Embryology, anatomy, physiology and pathophysiology of the peritoneum and the peritoneal vasculature.

The peritoneum is a large serous membrane with both epithelial and mesenchymal features, and is essential for maintaining an intra-abdominal homeostatic equilibrium. The peritoneum plays a central role in the pathogenesis of a number of disorders. Pathological processes affecting the peritoneum such as inflammation and carcinomatosis can have serious clinical consequences, but the pathophysiology of these conditions is poorly understood. Understanding peritoneal embryology, anatomy and physiology is crucial to comprehend pathophysiological mechanisms and to devise a new focus for research. The vascular response to pathological processes appears to be of considerable importance, since the peritoneal vasculature plays a pivotal role in most associated diseases. Therefore, this review summarizes currently available literature with special emphasis on the development, anatomy and function of the peritoneal vasculature. Pathological processes are described to illustrate physiological and pathophysiological characteristics of the peritoneum.

Nonobliteration of the Processus Vaginalis. Sonography of Related Abnormalities in Children.

The objective of this pictorial essay is to systematically classify processus vaginalis­ related disorders in the light of embryology and present illustrative sonograms with corresponding diagrams. Failure of the processus vaginalis to obliterate during gestation results in a wide spectrum of anomalies, including communicating and noncommunicating hydroceles and inguinal and inguinoscrotal hernias, along with other related disorders of the genital system. There are varying classifications in the literature regarding the aforementioned entities. Proper and timely diagnosis of these entities is essential, given the differences in treatment. Although physical examination can narrow the differential diagnosis, sonography plays an essential role in establishing the diagnosis.

From anatomy to laparoscopic surgery, or how to reconcile surgeons to embryology.

PURPOSE: With the development of laparoscopy, new surgical techniques for colon resection were required. New anatomic plans of dissection were described for laparoscopic technique (medial to lateral approach) and the surgeons had to learn a complete different anatomy known as "laparoscopic anatomy". To help the surgeon through the milestones of laparoscopic colon resection, we propose an embryological and anatomical analysis of the changes of the colon and peritoneum during the foetal period to highlight the laparoscopic approach and surgical landmarks. METHODS: Seventeen human foetuses, age ranged from 7½ to 33 weeks were studied by dissections and histology. Three adult cadavers underwent laparoscopic colon surgery. RESULTS: Photographic representations of surgical views are displayed, and detailed descriptions applicable to anatomical structures are presented. CONCLUSION: Understanding the changes in the colon and peritoneum morphology leads to a clarification of the surgical technique for laparoscopic colon surgery.

Denonvilliers' fascia revisited.

Although several studies have reported that the peritoneum does not contribute to the formation of a fascia between the urogenital organs and rectum, Denonvilliers' fascia (DF), a fascia between the mesorectum and prostate (or vagina) in adults, is believed to be a remnant of the peritoneum. Remnants of the peritoneum, however, were reportedly difficult to detect in other fusion fasciae of the abdominopelvic region in mid-term fetuses. To examine morphological changes of the pelvic cul-de-sac of the peritoneum, we examined 18 male and 6 female embryos and fetuses. A typical cul-de-sac was observed only at 7 weeks, whereas, at later stages, the peritoneal cavity did not extend inferiorly to the level of the prostatic colliculus or the corresponding structure in females. The cul-de-sac had completely disappeared in front of the rectum at 8 weeks and homogeneous and loose mesenchymal tissue was present in front of the rectum at the level of the colliculus at 12-16 weeks. We found no evidence that linearly arranged mesenchymal cells developed into a definite fascia. Therefore, the development of the DF in later stages of fetal development may result from the mechanical stress on the increased volumes of the mesorectum, seminal vesicle, prostate and vagina and/or enlarged rectum. Therefore, we considered the DF as a tension-induced structure rather than a fusion fascia. Fasciae around the viscera seemed to be classified into (1) a fusion fascia, (2) a migration fascia and (3) a tension-induced fascia although the second and third types are likely to be overlapped.

Recent developments in the genetic factors underlying congenital diaphragmatic hernia.

Congenital diaphragmatic hernia (CDH) is a birth defect affecting around 1 in 3,000 births and is associated with high mortality and morbidity. It has become increasingly apparent that genetic factors underlie many forms of CDH. We review the recent developments in the area of the genetics of CDH, including potential candidate genes supported by evidence from animal models. We also discuss the possible role in the pathogenesis of CDH of defective retinoid signalling and abnormal mesenchymal cell function.

