Hypothesis: pathogenesis of skip areas in long-segment Hirschsprung's disease

Skip segment Hirschsprung's disease: report of two rare cases and management

PURPOSE

Skip segment Hirschsprung's disease (SS-HSCR) is defined as the occurrence of a segment of ganglionated intestine surrounded proximally and distally by aganglionosis. The presence of the skip intestinal segment often leads to clinical misdiagnosis, missed diagnosis or inadequate resection of the lesions. The purpose was to describe two new cases of SS-HSCR with the aim of proposing questions regarding the diagnosis and treatment of this rare disease.

METHODS

We reported two cases of infants with SS-HSCR that were admitted to our institution within the last 3 years.

RESULTS

One patient had a skip segment of ganglionated intestine in the ascending colon. In the other patient, there were no ganglionic cells in the rectum and appendix, but ganglionic cells were visible in the proximal ascending colon. The entire colons in the both cases were finally resected, and a pull-through operation was performed.

CONCLUSION

Multipoint biopsy should be performed when the biopsy results are inconsistent with clinical manifestations. Intraoperative laparoscopic identification of the transition zone may be necessary when TCA is suspected. Multisegment biopsy is needed to as a preventative measure for SS-HSCR if TCA is indicated during surgery. Further study is required to determine the optimal length and method of retention of segments.

Skip segment Hirschsprung's disease: diagnostic clues and surgical management

It is challenging to establish a definitive diagnosis and initiate timely management for skip segment Hirschsprung's disease (SSHD). Herein, we report three cases of SSHD at our institution between December 2008 and March 2018. Patient #1 was misdiagnosed and underwent three successive operations within 2 years. Patient #2 and #3 were diagnosed timely based on previous experience. A segmental narrowing detected by barium enema may raise the possibility of SSHD. Laparoscopic-guided multipoint biopsy is regarded as a mini-invasive and purposeful way to take representative samples after locating the segmental narrowing intraoperatively and accurate the final diagnosis. The laparoscopic-assisted pull-through procedure with radical resection from the distal rectum to the most proximal margin of the diseased skip segment is safe and effective in treating patients with SSHD.Level of evidence: Level III.

Case report of a skip segment Hirschsprung's disease: A real phenomenon

INTRODUCTION AND IMPORTANCE

Hirschsprung's disease is a congenital anomaly that results from an incomplete craniocaudal migration and maturation of intestinal ganglion progenitor cells leading to distal intestinal aganglionosis. Skip segment Hirschsprung's disease is an extremely rare phenomenon. We report a case involving only the small bowel with confirmed colonic ganglionosis.

CASE PRESENTATION

A case report of a 14-month-old with a skipped segment involving the distal 50 cm of the small bowel associated with colonic ganglionosis is presented. A current review of the literature is discussed.

CLINICAL DISCUSSION

Our patient had persistent obstructive symptoms despite undergoing a technically good, ganglionic pull-through operation at an outside institution. A laparoscopic-assisted pull-through might have documented a small bowel wall diameter discrepancy.

CONCLUSION

Although rare, skip segment Hirschsprung's disease is a real phenomenon that paediatric surgeons should be aware of and could involve small and large bowels.

Mesenteric Neural Crest Cells Are the Embryological Basis of Skip Segment Hirschsprung's Disease

BACKGROUND & AIMS

Defective rostrocaudal colonization of the gut by vagal neural crest cells (vNCCs) results in Hirschsprung's disease (HSCR), which is characterized by aganglionosis in variable lengths of the distal bowel. Skip segment Hirschsprung's disease (SSHD), referring to a ganglionated segment within an otherwise aganglionic intestine, contradicts HSCR pathogenesis and underscores a significant gap in our understanding of the development of the enteric nervous system. Here, we aimed to identify the embryonic origin of the ganglionic segments in SSHD.

