T cells in the peritoneum.

The peritoneal cavity is a fluid-packed area that houses most of the abdominal organs, including the omentum, a visceral adipose tissue with milky patches or groups of leukocytes organized in the same way to those observed in typical lymphoid tissues. A distinct population of leukocytes patrols the peritoneal cavity and travels in and out of the milky spots, facing antigens or pathogens in the peritoneal fluid and responding appropriately. T cells may play a crucial function in regulating adaptive immune responses to antigens in the peritoneal cavity to ensure tissue homeostasis and healing. When peritoneal homeostasis is interrupted by inflammation, infection, obesity, or tumor metastasis, the omentum's dedicated fibroblastic stromal cells and mesothelial cells control peritoneal leukocyte recruitment and activation in unique ways. T cells, which employ their T cell receptor to target specific antigens, are an important component of the acquired immune response since they are present in the peritoneal cavity. The peritoneum provides a different environment for T cells to respond to pathogens. This chapter outlines the anatomy relevant to T cell function and biology, such as antigen processing/presentation, T cell activation, and the many T cell subpopulations in the peritoneal cavity, as well as their role in cancer or other infection.

Morphological hallmarks facilitating distinction of omental milky spots and lymph nodes: an exploratory study on their discriminative capacity.

BACKGROUND: Omental milky spots (OMSs) are the primary lymphoid structures of the greater omentum. However, the presence of lymph nodes (LNs) has occasionally been mentioned as well. Understanding which lymphoid structures are present is of significance, especially in gastric tumor metastasis; tumor deposits in omental LNs suggest local lymphatic spread, whereas tumor deposits in OMSs suggest peritoneal spread and hence extensive disease. Since LNs and OMSs share morphological characteristics and OMSs might be wrongly identified as LNs, reliable hallmarks facilitating easy discrimination are needed. MATERIALS AND METHOD: A series of microscopic morphological hallmarks unique to LNs were selected as potential candidates and were assessed for their discriminative capacity: 1) capsule, 2) trabeculae, 3) subcapsular sinus, 4) afferent lymphatic vessels, 5) distinct B- and T cell regions, and 6) a layered organization with, from the outside in a capsule, cortex, paracortex, and medulla. These hallmarks were visualized by multiple staining techniques. RESULTS: Hallmarks 1, 2 5 and 6 were shown to be the most efficient as these were consistent and discriminative. They were best visualized by Picrosirius red, smooth muscle actin and a B-cell / T-cell double staining. CONCLUSION: The presence of a capsule, trabeculae, distinct B- and T-cell regions and a layered organization represent consistent and reliable morphological features which allow to easily distinguish LNs from OMSs, especially when applied in combination.

The omentum harbors unique conditions in the peritoneal cavity to promote healing and regeneration for diaphragm muscle repair in mdx mice.

Although the primary cause of Duchenne muscular dystrophy (DMD) is a genetic mutation, the inflammatory response contributes directly to severity and exacerbation of the diaphragm muscle pathology. The omentum is a lymphoid organ with unique structural and immune functions serving as a sanctuary of hematopoietic and mesenchymal progenitors that coordinate immune responses in the peritoneal cavity. Upon activation, these progenitors expand and the organ produces large amounts of growth factors orchestrating tissue regeneration. The omentum of mdx mouse, a DMD murine model, is rich in milky spots and produces growth factors that promote diaphragm muscle regeneration. The present review summarizes the current knowledge of the omentum as an important immunologic structure and highlights its contribution to resolution of dystrophic muscle injury by providing an adequate environment for muscle regeneration, thus being a potential site for therapeutic interventions in DMD.

Earlobe-like peritoneal appendage near the angle of His: a useful landmark for demarcating the lateral margin of the gastric cardia.

The gastric cardia-the small area around the cardiac orifice including the abdominal esophagus-is an important target area for abdominal and thoracic surgeries, especially for laparoscopic procedures. In this study of 28 cadavers, a peritoneal earlobe-like appendage near the angle of His was identified as a useful indicator of the lateral margin of the abdominal esophagus, which is otherwise obscure because the peritoneum continues to the diaphragm without definite demarcation of this margin. This structure, which appears equivalent to the epiploic appendages, was commonly found to be present (in 22/28, 78.6 % of the 28 cadavers) and was 4-21 mm × 6-40 mm × 1-4 mm in size, triangular, round, or leaf-like in shape, contained fat, and was on an imaginary line along which the lesser omentum adheres to the lesser curvature and continues to the diaphragm (18/22, 81.8 %). This indicator is associated with the lesser omentum and is part of the gastrophrenic ligament, and could serve as a useful indicator of the margin of the gastric cardia, thus aiding surgeons performing laparoscopic surgery in this region.