Traditional versus three-dimensional teaching of peritoneal embryogenesis: a comparative prospective study.

INTRODUCTION: Anatomy teaching is newly boosted by the development of interactive three-dimensional (3D) teaching techniques. Nevertheless, their superiority as teaching aids has never been demonstrated. The aim of this study was to compare 3D and traditional chalk teaching efficiency in terms of student memorization concerning peritoneal embryogenesis. MATERIALS AND METHODS: 165 students from the Faculties of Medicine of Sfax (Tunisia) (n = 81) and of Paris-Descartes (France) (n = 84) were taught peritoneal embryogenesis either via a 3D technique (interactive DVD ROM) (3D group, n = 85) or via the traditional chalk technique (CL group, n = 80). Both groups were subjected to an evaluation test including 34 questions distributed in six chapters at the end of the course. RESULTS: The overall rate of correct answers was higher in the 3D group (65.12 +/- 14.88 vs. 49.33 +/- 16.17%, p < 0.001). It was the same for five of the six chapters of questions excluding the chapter concerning the clinical implications (p = 0.06). There was no significant difference between 3D and CL groups regarding the 20 questions focusing on static phenomena (64.52 +/- 27.10 vs. 58.87 +/- 23.67%, p = 0.24), but the rate of correct answers was higher in the 3D group for the 14 questions focusing on dynamic phenomena (65.96 +/- 20.97 vs. 28.17 +/- 24.40%, p < 0.001). CONCLUSION: The 3D technique is significantly more efficient than the traditional chalk technique for the teaching of peritoneal embryogenesis in terms of short-term memorization and particularly for the assimilation of dynamic phenomena. Medium-term and long-term studies are needed to demonstrate that this benefit has a long-lasting impact.

Variations in Laminar Arrangements of the Mesocolon and Retropancreatic Fascia: a Histological Study Using Human Fetuses Near Term.

OBJECTIVE: The embryonic mesentery of the ascending and descending colons as well as the pancreas disappears due to peritoneal fusion, but there might be no or few photographic demonstrations of the intermediate morphologies during the process. The aims of this study were to characterize the morphological relationship of the interface between the renal fascia and peritoneum. METHODS: Fourteen late-stage fetuses with crown rump lengths (CRLs) of 250-325 mm (gestational age: 30-38 weeks) were histologically examined. RESULTS: The renal fascia, a thick or thin layer consisting of densely-distributed abundant fibers, was consistently separated from the renal capsule by a perirenal space containing fat. The transverse colon carried a typical mesocolon histologically different from the renal fascia. The ascending and descending mesocolons were irregularly divided into multiple laminae and the colic external longitudinal muscle appeared to directly contact the renal fascia. There was a spectrum of variations from multiple laminae to a single thick fascia between the pancreatic body and the left kidney or adrenal. CONCLUSIONS: A fascial development after retroperitoneal fusion of the mesentery showed great individual and site-dependent differences in proportion of 1) a complete fusion with the renal fascia and 2) a multilaminar structure including the remnant peritoneum. These variations masked the likely stage-dependent change.

Development of the human retroperitoneal fasciae.

INTRODUCTION: Although the renal fascia (RF), ureteral sheath, lateroconal fascia (LF) and hypogastric nerve are critical landmarks for retroperitoneal surgery, their laminar relationships require clarification. MATERIALS AND METHODS: Horizontal sections (hematoxylin-eosin staining) of human fetuses at two different developmental stages [9-12 (3 fetuses, crown-rump length, CRL 40-65 mm) and 20-25 weeks of gestation (9 fetuses, CRL 152-220 mm)] were compared. RESULTS: In the early-stage group, the pararenal space had already formed between the posterior RF and the transversalis fascia (TF). The anterior RF extended along the peritoneum and often fused with the latter. In the late-stage group, the posterior RF extended inferomedially toward the anterior aspect of the aorta and inferior vena cava. However, at the level of the renal hilus, the posterior RF was connected with vascular sheaths of the great vessels. The LF was seen developing as a fasciculation of the multilaminar structure in the pararenal space. However, on the posterolateral side of the colon after retroperitoneal fixation, the fusion fascia of the peritoneum could also be identified as LF. CONCLUSIONS: A common sheath for ureters and hypogastric nerves appeared to be likely on the inferior side of the kidney. The LF did not appear to be a primary structure such as the RF, but a result of secondary mechanical stress due to fatty tissue developing earlier along the TF than in the perirenal space. However, the suggested similarity between LF and fusion fascia in the plane occupied was a likely cause for misinterpreting the laminar configurations during surgery.