METHODS

Intestinal biopsy specimens from HSCR patients were prepared via the Swiss-roll technique to search for SSHD cases. NCC migration from the neural tube to the gut was spatiotemporally traced using targeted cell lineages and gene manipulation in mice.

RESULTS

After invading the mesentery surrounding the foregut, vNCCs separated into 2 populations: mesenteric NCCs (mNCCs) proceeded to migrate along the mesentery, whereas enteric NCCs invaded the foregut to migrate along the gut. mNCCs not only produced neurons and glia within the gut mesentery, but also continuously complemented the enteric NCC pool. Two new cases of SSHD were identified from 183 HSCR patients, and Ednrb-mutant mice, but not Ret^-/- mice, showed a high incidence rate of SSHD-like phenotypes.

CONCLUSIONS

mNCCs, a subset of vNCCs that migrate into the gut via the gut mesentery to give rise to enteric neurons, could provide an embryologic explanation for SSHD. These findings lead to novel insights into the development of the enteric nervous system and the etiology of HSCR.

Advances and Pitfalls in the Diagnosis of Hirschsprung Disease

Surgical pathology for Hirschsprung disease (HSCR) occasionally is difficult, especially for those who encounter the disorder infrequently. This article reviews pathologic features of HSCR, considers various specimens the pathologist is required to evaluate, and discusses useful ancillary tests. Potential diagnostic pitfalls are highlighted, and helpful hints are provided to successfully navigate challenging situations. Finally, the article looks forward to new ancillary tests on the horizon and future topics for HSCR research.

Postoperative Pullthrough Obstruction in Hirschsprung Disease: Etiologies and Diagnosis

Some patients continue to have obstructive symptoms and/or incontinence after pullthrough surgery for Hirschsprung disease. Incontinence can be due to injury to the anal sphincter and/or dentate line, abnormal colonic motility (nonretentive), or a chronic large stool burden (retentive). A diagnostic algorithm based on clinical and pathological evaluations can be applied to distinguish potential etiologies for obstructive symptoms, which segregate into anatomic (mechanical or histopathological) or physiologic subgroups. Valuable clinical information may be obtained by anorectal examination under anesthesia, radiographic studies, and anorectal or colonic manometry. In addition, histopathological review of a patient's original resection specimen(s) as well as postoperative biopsies of the neorectum usually are an important component of the diagnostic workup. Goals for the surgical pathologist are to exclude incomplete resection of the aganglionic segment or transition zone and to identify other neuromuscular pathology that might explain the patient's dysmotility. Diagnoses established from a combination of clinical and pathological data dramatically alter management strategies. In rare instances, reoperative pullthrough surgery is required, in which case the pathologist must be aware of histopathological features specific to redo pullthrough resection specimens.

Distal Rectal Skip-Segment Hirschsprung Disease and the Potential for False-Negative Diagnosis

In skip-segment Hirschsprung disease (SS-HSCR), an aganglionic segment of bowel, which extends proximally from the distal rectum, is interrupted by a ganglionated "skip segment." Skip segments are usually located far proximal to the rectum where they do not interfere with initial diagnosis, although the possibility of distal SS-HSCR should be considered during interpretation of intraoperative biopsies or patients with atypical postoperative courses. We report 2 cases of SS-HSCR with skip areas in the distal rectum, 1 of which led to a false-negative diagnosis by suction rectal biopsy. These 2 cases of SS-HSCR, along with others in the literature, highlight the point that ganglionic skip segments can confuse clinicians and lead to inadequate bowel resection, diagnostic delay, or a false-negative diagnosis. The pathogenesis of SS-HSCR is discussed in light of recent discoveries regarding transmesenteric migration of vagal neural crest cells and the role of sacral neural crest cells in hindgut neurodevelopment.