The Omental Pedicle Flap in Dogs Revised and Refined: A Cadaver Study.

OBJECTIVE: To expand current knowledge on the canine omental vasculature and refine the existing lengthening technique of the canine omentum. STUDY DESIGN: Ex vivo study. ANIMALS: Canine cadavers (n=20). METHODS: In 10 canine cadavers the omental arteries were mapped using intravascular latex injection and these results were used to create an omental pedicle flap based on the splenic artery in 10 additional cadavers. The operating range of the flap was recorded with particular attention to the main regions of interest for omental transposition in dogs (axillary and inguinal regions). RESULTS: The superficial and deep omental leaves were each predominantly supplied by a left and a right marginal omental artery that anastomosed near the caudal omental border into a superficial and a deep omental arch, respectively. Anastomoses between arteries of the superficial and the deep omental leaves were weak and inconsistent, except for 1 anastomosis that was found in 8 of 10 dogs. By transposing the intact omentum, the right axilla could be reached in 3 dogs, both axillae in 1 dog, and both groins in all cadavers. In all cases, the omental pedicle reached to and beyond the axillary and inguinal regions. By unfolding the pedicle leaves, the width of the pedicle tip could be doubled. CONCLUSION: When lengthening the omentum is necessary to reach extra-abdominal structures, the omental pedicle flap based on the splenic artery appears to preserve the omental vascular supply. These observations warrant further clinical trials to evaluate this new omtental flap technique in vivo.

The Microscopic Structure of the Omentum in Healthy Dogs: The Mystery Unravelled.

The canine omentum has many valuable properties but is still an underestimated organ. It contributes in many ways to the protection of the peritoneal cavity through its versatility on immunological level, but also through its role during angiogenesis, absorption, adhesion and fat storage. Despite a wide range of applications, the basic structure of the omentum is not well documented. This study provides an insight in the microscopic structure of the canine omentum through both light microscopic and electron microscopic investigations. Two regions could be distinguished in the canine omentum: translucent and adipose-rich regions. The translucent regions were composed of two different layers: a continuous flattened mesothelium on top of a submesothelial connective tissue matrix. The adipose-rich regions consisted of a substantial layer of adipocytes on which a flattened continuous mesothelium was present. Between those two layers, a few strands of collagen fibres could be detected. Large aggregates of immune cells, the so-called milky spots, were not observed in the omentum of healthy dogs. Only a limited number of leucocytes, macrophages and neutrophils were found, scattered throughout the connective tissue in the translucent regions. At the level of the adipose-rich regions, the immunological population was virtually non-existent.

Cystoduodenal ligament as an abnormal fold and the accompanying anatomical and clinical implications.

This paper reports two cases of cadaveric cystoduodenal ligament in the lesser omentum, different from the commonly known hepatoduodenal and hepatogastric ligaments. Cystoduodenal ligament was occasionally reported and implies a variation in the anatomy of the omental bursa and its foramen. The omental foramen which has been commonly described to provide communication between the greater and the lesser sacs, and located posterior to the free egde of the lesser omentum, is not so in these cases. The knowledge of abnormal peritoneal folds like this may be important to surgeons, prosectors and radiologists.

Analysis of human omentum-associated lymphoid tissue components with S-100: an immunohistochemical study.

Milky spots are opaque patches in the greater omentum. They were first described by von Recklinghausen (1863) in the omentum of rabbits. In man, milky spots are relatively uniform, highly vascularized accumulations of mononuclear cells. The objective of this study was to describe in human omental lymphoid tissue components with S-100. Tissue samples (greater omentum) were collected from 14 patients operated with different reasons in our Department of General Surgery, in order to histologically present the presence of S-100 in the cells making up the milky spots in human omentum tissue. Tissue samples were cut approximately 5-8 micrometer thick with frozen-sections and stained with an indirect immunoperoxidase technique, as described previously. Then milky spots were examined by light microscopy. These data indicate that unstimulated milky spots in the human greater omentum are to a great extent just a preformed specific accumulation of primarily macrophages within the stroma of the greater omentum, secondarily B- and T-lymphocytes. In addition to these cells, we observed that a few mast and reticular cells were seen in the milky spots by S-100 reactive cross-sections of greater omentum. In the human omentum tissue that was stained with indirect immunoperoxidase method using anti S-100 monoclonal antibody, an arteriole cross-section in the center, reactive nerve cross-sections in the adjacent stroma and endogenic peroxidase reactivity in a few granulocytes in omental tissue were observed.