An investigation of the embryologic development of the fascia used as the basis for pancreaticoduodenal mobilization.

BACKGROUND: The retropancreatic fusion fascia, or fascia of Treitz, is a critical anatomical landmark during retropancreatic mobilization of the pancreatic head and duodenum (the Kocher maneuver). METHODS: Using semiserial sections from 24 human fetuses of 9-30 weeks gestation, we examined the development of this fascia. RESULTS: Retroperitoneal fixation of the pancreas occurred at around 10 weeks. Up to 20 weeks, an apparent remnant of the mesoduodenum was attached to the now-distinct renal fascia. Lymphatic vessels and follicles congregated along the ventral aspect of the fusion plane during early development. In 20- to 30-week fetuses, the duodenum began to occupy a definite position and, at the same stage, a candidate for the fascia of Treitz was seen; it was separated from the thick renal fascia by loose connective tissue. CONCLUSIONS: We hypothesize that mechanical stress during the development and growth of the duodenum causes the transformation of an indistinct remnant of the peritoneum into a distinct fascia. This mechanism is similar to that seen during the development of the renal fascia, in which the developing adrenal cortex and migrating kidney generate stress on a bundle of thin collagen fibers. Therefore, the fascia of Treitz is unlikely to be a simple remnant of the peritoneum. The fascia, if evident during surgery, should be attached to the pancreatic parenchymal side.

Development of the right colon and the peritoneal surface during the human fetal period: human ontogeny of the right colon.

BACKGROUND: Development of the digestive tract during the human fetal period has been the subject of many studies, but there are no works that study the ontogeny of both the right colon and the peritoneum. METHODS: Based on the dissections of adult male cadavers and human fetuses, the aim of this anatomical study was to demonstrate the rules of the morpho-functional group, consisting of the right colon and its peritoneum surface, in human ontogeny. RESULTS: The morphology of the right colon results from a rotational motion, inducting the migration of the cecum in the right iliac fossa and formation of the hepatic flexure. This intestinal migration is based on the axis of rotation of the spreading area of the colon at the ventral side of the lower pole of the right kidney, which becomes visible after the 17th week. CONCLUSION: Our different observations plead in favor of the peritoneal fusion theory. A few variations of this fusion can explain all the disorders in the position of the cecum-appendix that are encountered in current surgery, as well as the possibility of internal hernias.

Paradigm shift regarding the transversalis fascia, preperitoneal space, and Retzius' space.

BACKGROUND: There has been confusion in the anatomical recognition when performing inguinal hernia operations in Japan. From now on, a paradigm shift from the concept of two-dimensional layer structure to the three-dimensional space recognition is necessary to promote an understanding of anatomy. ANATOMY AND EMBRYOLOGY: Along with the formation of the abdominal wall, the extraperitoneal space is formed by the transversalis fascia and preperitoneal space. The transversalis fascia is a somatic vascular fascia originating from an arteriovenous fascia. It is a dense areolar tissue layer at the outermost of the extraperitoneal space that runs under the diaphragm and widely lines the body wall muscle. The umbilical funiculus is taken into the abdominal wall and transformed into the preperitoneal space that is a local three-dimensional cavity enveloping preperitoneal fasciae composed of the renal fascia, vesicohypogastric fascia, and testiculoeferential fascia. The Retzius' space is an artificial cavity formed at the boundary between the transversalis fascia and preperitoneal space. In the underlay mesh repair, the mesh expands in the range spanning across the Retzius' space and preperitoneal space.

Diaphragm development and congenital diaphragmatic hernia.

Advances in the understanding of normal diaphragm embryogenesis have provided the necessary foundation for novel insights into the pathogenesis of congenital diaphragmatic hernia (CDH). Although diaphragm formation is still not completely understood, we have identified key structures and periods of development that are clearly abnormal in animal models of CDH. The pleuroperitoneal fold (PPF) is a transient structure which is the target for the neuromuscular component of the diaphragm. The PPF has been shown to be abnormal in multiple animal models of Bochdalek CDH; specifically, a malformation of the nonmuscular component of this tissue is thought to underlie the later defect in the complete diaphragm. Based on data from animal models and the examination of human postmortem tissue, we hypothesize that abnormal PPF development underlies Bochdalek CDH. Further, the understanding of the pathogenesis of rarer subtypes of CDH will be advanced by the study of various new animal models discussed in this review.