The neural crest: a versatile organ system

The neural crest is the name given to the strip of cells at the junction between neural and epidermal ectoderm in neurula-stage vertebrate embryos, which is later brought to the dorsal neural tube as the neural folds elevate. The neural crest is a heterogeneous and multipotent progenitor cell population whose cells undergo EMT then extensively and accurately migrate throughout the embryo. Neural crest cells contribute to nearly every organ system in the body, with derivatives of neuronal, glial, neuroendocrine, pigment, and also mesodermal lineages. This breadth of developmental capacity has led to the neural crest being termed the fourth germ layer. The neural crest has occupied a prominent place in developmental biology, due to its exaggerated migratory morphogenesis and its remarkably wide developmental potential. As such, neural crest cells have become an attractive model for developmental biologists for studying these processes. Problems in neural crest development cause a number of human syndromes and birth defects known collectively as neurocristopathies; these include Treacher Collins syndrome, Hirschsprung disease, and 22q11.2 deletion syndromes. Tumors in the neural crest lineage are also of clinical importance, including the aggressive melanoma and neuroblastoma types. These clinical aspects have drawn attention to the selection or creation of neural crest progenitor cells, particularly of human origin, for studying pathologies of the neural crest at the cellular level, and also for possible cell therapeutics. The versatility of the neural crest lends itself to interlinked research, spanning basic developmental biology, birth defect research, oncology, and stem/progenitor cell biology and therapy.

A rare case of multiple skip segment Hirschsprung's disease in the ileum and colon

As a rare form of Hirschsprung's disease, skip segment Hirschsprung's disease (SSHD) involves a "skip area" in normally ganglionated intestine, surrounded by aganglionosis. We report a case of multiple SSHD in the ileum and colon with total colonic aganglionosis. To our knowledge, this is the 27th case of SSHD, the third paper on multiple-segment SSHD, and the second patient with SSHD in the ileum to be reported in the English literature.

Skip segment Hirschsprung's disease: a case report and novel management technique

Skip segment Hirschsprung's disease is a condition where an area of normally ganglionated intestine is interspersed proximally and distally by aganglionic segments. The occurrence of skip segment has no clear embryological explanation, contrary to the present concept of failure of cranio-caudal migration of neural crest-derived cells in Hirschsprung's disease. Only 25 case reports have been published in literature so far and this is possibly the first to be reported from Asia. We report one such case with novel surgical management.

Histopathologic delineation of the transition zone in short-segment Hirschsprung disease

Failure to completely resect the transition zone (TZ) between aganglionic and neuroanatomically normal bowel ("TZ pull-through") is considered one reason for postoperative obstructive symptoms in Hirschsprung disease (HD). Despite years of study, the proximal boundary of the TZ remains nebulous, complicated by discordant, often subjective, histopathologic definitions. In order to objectively delineate the TZ, transverse sections at 1 cm intervals from the rectums of 9 non-HD autopsy subjects and resections from 15 infants with short-segment HD were immunostained with Hu (ganglion cell bodies) and glucose transporter 1 (Glut1) (perineurium of extrinsic nerves), and 6 putative features of TZ were examined: (1) aganglionosis of ≥1/8th circumference; (2) myenteric or submucosal hypoganglionosis; (3) hypertrophic submucosal nerves; (4) Glut1+ submucosal innervation; (5) submucosal hyperganglionosis; and (6) "ectopic" ganglia in lamina propria, muscularis propria, or serosa. In non-HD controls, Glut1+ submucosal innervation, hypertrophic nerves, partial circumferential aganglionosis, and hypoganglionosis were absent or restricted to the distal 2 cm. In contrast, all 6 neuropathologic features of TZ were identified proximal to the aganglionic segment in the majority of HD resections, but the length of the TZ ranged from 0 to 12 cm, depending on which neuropathologic feature was considered. Excluding submucosal hyperganglionosis and ectopic ganglia, the TZ was generally ≤5 cm. Many features of TZ cannot be excluded intraoperatively with a biopsy or a full-circumference frozen section. However, partial circumferential aganglionosis, severe myenteric hypoganglionosis, and hypertrophic submucosal nerves can, and probably should, be assessed in full-circumference frozen sections of the proximal resection margin, to reduce the likelihood of TZ pull-through.