The omentum: anatomical, metabolic, and surgical aspects.

INTRODUCTION: The omentum is acknowledged to have diverse functions in the pathophysiology of intra-abdominal disease. Its angiogenic properties act as a natural defense mechanism in peritonitis and intra-abdominal sepsis. With advancing technology the omentum is revealing itself as a new player in the field of molecular surgery with special reference to cancer, obesity and tissue reconstruction. MATERIALS AND METHODS: This article reviews the existing and potential surgical applications of the omentum.

Pathways of abdominal tumour spread: the role of the subperitoneal space.

The subperitoneal space is a large, unifying, anatomically continuous potential space that connects the peritoneal cavity with the retroperitoneum. This space is formed by the subserosal areolar tissue that lines the inner surfaces of the peritoneum and the musculature of the abdomen and pelvis. It contains the branches of the vascular, lymphatic, and nervous systems that supply the viscera. The subperitoneal space extends into the peritoneal cavity and is invested between the layers of the mesenteries and ligaments that support and interconnect the abdominal and pelvic organs. As such, it provides one large continuous space in which infectious, neoplastic, inflammatory, and hemorrhagic disease may spread in many directions.

[Left hepatic artery: anatomical variations and clinical implications]. / L'artère hépatique gauche, variations anatomiques et implications cliniques.

The presence of a left hepatic artery (LHA) is an anatomical variation related to the persistence after fetal maturation of one of the two embryonic hepatic arteries, who disappear in the modal liver arterial vascularisation (liver vascularisation by a unique hepatic artery originating from the celiac trunk). When present, LHA is originating from the left gastric artery and runs through the pars condensa of the lesser omentum. Its frequency is varying from 12 to 34% according to the different study methods: 14 to 27% in anatomical series, 12 to 20% in angiographic studies and 12 to 24% in liver transplantation series. Laparoscopic detection has the highest sensitivity with reported rates from 18 to 34% of cases. LHA is irrigating a variable liver territory from a part of the left lobe to the whole liver in less than 1% of cases. A satisfactory knowledge of these anatomical variations is mandatory in liver surgery and during liver transplantation but also each time the pars condensa is approached during gastric surgery, hiatal surgery for gastroesophageal reflux and for bariatric surgery. Due to existing anastomosis between liver arteries, LHA ligation is feasible in most cases with a subsequent and transitory elevation of liver enzymes. On the contrary, in case of a unique LHA for the whole liver, the safety of its ligation is not demonstrated.

A study of multi-detector row CT scan on greater omentum in 50 individuals: correlating with anatomical basis and clinical application.

BACKGROUND: In view of the descriptions of the CT manifestations on the greater omentum (GO) were not precise and detailed enough in the previous literature, we tried to evaluate the radiologic-anatomical features of the GO and to address the related clinical implications for the radiologic diagnosis and surgical application. METHODS: We evaluated the GO by using multi-detector row CT (MDCT) scanning in 50 individuals correlating with anatomical basis and clinical application. Emphasis was placed on the following items: the anatomical distribution and location of the GO; the CT manifestations of the vasculature, fatty tissue and lymph nodes. RESULTS: The gastro-epiploic vessel, the landmark for delineating the GO, was visualized in 50/50 cases (100%). The gastro-colic vein was detected in 34/50 cases (68%). The free-hanging portion, 48 cases revealed, seemed to have the capability of 'migration': it is located in the subphrenic spaces in 9/48 cases (19%) and distributed in the right lower quadrant predominantly in 10/48 cases (21%). Three-dimensional reformatted images, obtained in five cases, demonstrated the return of the gastro-epiploic vein distinctly. Lymph nodes were rarely detected within the GO. CONCLUSION: The depicted omental vessels, visualized by using multi-planar reconstruction images together with three-dimensional reformatted images, played a crucial role in delineating the GO comprehensively. It can provide the valuable data for the radiologic diagnosis and surgical therapy planning including surgery of reconstruction, pancreas, portal hypertension as well as infections and neoplastic diseases.

