[Intestinal neuronal dysplasia type B: how do we understand it today?]

Interstitial cells of Cajal: clinical relevance in pediatric gastrointestinal motility disorders

Interstitial cells of Cajal (ICCs) are pacemaker cells of gastrointestinal motility that generate and transmit electrical slow waves to smooth muscle cells in the gut wall, thus inducing phasic contractions and coordinated peristalsis. Traditionally, tyrosine-protein kinase Kit (c-kit), also known as CD117 or mast/stem cell growth factor receptor, has been used as the primary marker of ICCs in pathology specimens. More recently, the Ca2+-activated chloride channel, anoctamin-1, has been introduced as a more specific marker of ICCs. Over the years, various gastrointestinal motility disorders have been described in infants and young children in which symptoms of functional bowel obstruction arise from ICC-related neuromuscular dysfunction of the colon and rectum. The current article provides a comprehensive overview of the embryonic origin, distribution, and functions of ICCs, while also illustrating the absence or deficiency of ICCs in pediatric patients with Hirschsprung disease intestinal neuronal dysplasia, isolated hypoganglionosis, internal anal sphincter achalasia, and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome.

Advances in understanding functional variations in the Hirschsprung disease spectrum (variant Hirschsprung disease)

Hirschsprung disease (HSCR) is a fairly well understood congenital, genetically based functional obstruction due to the congenital absence of ganglion cells in the distal bowel. However, although over 90% of Hirschsprung cases conform to the normally accepted histological diagnostic criteria, it has become increasingly clear that in addition to HSCR, there is a group of functional disturbances relating to a number of other congenital neurodysplastic conditions causing some degree of gastrointestinal tract malfunction. Although these represent a variety of possibly separate conditions of the enteric nervous system, this spectrum it would appear to be also influenced by similar developmental processes. The term "variant Hirschsprung" is commonly used to describe these conditions, but ganglion cells are mostly present if abnormal in number and distribution. These conditions are a problem group being amongst the most difficult to diagnose and treat with possible practical and legal consequences. The problem appears to be possibly one of definition which has proven difficult in the relative paucity of normal values, especially when correlated to age and gestation. It is the purpose of this paper to review the current position on these conditions and to explore possible shared common pathogenetic and genetic mechanisms. This article explores those conditions where a similar pathogenetic mechanisms to HSCR can be demonstrated (e.g. hypoganglionosis) as well as other neural features, which appear to represent separate conditions possibly linked to certain syndromes.

Classification and diagnostic criteria of variants of Hirschsprung's disease

"Variants of Hirschsprung's disease" are conditions that clinically resemble Hirschsprung's disease (HD), despite the presence of ganglion cells in rectal suction biopsies. The diagnosis and management of these patients can be challenging. Specific histological, immunohistochemical and electron microscopic investigations are required to characterize this heterogeneous group of functional bowel disorders. Variants of HD include intestinal neuronal dysplasia, intestinal ganglioneuromatosis, isolated hypoganglionosis, immature ganglia, absence of the argyrophil plexus, internal anal sphincter achalasia and congenital smooth muscle cell disorders such as megacystis microcolon intestinal hypoperistalsis syndrome. This review article systematically classifies variants of HD based on current diagnostic criteria with an additional focus on pathogenesis, epidemiology, clinical presentation, management and outcome.

Variants of Hirschsprung disease

Variants of Hirschsprung disease are conditions that clinically resemble Hirschsprung disease, despite the presence of ganglion cells in rectal suction biopsies. The characterization and differentiation of various entities are mainly based on histologic, immunohistochemical, and electron microscopy findings of biopsies from patients with functional intestinal obstruction. Intestinal neuronal dysplasia is histologically characterized by hyperganglionosis, giant ganglia, and ectopic ganglion cells. In most intestinal neuronal dysplasia cases, conservative treatments such as laxatives and enema are sufficient. Some patients may require internal sphincter myectomy. Patients with the diagnosis of isolated hypoganglionosis show decreased numbers of nerve cells, decreased plexus area, as well as increased distance between ganglia in rectal biopsies, and resection of the affected segment has been the treatment of choice. The diagnosis of internal anal sphincter achalasia is based on abnormal rectal manometry findings, whereas rectal suction biopsies display presence of ganglion cells as well as normal acetylcholinesterase activity. Internal anal sphincter achalasia is either treated by internal sphincter myectomy or botulinum toxin injection. Megacystis microcolon intestinal hypoperistalsis is a rare condition, and the most severe form of functional intestinal obstruction in the newborn. Megacystis microcolon intestinal hypoperistalsis is characterized by massive abdominal distension caused by a largely dilated nonobstructed bladder, microcolon, and decreased or absent intestinal peristalsis. Although the outcome has improved in recent years, survivors have to be either maintained by total parenteral nutrition or have undergone multivisceral transplant. This review article summarizes the current knowledge of the aforementioned entities of variant HD.