Segmental aganglionosis (zonal aganglionosis or "skip" lesions) in Hirschsprungs disease: a report of 2 unusual cases

INTRODUCTION

There is accumulating evidence that "skip" lesions or zonal aganglionosis do occur in HSCR disease, albeit rarely. They are of interest because it may cause confusion in interpreting surgical margins as well as understanding the pathophysiology of HSCR disease. Normally described as "a skip area" of normally ganglionated bowel, surrounded proximally and distally by aganglionosis with variations may occur.

CASE REPORTS

We report two cases of infants with unusual types of "skip lesions", identified within the last 5 years.

RESULTS

One patient had an area of zonal aganglionosis in the transverse colon and recto-sigmoid, bordered by areas of normally enervated bowel in the right and descending colon. In the second patient, the terminal ileum, transverse, descending and sigmoid colons and rectum were histologically aganglionic, but focal patches of ganglion cells were identified in 21 cm of the right ascending colon and the appendix, suggesting some ENS plasticity and possible incomplete apoptosis.

CONCLUSION

These cases illustrate the point that the presence of ganglion cells at the resection line is not sufficient to guarantee postoperative function and "skip" lesions may uncommonly confuse the picture. In addition, they raise questions as to its pathophysiology and favor an alternate hypothesis of local changes promoting neuroblast apoptosis as the possible cause.

Trans-mesenteric neural crest cells are the principal source of the colonic enteric nervous system

Cell migration is fundamental to organogenesis. During development, the enteric neural crest cells (ENCCs) that give rise to the enteric nervous system (ENS) migrate and colonize the entire length of the gut, which undergoes substantial growth and morphological rearrangement. How ENCCs adapt to such changes during migration, however, is not fully understood. Using time-lapse imaging analyses of mouse ENCCs, we show that a population of ENCCs crosses from the midgut to the hindgut via the mesentery during a developmental time period in which these gut regions are transiently juxtaposed, and that such 'trans-mesenteric' ENCCs constitute a large part of the hindgut ENS. This migratory process requires GDNF signaling, and evidence suggests that impaired trans-mesenteric migration of ENCCs may underlie the pathogenesis of Hirschsprung disease (intestinal aganglionosis). The discovery of this trans-mesenteric ENCC population provides a basis for improving our understanding of ENS development and pathogenesis.

Small bowel skip segment Hirschprung's disease presenting with perforated Meckel's diverticulum

Skip segment Hirschprung's disease (SSHD) is an uncommon variant of Hirschprung's disease where normal intestine is interspersed proximally and distally by abnormal, aganglionated intestine. These segmental changes have no well-defined embryological explanation. We present a case of SSHD in the small bowel and concomitant perforated Meckel's diverticulum, with review of the literature relevant to SSHD.

Total colonic aganglionosis with skip lesions: report of a rare case and management

We present an unusual case of total colonic aganglionosis with well-documented skip lesions and discuss our staged approach for diagnosis and surgical management. To date, there have been few reported cases of total colonic aganglionosis with skip areas. This type of presentation challenges the accepted theory regarding the etiology of colonic aganglionosis. Although skip lesions in Hirschsprung disease are extremely rare, their existence must be appreciated especially when a patient's clinical and pathologic findings do not support classic Hirschsprung disease. If not considered, additional areas of aganglionosis can be missed at initial presentation, leading to a delay in definitive treatment. This case illustrates how careful mapping of bowel via multiple biopsies can identify and thereby preserve intervening segments of bowel with normal ganglions cells to yield the maximal amount of bowel possible.

'Hop the skip' with extended segment intestinal biopsy in Hirschsprung's disease

INTRODUCTION

Skip segment Hirschsprung's is an extremely rare condition, with only 25 reported cases in the English language literature. Diagnosis of skip segment Hirschsprung's may be missed as it is rarely suspected at initial surgery.