Anatomical Description of the Liver, Hepatic Ligaments and Omenta in the Coypu (Myocastor coypus) / Descripción Anatómica del Hígado, Ligamentos hepáticos y Omentos en el Coipo (Myocastor coypus)

The objective of this work is to give a complementary description of the hepatic lobulation, the hepatic ligaments and the omenta of the nutria. Thirty nutrias were studied by gross dissection. The liver of the nutria was divided into six lobules as follows: left lateral, left medial, quadrate, right medial, right lateral, and caudate lobes. The caudate lobe was divided into a papillary and a caudate process. A whole falciform ligament, extending as far as the navel, was found in all animals. This one was the only ligament that contained fat in between its sheets, and it was abundant in the umbilical part. The left triangular ligament had two parts. One of them was attached to the left lateral lobe of the liver and the other one to the left medial lobe. The right triangular ligament also was double. The lateral triangular ligaments where larger than the medial ones. The hepatorenal ligament it was attached to the right kidney and its ventral free border measured 3.0 cm. The coronary ligament was always relatively well marked and was continuous with all the previous ligaments. The omenta were similar to those described for the rabbit but had more fat. The greater omentum united with the left sheet of the mesoduodenum and to the ascending mesocolon.

El objetivo de este trabajo es complementar las descripciones de la lobulación hepática, los ligamentos hepáticos y los omentos de la nutria. Treinta nutrias fueron estudiadas mediante disección simple. El hígado de la nutria estaba dividido en seis lóbulos: lóbulos lateral izquierdo, medial izquierdo, cuadrado, medial derecho, lateral derecho y caudado. El lóbulo caudado estaba dividido en proceso papilar y proceso caudado. Un ligamento falciforme completo, extendido hasta el ombligo, fue hallado en todos los animales. Este era el único ligamento que tenía grasa entre sus hojas, la cual era abundante en la parte umbilical. El hgamento triangular izquierdo estaba compuesto por dos partes. Una parte se fijaba al lóbulo lateral izquierdo y la otra al lóbulo medial izquierdo del hígado. El hgamento triangular derecho también era doble. Los hgamentos triangulares laterales eran más grandes que los mediales. El hgamento hepatorrenal estaba unido al riñon derecho y medía 3,0 cm en su borde hbre ventral. El ligamento coronario era siempre relativamente marcado y se continuaba con todos los ligamentos anteriores. Los omentos eran similares a los descritos para el conejo pero más cargados de grasa. El omento mayor se unía a la hoja izquierda del mesoduodeno y al mesocolon ascendente.

Modified Mallampati test, thyromental distance and inter-incisor gap are the best predictors of difficult laryngoscopy in West Africans.

PURPOSE: To determine the ability to predict difficult visualization of the larynx (DVL) from the following preoperative airway predictive indices, in isolation and combination: modified Mallampati test (MMT), thyromental distance (TMD), sternomental distance (SMD), horizontal length of the mandible (HLM) and inter-incisor gap (IIG). METHODS: Three hundred and eighty consecutive patients undergoing general anesthesia were evaluated using the MMT, TMD, SMD, HLM and IIG and the cut-off points for the airway predictors were Mallampati III and IV; < or = 6.5 cm, < or = 13.5 cm, < or = 9.0 cm and < or = 4.0 cm respectively. During direct laryngoscopy, the laryngeal view was graded using the Cormack and Lehane (CL) classification. CL grades III and IV were considered difficult visualization. Sensitivity, specificity and positive predictive value for each airway predictor in isolation and in combination were determined. Logistic regression analysis was used to determine independent predictors of DVL. RESULTS: Difficulty to visualize the larynx was found in 13 (3.4%) patients. The sensitivity, specificity and the positive predictive value for the five airway predictors were: MMT (61.5%; 98.4%; 57.1%), TMD (15.4%; 98.1%; 22.2%), SMD (0%; 100%; 0%), HLM (30.8%, 76.0%; 4.3%) and IIG (30.8%; 97.3%; 28.6%). The best combination of predictors was MMT/TMD/IIG with a sensitivity, specificity and positive predictive value of 84.6%; 94.6%; 35.5% respectively. Logistic regression analysis showed that weight, MMT, IIG and TMD were independent predictors of DVL. CONCLUSION: MMT, TMD and IIG appear to provide the optimal combination in prediction of DVL in a West African population.

