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.

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.

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.

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.

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.

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.

Pax3 gene expression is not altered during diaphragmatic development in nitrofen-induced congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Malformations of the pleuroperitoneal folds (PPFs) have been identified as the origin of the diaphragmatic defect in congenital diaphragmatic hernia (CDH). Pax3, expressed in muscle precursor cells (MPCs), plays a key role in regulating myogenesis and muscularization in the fetal diaphragm. Pax3 mutant mice display absence of muscular diaphragm. However, the distribution of muscle precursor cells is reported to be normal in the PPF of the nitrofen-CDH model. We designed this study to investigate the hypothesis that Pax3 gene expression is unaltered in the PPF and developing diaphragm in the nitrofen-induced CDH model. METHODS: Pregnant rats were treated with nitrofen or vehicle on gestational day (D) 9 and sacrificed on D13, D18, and D21. Pleuroperitoneal folds (D13) and developing diaphragms (D18 and D21) were dissected, total RNA was extracted, and real-time quantitative polymerase chain reaction was performed to determine Pax3 messenger RNA levels. Confocal immunofluorescence microscopy was performed to evaluate protein expression/distribution of Pax3. RESULTS: Relative messenger RNA expression levels of Pax3 in PPFs and developing diaphragms were not significantly different in the nitrofen group compared with controls. Intensity of Pax3 immunofluorescence was also not altered in PPFs and developing diaphragms of the nitrofen group compared with controls. CONCLUSION: Pax3 gene expression is not altered in the PPFs and developing diaphragm of nitrofen-CDH model, suggesting that the diaphragmatic defect is not caused by disturbance of myogenesis and muscularization.

Peritoneal bands: a review of anatomical distribution and clinical implications.

The complexity of embryological development of the gastrointestinal tract and mesentery provides a platform for the formation of a wide variety of variant veils, folds, and membranes, collectively termed peritoneal bands. These structures, which represent anatomically unabsorbed portions of the omentum and mesentery, although often benign, have the potential to cause clinically significant manifestations in both the neonate and adult. Although these deviant structures may be identified over a broad range of the abdominal cavity, they are most commonly identified in the regions of the duodenum, duodenojejunal flexure, ileocecal junction, and ascending colon. As a result of the diverse location of these variant structures, clinical manifestations are highly variable, ranging from acute presentations of intestinal necrosis as a result of strangulated midgut volvulus to chronic, vague abdominal pain. This article seeks to highlight the importance of a thorough anatomical understanding of the distribution of the various abnormal peritoneal folds, bands, and ligaments, which may result from aberrations in embryonic gastrointestinal development and their respective clinical implications. Moreover, to advance the knowledge of peritoneal bands, this article discusses the appropriate diagnostic studies and treatment interventions required for these variant structures.

Fetal topographical anatomy of the upper abdominal lymphatics: its specific features in comparison with other abdominopelvic regions.

Using semiserial sections from 19 human fetuses of 8-30 weeks gestation, we examined the topohistology of the upper abdominal lymphatics and compared it with that of the lower abdominal and pelvic lymphatics. The upper abdominal lymphatics were characterized by an intimate relationship with the peritoneal lining, a common mesentery for the celiac trunk and superior mesenteric artery (SMA). Lymphatic connections from the upper abdominal viscera to the paraaortic and paracaval areas followed two routes: (1) from the intestinal mesentery, along the peritoneum on the left aspect of the proximal SMA, via the chain of lymph follicles (LFs) lying along the retropancreatic fusion fascia, to drain into the LFs around the left renal vein; (2) from sites along the peritoneum on the posterior wall of the omental bursa, via the root of the hepatoduodenal ligament, to drain into LFs around the vena cava. The development of these two posterior drainage routes seemed to be promoted by the peritoneum or a peritoneal remnant (i.e., fusion fascia) attaching to the great vessels, and inhibited or impeded by the developing nerves and diaphragm. No paraaortic, paracaval, or pelvic LFs lay along the peritoneum. The pelvic LFs were usually located along the bundle of lymphatic vessels originating from the femoral canal.

The embryology of the diaphragm.