[Peritoneum: a new view of the problem].

The author suggests to differentiate the concepts of "location of the organs in regard to the peritoneum" and "coverage of the organs with the peritoneum". According to the author, all the organs, except the ovaries, are located extraperitoneally, but are covered with the peritoneum from one, three or all the sides.

Serosal membranes (pleura, pericardium, peritoneum). Normal structure, development and experimental pathology.

This monograph offers a comprehensive review of the present knowledge of the structure of the serosal coverings of the pleural, pericardial, and peritoneal cavities in humans and laboratory animals. The authors provide data from their own research--with transmission and scanning electron microscopy--on the structure of the main components of the serosal membranes: mesothelial cells, underlying basal lamina, and submesothelial connective tissue layer. Two main types of mesothelial cells (flat and cubic) are distinguished and their distribution on the parietal serosal sheets and on the visceral coverings of various organs is described. The openings between mesothelial cells (stomata) and their relations with lymphatic lacunae are described thoroughly. Special reference is made to the serosal accumulations of lymphoid tissue (milky spots). The transcellular and intercellular transport to and from serosal cavities is studied by means of horseradish peroxidase tracing experiments. The prenatal and postnatal developmental studies are focused on human and rat pleura. The alterations of serosal membranes after experimental hemothorax, pneumonectomy, and peritonitis caused by Pseudomonas aeruginosa application suggest the existence of early, reversible, and late, definite periods.

Molecular evidence for multifocal papillary serous carcinoma of the peritoneum in patients with germline BRCA1 mutations.

BACKGROUND: Papillary serous carcinoma of the peritoneum (PSCP) diffusely involves peritoneal surfaces, while it spares or only superficially involves the ovaries. PSCP is histologically indistinguishable from serous epithelial ovarian carcinoma, and it may develop years after oophorectomy. The molecular pathogenesis of PSCP remains unresolved, although preliminary data suggest a multifocal origin in some cases. Patients with germline BRCA1 mutations may develop PSCP in addition to breast and ovarian carcinomas. The purpose of this study was to utilize the androgen receptor (AR) gene locus to test the hypothesis that some cases of PSCP have a multifocal origin and to determine if patients with germline BRCA1 mutations develop multifocal PSCP. METHODS: Specimens of normal and tumor tissues from 22 women with PSCP were obtained, and DNA was extracted. The AR gene locus was evaluated for patterns of loss of heterozygosity (LOH) and X-chromosome inactivation. The methylation-sensitive Hpa II restriction enzyme was used to differentiate the active and inactive X chromosomes. Germline BRCA1 mutation status of the patients was determined previously. RESULTS: Genetic analysis of tumor specimens indicated that five (23%) of 22 case subjects had patterns of selective LOH at the AR locus, consistent with multifocal, polyclonal disease origin. Two patients with selective LOH also had alternating X-chromosome inactivation patterns. Patients with germline BRCA1 mutations were more likely to have evidence of multifocal disease (two-sided Fisher's exact test, P = .01). CONCLUSIONS: Our results show that PSCP has a multifocal origin in at least some cases. Furthermore, patients with germline BRCA1 mutations are more likely to develop multifocal PSCP than are patients without BRCA1 mutations.

Long-term outcome of children with patent processus vaginalis incidentally diagnosed by laparoscopy.

INTRODUCTION: Patent processus vaginalis (PPV) might be incidentally diagnosed during laparoscopy. The aims of this study were to determine the prevalence and the natural history of PPV, i.e. its possible development into symptomatic inguinal hernia. INCLUSION CRITERIA: children <16years undergoing laparoscopy for pathologies other than processus vaginalis (PV) related, from 10/2000-10/2005. EXCLUSION CRITERIA: past or present history of PV-related pathologies. The internal inguinal rings were documented during laparoscopy. Follow-up was provided by phone inquiry and clinical examination if needed. Median follow-up was 10.5years (range 7.1-12.8). RESULTS: 416 patients were included. Median age at laparoscopy was 12.4years (range 3days-18.1years). Forty-three PPV (33 unilateral, 5 bilateral) were found in 38 patients (9.1%). Four children with PPV presented later with an ipsilateral inguinal hernia (10.5%, 95%CI [3%; 25%]), at a median age of 16.0years (range 11.8-17.3), at a median of 22.5months (range 12-50) after initial laparoscopy, as compared to no patient in the population with obliterated PV (0%, 95%CI [0%; 1%]). CONCLUSION: 9.1% of the observed pediatric population showed an asymptomatic PPV, and 10.5% of these children later developed an inguinal hernia. None of the children with obliterated PV developed a hernia.

