Whatever technique is chosen to perform a TME, embryologically derived planes and anatomical points of reference should be identified to guide the surgery. Standardization of the chosen technique, widespread education, and training of surgeons, as well as caseloads per surgeon, are important factors to optimize outcomes. In this article, we discuss the introduction of transanal TME, with emphasis on the mesentery, relevant anatomy, standard procedural steps, and importance of a training pathway.