Despite the progress in prenatal diagnosis and intervention as well as postnatal therapeutic strategies, congenital diaphragmatic hernia (CDH) is still associated with a meaningful mortality because of the induced pulmonary hypoplasia. An essential key in understanding the pathogenesis of CDH is the underlying embryology, which has been neglected during the last decades. Likewise, the development of the normal diaphragm is still poorly understood. Obsolescent perceptions, mainly formed from histologic sections, are still propagated. In this review we present an atlas of scanning electron microscopy images that depict the normal and defective development of the diaphragm in the nitrofen rat model for CDH. Our findings suggest that the normal diaphragm mainly develops from the posthepatic mesenchymal plate. If the development of the posthepatic mesenchymal plate is impaired, a diaphragmatic defect occurs.

Ten-year review of groin laparoscopy in 1001 pediatric patients with clinical unilateral inguinal hernia: an improved technique with transhernia multiple-channel scope.

PURPOSE: The purpose of this 10-year review of data is to verify the effectiveness, safety, and appropriate age group for using a multichannel scope during inguinal herniorrhaphy in pediatric patients with clinical unilateral inguinal hernia to evaluate for contralateral patent processus vaginalis (CPPV). METHODS: The data evaluated are age, sex, negative findings, positive findings, false positives, false negatives, recurrences, date of recurrence, and complications. Patients who clinically had bilateral hernias or were born prematurely were excluded. A 5-mm, 30° multichannel scope was used through the ipsilateral open hernia sac to explore the contralateral internal ring. A Fogarty catheter was used through one of the channels of the scope to probe the contralateral side in instances of questionable patent processus vaginalis. RESULTS: One thousand one patients were studied, and a total of 237 CPPVs (23%) were identified. The highest incidence of CPPV was found in those patients younger than 1 year (44%). Contralateral patent processus vaginalis was identified and ligated in 34% of patients younger than 2 years, 20% in patients 2 to 8 years old, and 17% of patients 9 to 18 years old. There were no false positives and 6 false negatives (0.6%) of the contralateral side. There were 3 (0.3%) recurrent inguinal hernias of the ipsilateral side and no complications. CONCLUSIONS: The use of a multichannel scope through the ipsilateral open hernia sac during inguinal herniorrhaphy in pediatric patients with clinical unilateral inguinal hernia to evaluate for CPPV proved to be effective, cost-effective, and safe. Our procedure eliminated any additional scars and the cost of trocars and permitted us to probe the contralateral internal ring. Unnecessary open exploration was spared in 56% of children younger than 1 year and proved to be useful in all pediatric patients up to the age of 18 years.

Pleuroperitoneal canal closure and the fetal adrenal gland.

Pleuroperitoneal canal (PP canal) closure is generally considered to result from an increase in the height, and subsequent fusion, of the bilateral pleuroperitoneal folds (PP folds). However, the folds develop in the area ventral to the adrenal, in contrast to the final position of the diaphragm, which extends to the dorsal side of the adrenal (the "retro-adrenal" diaphragm). We examined the semiserial histology of 20 human embryos and fetuses (crown-rump length 11-40 mm). We started observations of the canal at the stage through which the lung bud extends far caudally along the dorsal body wall to the level of the future adrenal, and the phrenic nerve has already reached the PP fold. Subsequently, the developing adrenal causes narrowing of the dorsocaudal parts of the canal, and provides the bilateral midsagittal recesses or "false" bottoms of the pleural cavity. However, at this stage, the PP fold mesenchymal cells are still restricted to the ventral side of the adrenal, especially along the liver and esophagus. Thereafter, in accordance with ascent of the lung, possibly due to anchoring of the liver to the adrenal, the PP fold mesenchymal cells seem to migrate laterally along the coelomic mesothelium covering some sheet-like loose mesenchymal tissue behind the adrenal. Final closure of the PP canal by lateral migration to provide the "retro-adrenal" diaphragm is a process quite different from the common dogma. It is likely that the sheet-like loose mesenchymal tissue becomes the caudal part of the pleural cavity through a process involving cell death.

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.

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.

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.