Embryogenesis of the phrenic nerve and diaphragm in the fetal rat.

The embryogenesis of the mammalian phrenic nerve and diaphragm continues to be poorly understood. The purpose of this study was to reexamine this general issue and resolve some long-standing controversies. Specifically, we examined 1) the migratory path and the initial target for phrenic axons; 2) the relationship between the phrenic nerve and the primordial diaphragm during descent from the cervical to the thoracic spinal cord levels; and 3) the nature of the interaction between the progression of phrenic nerve intramuscular branching, myoblast and/or myogenic cell migration, and diaphragmatic myotube formation. We demonstrate that a leading group of "pioneering" phrenic axons migrate along a well-defined track of neural cell adhesion molecule (NCAM)-expressing and low-affinity nerve growth factor (p75) receptor-expressing cells to reach the primordial diaphragm, the pleuroperitoneal fold, at embryonic day (E) 13. During the next day of development, the phrenic nerve and the primordial diaphragm descend together toward the level of the thoracic spinal cord. By E14.5, intramuscular branching has commenced. There is a tight spatiotemporal correlation between the outgrowth of intramuscular phrenic nerve branches, the distribution of myoblasts and/or myogenic cells, and the formation of myotubes within the developing diaphragm, implicating intimate mutual regulation.

Distribution of the Galalpha1-3Gal antigen in cultured adult and fetal porcine pancreatic islet cells: an immunoelectron microscopic study.

The distribution of the Galalpha1-3Gal antigen (Galalpha) in cultured adult porcine islets (API) and fetal porcine pancreatic islet-like cell clusters (ICC) was studied using immunoelectron microscopy. API and ICC were cultured for 1 and 5 days, respectively, and immunogold labeled using human affinity isolated anti-Galalpha1-3Gal antibody, GS-IB4 lectin and antibodies against islet pancreatic hormones, vimentin, and von Willebrand factor. Differentiated endocrine cells were Gala-negative, but, in ICC, some immature endocrine cells were slightly Gala-positive. The Gala-expression in API was much weaker compared to ICC. In both API and ICC, the Gala antigen was expressed on duct epithelial cells, acinar cells, and endothelial cells. In ICC, strong Gala expression was observed on flattened cells covering their surfaces. These cells were identified as centroacinar cells originating from intra-islet ducts. In conclusion, although mature endocrine cells of cultured API and ICC lack the Gala-xenoantigen, several other cellular compounds are strongly Gala positive, which may contribute to xenorejection of these grafts.

Peritoneal-mediastinal leakage complication of peritoneal dialysis.

The authors report a case of mediastinal fluid collection resulting from peritoneal-mediastinal communication after continuous ambulatory peritoneal dialysis (CAPD). To the best of the authors' knowledge, this is the first reported case in the medical literature. A dry cough developed in the patient who had been receiving CAPD for 4 years. A mediastinal mass owing to peritoneal leakage of dialysate to the mediastinum was confirmed by a computed tomography scan taken 4 hours after the intraperitoneal infusion of contrast-mixed dialysate. The leakage persisted for 12 weeks after the discontinuation of CAPD fluid instillation.

Structure of the primordial diaphragm and defects associated with nitrofen-induced CDH.

The goals of this study were to further our understanding of diaphragm embryogenesis and the pathogenesis of congenital diaphragmatic hernia (CDH). Past work suggests that the pleuroperitoneal fold (PPF) is the primary source of diaphragmatic musculature. Furthermore, defects associated with an animal model of CDH can be traced back to the formation of the PPF. This study was designed to elucidate the anatomic structure of the PPF and to determine which regions of the PPF malform in the well-established nitrofen model of CDH. This was achieved by producing three-dimensional renderings constructed from serial transverse sections of control and nitrofen-exposed rats at embryonic day 13.5. Renderings of left- and right-sided defects demonstrated that the malformations were always limited to the dorsolateral portions of the caudal regions of the PPF. These data provide an explanation of why the holes in diaphragmatic musculature associated with CDH are characteristically located in dorsolateral regions. Moreover, these data provide further evidence against the widely stated hypothesis that a failure of pleuroperitoneal canal closure underlies the pathogenesis of nitrofen-induced CDH.