Gene expression profile of omental adipose tissue in human obesity.

The aim of the present study was to gain insight into the pathophysiology of obesity by comparing the pattern of gene expression of omental adipose tissue of obese and lean volunteers using DNA microarrays. Omental adipose tissue biopsies were obtained by laparoscopic surgery from six male patients (44.2+/-6.3 yr). RNA was extracted and pooled for the obese (BMI: 37.3+/-2.5 kg/m2) and lean (BMI: 23.4+/-0.8 kg/m2) groups. From the total number of genes analyzed (1,152 well-characterized human genes), 41% were expressed at sufficient levels in human adipose tissue for detection in the microarray experiments, finding that 89 genes were up-regulated while 64 were down-regulated at least twofold in the omental adipose tissue obtained from obese patients. We found a general tendency to blunt lipolysis inducer genes and a global down-regulation of genes encoding growth factors. Moreover, an up-regulation in the expression of several mitogen-activated protein kinases (MAPKs) was observed. The down-regulation of genes involved in lipolysis activation may be involved in the etiopathogenesis of obesity. In addition, down-regulation of growth factors and the up-regulation of MAPKs may indicate an attempt to restrain adipocyte proliferation and differentiation. Furthermore, obesity is accompanied by an altered expression in omental adipose tissue of genes involved not only in energy homeostasis but also in quite diverse biological functions, such as immune response. The genomic approach underlines the importance of adipose tissue beyond energy metabolism.

Omental transposition for low pelvic anastomoses.

Surgeons' opinions differ regarding the role of the omentum in low pelvic intestinal anastomoses. This study was undertaken to define the anatomy and surgical technique of omental transposition to the pelvis. We studied 45 cadavers to elucidate surgical aspects of omental mobilization, lengthening, and transposition into the pelvic cavity. In addition, intraoperative studies of omental transposition to the pelvis were performed in 20 patients with chronic ulcerative colitis, familial adenomatous polyposis, and rectal cancer who were undergoing ileal J-pouch anal anastomosis or low anterior resection. The most important anatomic variables for omental transposition are three variants of arterial blood supply: (1) In 56% of patients, there is one right, one (or two) middle, and one left omental artery. (2) In 26% of patients, the middle omental artery is absent. (3) In the remaining 18% of patients, the gastroepiploic artery is continued as a left omental artery but with various smaller connections to the right or middle omental artery. The first stage of omental lengthening is detachment of the omentum from the transverse colon mesentery. This must be performed carefully, as the omentum is closely adherent to the right transverse mesocolon. The second stage is the actual lengthening of the omentum. The third stage is placement of the omental flap into the pelvis. Creation of an omental pedicle is a simple surgical procedure. This procedure can be performed quickly, does not involve significant blood loss, and may reduce the frequency of complications after low pelvic anastomoses.

[The dislocation of the omentum into the right pleural cavity]. / Dislokatsiia sal'nika v pravuiu plevral'nuiu polost'.

The author presents results of a topographo-anatomical investigation aimed at studying and proving the optimum way of dislocation of a greater omentum flap into the pleural cavity in order to improve processes of regeneration of the bronchus stump. A flap of the omentum with the saved right gastro-omental artery was used. The esophageal foramen of the diaphragm, right sternocostal triangle were considered as possible ways of dislocation as well as the artificially made foramina in the tendinous center of the right half of the diaphragm.

The insertion of the lesser and greater gastric omenta and its significance for the T classification of gastric carcinomas (UICC).

The problem of T classification of proximal gastric carcinomas is becoming increasingly important due to a rise in the incidence of these tumors. The aim of this study was to examine the gastric insertion of the lesser and greater omenta and its role in the T classification of gastric carcinomas. The stomach and greater and lesser omenta were removed from 76 fixed cadavers and 12 measurements each were done in defined localizations. The lesser omentum extended to the gastric wall in 98% of the cases. This junction as well as the omental thickness and thus the retroperitoneal part are especially pronounced in the cardiac region. According to the current UICC classification, even advanced tumors extending into the gastric wall can be classified T2 as long as they do not penetrate the visceral peritoneum. This results in "understaging" and a seemingly poorer prognosis for cardiac carcinomas. Our study results support the recommendation of Hermanek and Wittekind [5] to subdivide the T2 stage of gastric carcinomas on the basis of infiltration depth.