[Twenty years diagnostic competence center for Hirschsprung's disease in Basel]

BACKGROUND

The experience gained by the Basel Hirschsprung Competence Center over 20 years is presented.

MATERIALS AND METHODS

A total of 19,365 rectal mucosal biopsies were investigated in the 20 years between 1987 and 2006. All biopsies of rectal mucosa originated from 6,615 children aged between 1 week and 4 years. Biopsies were collected in teaching hospitals all over Germany and transported on dry ice by Intercity Courier Service. Serial sections of frozen tissue were made using a cryostat. Enzyme histochemical staining was performed.

RESULTS

A total of 935 cases of Hirschsprung's disease (14%) were observed (769 cases of classical Hirschsprung's disease, 68 total colon aganglionosis, 98 ultrashort rectum aganglionosis). Total colon aganglionosis was found in 1.0% and the frequency of ultrashort Hirschsprung' disease was 1.4%. The quality of the histological results was confirmed by a second independent investigator. There were neither false positive nor false negative diagnoses. Enzyme histochemical staining results were readable within 2 h. Acetylcholinesterase, which is significantly increased in Hirschsprung's disease, was used for nerve fiber staining. Succinic and lactic dehydrogenases and nitric oxide synthase served as confirmatory proof of aganglionosis (elective nerve cell staining of the submucous plexus).

CONCLUSION

Among 100 children with chronic constipation an average of 12 children were diagnosed with Hirschsprung's disease. Of these 2% showed total colon aganglionosis or ultrashort Hirschsprung's disease. Enzyme histochemical diagnosis of Hirschsprung's disease proved 100% reliable and time saving.

The histopathology of gastrointestinal motility disorders in children

Gastrointestinal motility disorders and chronic constipation are common pediatric problems. Symptoms of abdominal discomfort are frequently encountered in the daily practice of pediatricians and pediatric surgeons. Normal peristalsis depends on the interaction between muscles, nerve cells, and tendinous connective tissue of muscularis propria. Malfunction of any of these components results in a motility disorder. Aganglionosis, typically of the left distal colon, is the cause of Hirschsprung disease. Hypoganglionosis constitutes another gastrointestinal motility disorder. In hypoplastic hypoganglionosis, the number of nerve cells and the size of ganglia of the enteric nervous system are reduced, resulting in symptoms similar to aganglionosis. In intestinal neuronal dysplasia type B, submucous plexus development is disturbed. Immaturity of the enteric nervous system, but also ganglioneuromatosis, can be the underlying cause of chronic constipation. Chronic constipation may be caused by a myopathy. Aplasia or atrophy of the tendinous connective tissue of muscularis propria may cause desmosis, which may result in an aperistaltic syndrome. In severe chronic constipation, a histopathological diagnosis of the underlying cause is useful. In the diagnostic approach for most of these causes of chronic constipation, enzyme histochemistry is an efficient tool to complement conventional immunohistochemical and selected molecular technologies. An interdisciplinary approach of a gastrointestinal working group is beneficial in the management of these difficult patients.

Anorectal manometry with reference to operative rectal biopsy for the diagnosis/exclusion of Hirschprung's disease in children under 1 year of age

AIMS

To establish the accuracy of anorectal manometry (ARM) with reference to operative rectal biopsy in the investigation of children under 1 year of age with defaecation difficulties.

MATERIALS AND METHODS

The records of all infants who underwent ARM and operative rectal biopsy at our centre between 1994 and 2007 were reviewed. ARM was performed by a consultant paediatric surgeon in each and under ketamine anaesthesia, as operative rectal biopsy was taken.

RESULTS

There were 81 patients (49 males, 32 females). The median age at investigation was 2 months (range 0.1-11 months). Thirty-three patients (41%) had Hirschprung's disease. No patient with a normal recto-anal inhibitory reflex (RAIR) had Hirschprung's disease (100% negative predictive value). No patient with Hirschprung's disease exhibited a reflex (100% sensitivity). The specificity and positive predictive value of ARM for Hirschprung's disease were 83% and 80%, respectively. Bowel habit normalised in 88% of patients with a reflex within 1 year.

CONCLUSIONS

In children under 1 year of age, Hirschprung's disease is very unlikely in the presence of a RAIR. The specificity and positive predictive value of ARM for the diagnosis of Hirschprung's disease are inferior to those of rectal suction biopsy, and therefore, it cannot be recommended for use as a sole diagnostic tool for this disease. ARM may be a useful investigation in patients where the histologic specimen is inadequate and/or functional constipation is the most likely diagnosis. If RAIR is present, rectal biopsy may not be required.