PRESENTATION OF CASE

A case report of an infant with total colonic aganglionosis and a skip segment Hirschsprung's in the cecum is presented. A review of literature on current surgical practice is presented along with our suggested modification to the diagnostic and therapeutic algorithm of this rare condition.

DISCUSSION

In our patient the initial leveling colostomy was incorrectly sited at the level of the first detected ganglionated segment. Subsequent recurrent episodes of enterocolitis led to a diagnosis of a long skip segment involving the ascending colon, cecum and terminal ileum. Correct leveling colostomy and a subsequent Duhamel procedure led to a good outcome.

CONCLUSION

Determination of the transition zone in Hirschsprung's may be incorrect if intestinal biopsies are terminated at the first evidence of ganglion cells. Extended segment intestinal biopsies should be included in the algorithm for management of long segment Hirschsprung's disease and will enable the surgeon to correctly detect rare manifestations such as skip segment disease at the initial procedure.

L1cam acts as a modifier gene for members of the endothelin signalling pathway during enteric nervous system development

BACKGROUND

The enteric nervous system originates from neural crest cells that migrate into the embryonic foregut and then sequentially colonize the midgut and hindgut. Defects in neural crest migration result in regions of the gut that lack enteric ganglia, a condition in humans called Hirschsprung's disease. The high degree of phenotypic variability reported in Hirschsprung's disease suggests the involvement of modifier genes.

METHODS

We used a two-locus complementation approach to screen for genetic interactions between L1cam and members of the endothelin signalling pathway. Immunohistochemistry was used to label PGP9.5(+) enteric neurons and Sox10(+) neural crest-derived cells in wholemount preparations of embryonic gut. Key Results  Loss or haploinsufficiency of L1cam significantly increased the severity of aganglionosis in Et-3 and Ednrb null mutant embryos. Furthermore, the colonization of the developing gut by neural crest-derived cells was significantly delayed in L1cam(-/y) ; Et-3(-/-) and L1cam(-/y) ;Ednrb(sl/sl) embryos.

CONCLUSIONS & INFERENCES

We have identified the X-linked gene, L1cam, as the first modifier gene for members of the endothelin signalling pathway during development of the enteric nervous system. Mutations in L1CAM may act to modulate the severity of aganglionosis in some cases of Hirschsprung's disease.

Skip segment Hirschsprung's disease: a rare phenomenon

Skip segment Hirschsprung's disease (SSHD) involves a skip area of normally ganglionated intestine, surrounded proximally and distally by aganglionosis. We report a case of SSHD in infant with total colonic aganglionosis (TCA). Although SSHD is a rare and controversial condition, it should be considered a definite entity in the evaluation of Hirschsprung's disease.

Skip segment Hirschsprung's disease: a systematic review

PURPOSE

Hirschsprung's disease is characterised by the congenital absence of ganglion cells beginning in the distal rectum and extending proximally for varying distances. 'Zonal aganglionosis' is a phenomenon involving a zone of aganglionosis occurring within normally innervated intestine. 'Skip segment' Hirschsprung's disease (SSHD) involves a 'skip area' of normally ganglionated intestine, surrounded proximally and distally by aganglionosis. While Hirschsprung's disease is believed to be the result of incomplete craniocaudal migration of neural crest-derived cells, the occurrence of SSHD has no clear embryological explanation. The aim of this study was to perform a systematic review of SSHD, reported in the literature between 1954 and 2009, in order to determine the clinical characteristics of this rare entity and its significance.

METHODS

The first reported case of SSHD was published in 1954. A systematic review of SSHD cases in the literature, from 1954 to 2009, was carried out using the electronic database 'Pubmed'. Detailed information was recorded regarding the age, gender, presenting symptoms and location of the skip segment in each patient.

