Anatomy of the mesentery: Current understanding and mechanisms of attachment

The implication of mesenteric functions and the biological effects of nanomaterials on the mesentery

A growing number of nanomaterials are being broadly used in food-related fields as well as therapeutics. Oral exposure to these widespread nanomaterials is inevitable, with the intestine being a major target organ. Upon encountering the intestine, these nanoparticles can cross the intestinal barrier, either bypassing cells or via endocytosis pathways to enter the adjacent mesentery. The intricate structure of the mesentery and its entanglement with the abdominal digestive organs determine the final fate of nanomaterials in the human body. Importantly, mesentery-governed dynamic processes determine the distribution and subsequent biological effects of nanomaterials that cross the intestine, thus there is a need to understand how nanomaterials interact with the mesentery. This review presents the recent progress in understanding the mesenteric structure and function and highlights the importance of the mesentery in health and disease, with a focus on providing new insights and research directions around the biological effects of nanomaterials on the mesentery. A thorough comprehension of the interactions between nanomaterials and the mesentery will facilitate the design of safer nanomaterial-containing products and the development of more effective nanomedicines to combat intestinal disorders.

Creeping fat formation and interaction with intestinal disease in Crohn's disease

Creeping fat (CrF), also known as fat wrapping, is a significant disease characteristic of Crohn's disease (CD). The transmural inflammation impairs intestinal integrity and facilitates bacteria translocation, aggravating immune response. CrF is a rich source of pro-inflammatory and pro-fibrotic cytokines with complex immune microenvironment. The inflamed and stricturing intestine is often wrapped by CrF, and CrF is associated with greater severity of CD. The large amount of innate and adaptive immune cells as well as adipocytes in CrF promote fibrosis in the affected intestine by secreting large amount of pro-fibrotic cytokines, adipokines, growth factors and fatty acids. CrF is a potential therapeutic target for CD treatment and a promising bio-marker for predicting response to drug therapy. This review aims to summarize and update the clinical manifestation and application of CrF and the underlying molecular mechanism involved in the pathogenesis of intestinal inflammation and fibrosis in CD.

Total colonic volvulus with a 720° twist of freely mobile colon

Segmental colonic volvulus involving the sigmoid or ileocaecal region is an important cause of large bowel obstruction and a well-established surgical emergency. Volvulus of the entire colon however is hazardously rare, in which case the diagnosis is likely to be made intraoperatively. The surgeon is then faced with the conundrum of the best surgical management, especially in the case of early intervention with viable bowel. To our knowledge this has never been reported.

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.

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.

Anatomy of the Mesentery

It is clear that despite the importance of multimodal therapy, the most impactful weapon in the arsenal of treatment in a patient with colorectal cancer is high-quality surgery. This has been shown time and time again and surgery remains the bedrock in the management of visceral, and particularly colorectal, cancer. The reason for this is an anatomical one, based upon embryological planes. One cannot truly understand and perform high-quality surgery without an appreciation of the fascial and mesenteric anatomy of the abdomen and pelvis.

R. J. (“Bill”) Heald greatly advanced the management of rectal cancer with his description of the anatomical foundation of total mesorectal excision. He popularized usage of the term “mesorectum” and was an early pioneer in the commitment to mesenteric-based surgery. This concept has been extended by Werner Hohenberger to mesocolic excision for colon cancer surgery.

These all rely on the principle that, in general, cancer tends to remain within its embryological compartment of origin, making it amenable to dissecting out as an oncological surgical envelope or package. There have been some theories put forth as to why, but it remains the fact that, far more often than not, an excision within the mesenteric plane affords better outcomes than the one that breaches it.

Thus an understanding of the anatomy of the mesentery is important and is the scientific foundation of the art that is cancer surgery.

Herein the author outlines the history of the development of our understanding of mesenteric anatomy and where we are today.

Malformation of a Mesocolon as a Cause of Colic in an Arabian Foal

This paper describes a case of partial lack of the mesocolon in a 7-month-old colt. The foal was referred to the hospital with clinical signs of severe abdominal distension of a few hours duration. Because analgesics did not relieve pain, the foal remained uncomfortable, and distension of the abdomen increased; an exploratory laparotomy was performed under general anaesthesia in dorsal recumbency. The final diagnosis was confirmed intraoperatively. During exploration of the abdominal cavity, other problems like right dorsal displacement and torsion of the colon were recognized. Correction of all problems was completed, and the mesentery was sutured. Recovery from anaesthesia was uneventful. The foal was recovering well a few months after surgery, and the owner did not complain about the results of the treatment.

