HIRSCHSPRUNG DISEASE BOWEL OBSTRUCTION

Hirschsprung disease : Hirschsprung disease is a disorder of the neuroenteric pathways within the distal large bowel that prevents bowel relaxation, resulting in a functional distal bowel obstruction. Hirschsprung disease is not an acquired disease as the name suggests, but rather is a congenital absence of neuroganglion cells from the distal intestine that affects 1 in 4500-7000 newborns. Hirschsprung disease is more common in white infants and affects males 4 times more frequently than females. In approximately 12.5% of patients, Hirschsprung disease may be familial, especially when the entire colon is affected, which is termed total colonic aganglionosis.

Functional bowel obstruction in Hirschsprung disease results from an inability of the colon to relax during peristalsis. The relaxation phase of peristalsis usually occurs as a reflex to the antegrade peristaltic wave. In Hirschsprung disease, the affected bowel cannot relax and, therefore, remains contracted. The relaxation phase reflex is controlled by neuroenteric ganglion cells, which are present in the submucosa layer of the intestine. Normally, at 7-12 weeks' development, neuroenteric ganglion cells migrate from the neural crest along the bowel distally to reach the distal rectum. If these ganglion cells are not present, the peristaltic relaxation phase is not conducted to the affected distal segment of the bowel.

The affected distal colon does not relax appropriately, and a functional obstruction develops. Because of the migration pattern of these ganglion cells, Hirschsprung disease usually affects a continuous segment of bowel extending from the rectum proximally to the level of normal ganglionated bowel. The extent of the aganglionic segment varies with each patient. The genetic defect responsible for Hirschsprung disease has been linked to the ret protooncogene, located on the long arm of chromosome 10. Current understanding of the influence of the ret protooncogene on migration of the ganglion cells is evolving. Hirschsprung disease may also be linked to other disorders of bowel motility.

Diagnosis of Hirschsprung disease is suggested by contrast enema and confirmed by rectal biopsy. If Hirschsprung disease is suggested, perform a contrast enema. Older children with Hirschsprung disease show a characteristic transition zone between narrow-caliber aganglionic bowel and dilated upstream normally ganglionated bowel. A distinct transition zone is often difficult to observe in newborns. Failure to evacuate the contrast in 24 hours following the contrast enema may be diagnostic for Hirschsprung disease. Anal manometry may also suggest a diagnosis of Hirschsprung disease but is difficult to perform in the newborn period.

The criterion standard to confirm Hirschsprung disease is rectal biopsy. Rectal biopsy may be readily performed at the bedside in newborns with a specially designed rectal biopsy tool. This instrument suctions the rectal mucosa and submucosa into the tool and amputates the specimen without perforating the serosa of the rectum. Collection of the specimen via suction is replacing the more conventional open biopsy method of obtaining tissue for histopathologic examination. The specimen is examined for the presence of ganglion cells in the submucosal layer. In addition, acetylcholinesterase staining of the submucosa identifies abnormal hypertrophic nerve fibers in Hirschsprung tissue.

All children with delayed passage of meconium with a suspicious finding on contrast enema should undergo rectal biopsy prior to discharge. Constipation of varying severity is a feature of all patients with Hirschsprung disease. The length of the aganglionic segment greatly influences bowel dysmotility. Aganglionosis confined to a short segment of distal rectum may cause only mild constipation, while patients with longer segments of aganglionic bowel may present with complete functional obstruction in the newborn period. Infants with Hirschsprung disease frequently present with enterocolitis.

A child may exhibit explosive diarrhea, sepsis, and abdominal distention. The mucosal integrity of the massively dilated proximal bowel may be compromised, allowing bacterial invasion of the epithelium. Management of Hirschsprung enterocolitis includes aggressive washout of the distal segment to decompress the bowel. Intravenous antibiotics are administered. A diverting colostomy has been traditionally performed to aid with this process.

Treatment of Hirschsprung disease is surgical. Several different surgical approaches have been described that pull ganglionated bowel down to the rectum. Most pediatric surgeons have performed a colostomy to allow for decompression of the bowel. Most recently, a minimally invasive pull-through technique with a transanal approach but without formal laparotomy has gained acceptance.

For many surgeons, newer laparoscopic techniques greatly facilitate performance of the transanal approach. This primary pull-through technique avoids both a formal laparotomy and a diverting ostomy and may be appropriate for newborns with Hirschsprung disease who have no evidence of enterocolitis. Long-term complications of Hirschsprung disease include a continued risk for chronic constipation and enterocolitis, even after successful pull-through. Bowel dysmotility may persist in many patients despite successful removal of aganglionic bowel.

Outcome for patients with Hirschsprung disease who have undergone a pull-through procedure is generally good in terms of both continence and stool frequency.