RESULTS

24 cases of SSHD have been reported in the literature to date. 18/24 (75%) of these cases were males and 6/24 (25%) were females. Of these, 22/24 (92%) were cases of total colonic aganglionosis (TCA), and 2/24 (8%) were rectosigmoid Hirschsprung's disease. Of the 22 TCA cases, 9 (41%) had a skip segment in the transverse colon, 6 (27%) in the ascending colon, 2 (9%) in the caecum and 5 (23%) had multiple skip segments. In both rectosigmoid Hirschsprung's disease cases, the skip segment was in the sigmoid colon. Overall, the length of the skip segment was variable, with the entire transverse colon ganglionated in some cases.

CONCLUSION

SSHD occurs predominantly in patients with TCA. The existence of a skip area of normally innervated colon in TCA may influence surgical management, enabling surgeons to preserve and use the ganglionated skip area during pull-through operations.

Pathology of Intestinal Motor Disorders in Children

Varied intestinal neuromuscular pathologies are responsible for Hirschsprung disease and other forms of chronic pseudo-obstruction that are encountered in pediatrics. Pathologically distinct subtypes discussed in this review include aganglionosis, hypoganglionosis, neuronal intranuclear inclusion disease, ganglionitis, degenerative neuropathy, diffuse ganglioneuromatosis, neuronal dysplasia, malformations of the muscularis propria, degenerative leiomyopathy, leiomyositis, and mitochondriopathies. Emphasis is given to the histopathologic features that distinguish these conditions and their differential diagnoses.

Practical pathology and genetics of Hirschsprung's disease

Diagnosis and management of Hirschsprung's disease (HSCR) requires understanding of the malformation's anatomic features and multigenic nature. Rectal biopsies, intraoperative frozen sections, and resection specimens provide invaluable information. Extraction of these data requires thoughtful biopsy technique, adequate histologic sections, histochemistry, and collaboration of surgeon and pathologist. Critical consideration of transition zone anatomy and published studies of "transition zone pull through" indicate that more research is needed to determine how much ganglionic bowel should be resected from HSCR patients. Many HSCR-susceptibility genes have been identified, but mutational analysis has limited practical value unless family history or clinical findings suggest syndromic HSCR.

Terminal ileal atresia, total colonic aganglionosis, and thrombophilia

Inherited thrombophilia, a predisposition for a hypercoagulable state, has been associated with cases of intestinal atresia. In this communication, we report a case of terminal ileal atresia and total colonic aganglionosis (Hirschsprung's disease), a rarely documented association, in a neonate who seemed to have a hypercoagulable state. The case stresses the need for recognition of this sequence of events in order to achieve optimal management.

Gastrointestinal neuromuscular pathology: guidelines for histological techniques and reporting on behalf of the Gastro 2009 International Working Group

The term gastrointestinal neuromuscular disease describes a clinically heterogeneous group of disorders of children and adults in which symptoms are presumed or proven to arise as a result of neuromuscular, including interstitial cell of Cajal, dysfunction. Such disorders commonly have impaired motor activity, i.e. slowed or obstructed transit with radiological evidence of transient or persistent visceral dilatation. Whilst sensorimotor abnormalities have been demonstrated by a variety of methods in these conditions, standards for histopathological reporting remain relatively neglected. Significant differences in methodologies and expertise continue to confound the reliable delineation of normality and specificity of particular pathological changes for disease. Such issues require urgent clarification to standardize acquisition and handling of tissue specimens, interpretation of findings and make informed decisions on risk-benefit of full-thickness tissue biopsy of bowel or other diagnostic procedures. Such information will also allow increased certainty of diagnosis, facilitating factual discussion between patients and caregivers, as well as giving prognostic and therapeutic information. The following report, produced by an international working group, using established consensus methodology, presents proposed guidelines on histological techniques and reporting for adult and paediatric gastrointestinal neuromuscular pathology. The report addresses the main areas of histopathological practice as confronted by the pathologist, including suction rectal biopsy and full-thickness tissue obtained with diagnostic or therapeutic intent. For each, indications, safe acquisition of tissue, histological techniques, reporting and referral recommendations are presented.