Communication, collaboration and contagion: "Virtualisation" of anatomy during COVID-19

COVID-19 has generated a global need for technologies that enable communication, collaboration, education and scientific discourse whilst maintaining physical distance. University closures due to COVID-19 and physical distancing measures disrupt academic activities that previously occurred face-to-face. Restrictions placed on universities due to COVID-19 have precluded most conventional forms of education, assessment, research and scientific discourse. Anatomists now require valid, robust and easy-to-use communication tools to facilitate remote teaching, learning and research. Recent advances in communication, video conferencing and digital technologies may facilitate continuity of teaching and research activities. Examples include highly-interactive video conferencing technology, collaborative tools, social media and networking platforms. In this narrative review, we examine the utility of these technologies in supporting effective communication and professional activities of anatomists during COVID-19 and after.

Bilateral ureteral replacement using ileum in bilateral refractory ureteral stricture with renal insufficiency: a case report and review of literature

Although several studies have reported the efficacy and safety of ileal ureter in refractory ureteral strictures, reports on its long-term outcomes are still insufficient. In this case report, we present an excellent long-term outcome over three years without complication of bilateral ureteral replacement with ileum using ‘7’ shaped configuration in a woman after undergoing radical hysterectomy and radiation therapy who had renal insufficiency due to ureteral stricture. This study gave us a useful information about the feasibility and safety of bilateral ileal ureter in patients with ureteral strictures and renal insufficiency.

The Peritoneum: What Nuclear Radiologists Need to Know

The peritoneum is the largest and most complex serous membrane in the human body. The peritoneal membrane is composed of a layer of mesothelium supported by a thin layer of connective tissue. The peritoneum is one continuous sheet, forming two layers and a potential space between them - the peritoneal cavity- which is subdivided into multiple communicating spaces containing small amount of serous fluid that facilitates frictionless movement of mobile intraabdominal viscera. Peritoneum also contributes to fluid exchange mechanism and plays a role in immune response. The peritoneum is subject to many neoplastic and non-neoplastic processes including infections, trauma, developmental and inflammatory processes. Different Nuclear Medicine imaging techniques can be used to diagnose peritoneal diseases, most of these techniques can be customized depending on the clinical scenario and expected findings. Peritoneal scintigraphy can detect abnormal peritoneal communication or compartmentalization. Several nuclear medicine techniques can help characterize intraperitoneal fluid collections and differentiate sterile from infected fluid. PET imaging plays an important role in imaging of different neoplastic and non-neoplastic peritoneal pathologies. Nuclear radiologists need to be familiar with peritoneal anatomy and pathology to interpret peritoneal findings in dedicated peritoneal nuclear medicine imaging studies, as part of more general nuclear medicine scans, or on CT or MRI component of hybrid imaging studies. The purpose of this article is to review the normal peritoneal anatomy, various pathologic processes involving the peritoneum, and different nuclear medicine and hybrid imaging techniques that can help detect, characterize, and follow up peritoneal pathology.

Intramesenteric dynamic contrast pediatric MR lymphangiography: initial experience and comparison with intranodal and intrahepatic MR lymphangiography

OBJECTIVES

To report on our initial experience with intramesenteric (IM) dynamic contrast magnetic resonance lymphangiography (DCMRL) for evaluation of the lymphatics in patients with concern for mesenteric lymphatic flow disorders and to compare IM-DCMRL with intrahepatic (IH) and intranodal (IN) DCMRL.

METHODS

This is a retrospective review of imaging findings in 15 consecutive patients who presented with protein losing enteropathy (PLE) and/or ascites undergoing IM-DCMRL, IH-DCMRL, and IN-DCMRL. The IM-DCMRL technique involves the injection of a gadolinium contrast agent into the mesenteric lymphatic ducts or lymph nodes followed by imaging of the abdomen and chest with dynamic time-resolved MR lymphangiography.

RESULTS

IM-DCMRL was successfully performed in 14/15 (93%) of the patients. When comparing IN-DCMRL with IM-DCMRL, there was a significant difference in the visualization of dermal backflow (p = 0.014), duodenal perfusion (p = 0.003), duodenal leak (p = 0.014), and peritoneal leak (p = 0.003). IM-DCMRL demonstrated peritoneal leak in 7 patients in contrast to IH-DCMRL which demonstrated leak in 4 patients and IN-DCMRL which did not demonstrate any peritoneal leaks. Duodenal leaks were seen by IH-DCMRL in 9 patients versus 5 with IM-DCMRL and none with IN-DCMRL. In one patient with congenital PLE, the three modalities showed different disconnected flow patterns with duodenal leak only seen by IM-DCMRL. There were no short-term complications from the procedures.

CONCLUSIONS

IM-DCMRL is a feasible imaging technique for evaluation of the mesenteric lymphatics. In certain mesenteric lymphatic flow abnormalities, such as PLE and ascites, this imaging may be helpful for diagnosis and the planning of interventions and warrants further studies.

KEY POINTS

• Intramesenteric dynamic contrast magnetic resonance lymphangiography (IM-DCMRL) is a new imaging technique to evaluate mesenteric lymphatic flow disorders such as ascites. • IM-DCMRL is able to image lymphatic leaks in patients with ascites and protein losing enteropathy not seen with intranodal (IN-DCMRL) imaging.