Clinicopathological features in 102 cases of Hirschsprung disease

BACKGROUND

Hirschsprung disease [HD] is a predominantly childhood disorder of intestinal motility with a multifactorial and polygenic etiology. The objective of this study was to document the clinical and pathological features of HD in Kuwait, which has an estimated consanguinity rate of 54%.

METHODS

We analyzed all rectal and colonic biopsies (n=268) for suspected HD identified from the records in the Pathology Department of Al-Sabah Hospital for the period between 1994 and 2004.

RESULTS

One hundred and two patients (87 males and 15 females) had histologically confirmed HD. Fifty-eight (57%) were neonates (<1 month of age), while 21% were more than 4 months old. The diagnosis was based on open biopsy in 11 cases and rectal biopsies in 91 cases. Nine patients with open biopsies presented as intestinal obstruction, necrotizing enterocolitis, or perforation. The extent of the disease was unknown in 13 patients. There were 67 males and 3 females with short segment HD. Nine had long segment, two ultra-short segment and eight total colonic aganglionosis (TCA). Five TCA cases involved the small intestine. A skip area was observed in two cases. Six patients had other anomalies. A positive family history for HD was established in three patients. Two of these were male siblings from a consanguineous marriage and had Waardenburg syndrome.

CONCLUSION

This study has highlighted an exceptionally strong male predominance of short segment and a relatively high frequency (5.6%) of small intestinal involvement in HD in Kuwait. These data call for a more detailed epidemiological study with special emphasis on genetics.

[Hirschsprung's disease: practical considerations]

Hirschsprung's disease (1/5000 live births) is defined by the congenital absence of neuronal cells in the nervous plexuses in the distal part of the digestive tract. The disease affects the rectum and sigmoid colon in 80% of cases, or is more extensive. Hirschsprung's disease is suspected in cases of low gastrointestinal obstruction in the neonatal period, or in cases of chronic severe constipation in childhood. It is diagnosed by pathological examination of rectal biopsies that include the submucosa. After standard staining, multiple sections are scrutinized for neuronal cells. Acetylcholinesterase staining is performed on a frozen fragment to demonstrate the hyperplasia of cholinergic fibers that is very suggestive of Hirschsprung's disease. This hyperplasia decreases from the rectum to the splenic flexure of the colon. Hyperplasia of extrinsic nerve fibers and rarefaction of neuromuscular junctions in Hirschsprung's disease may be demonstrated immunohistochemically. Differential diagnosis includes chronic intestinal pseudo-obstructions. The treatment for Hirschsprung's disease is, most often, anastomosis of the normally innervated gut to the anal canal. Peri- or pre-operative biopsies assist surgery, but their interpretation is difficult in the transitional zone. The examination of the surgical specimen allows measurement of the aganglionic segment and transitional zone. Different genes (RET, most often) may be involved in sporadic or familial Hirschsprung's disease. Hirschsprung's disease is associated with other digestive or extra-digestive abnormalities in 5 to 30% of patients. Associated abnormalities may delay the diagnosis and treatment of Hirschsprung's disease.

Hirschsprung disease and other enteric dysganglionoses

Hirschsprung disease has become a paradigm for multigene disorders because the same basic phenotype is associated with mutations in at least seven distinct genes. As such, the condition poses distinct challenges for clinicians, patients, diagnostic pathologists, and basic scientists, who must cope with the implications of this genetic complexity to comprehend the pathogenesis of the disorder and effectively manage patients. This review focuses on the anatomic pathology, genetics, and pathogenesis of Hirschsprung disease and related conditions. The nature and functions of "Hirschsprung disease genes" are examined in detail and emphasis is placed on the importance of animal models to this field. Where possible, potential uses and limitations of new data concerning molecular genetics and pathogenesis are discussed as they relate to contemporary medical practices.