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(Hirschsprung's Disease; Congenital Megacolon)
(Also see Overview of Congenital GI Anomalies.)
Hirschsprung disease is a congenital anomaly of innervation of the lower intestine, usually limited to the colon, resulting in partial or total functional obstruction. Symptoms are obstipation and distention. Diagnosis is by barium enema and rectal biopsy. Anal manometry can help in the evaluation and reveals lack of relaxation of the internal anal sphincter. Treatment is surgical.
Hirschsprung disease is caused by congenital absence of the Meissner and Auerbach autonomic plexus (aganglionosis) in the intestinal wall. The estimated incidence is 1 in 5000 live births. Disease is usually limited to the distal colon (75% of cases) but can involve the entire colon or even the entire large and small bowels; the denervated area is always contiguous. Males are more commonly affected (male:female ratio 4:1) unless the entire colon is involved, in which case there is no gender difference.
The etiology of the aganglionosis is thought to be the failure of migration of neuroblasts from the neural crest. There is a significant genetic component to this disorder and at least 12 different genetic mutations are associated with Hirschsprung. The likelihood of disease among family members increases with increasing length of the involved gut—3 to 8% for disease of the distal colon and up to 20% for disease involving the entire colon. About 20% of patients with Hirschsprung disease have another congenital anomaly, and about 12% have a genetic abnormality (Down syndrome is the most common). About 20% of patients with congenital central hypoventilation syndrome also have Hirschsprung disease; the combination is referred to as Haddad syndrome. About 40% of patients with intestinal neuronal dysplasia (IND) have Hirschsprung disease.
Peristalsis in the involved segment is absent or abnormal, resulting in continuous smooth muscle spasm and partial or complete obstruction with accumulation of intestinal contents and massive dilation of the more proximal, normally innervated intestine. Skip lesions almost never occur.
Patients most commonly present early in life, but some do not present until childhood or even adulthood.
Normally, 98% of neonates pass meconium in the first 24 h of life. About 50 to 90% of neonates with Hirschsprung disease fail to pass meconium in the first 48 h of life. Infants present with obstipation, abdominal distention, and, finally, vomiting as in other forms of distal bowel obstruction. Occasionally, infants with ultrashort segment aganglionosis have only mild or intermittent constipation, often with intervening bouts of mild diarrhea, resulting in delay in diagnosis. In older infants and children, symptoms and signs may include anorexia, constipation, lack of a physiologic urge to defecate, and, on digital rectal examination, an empty rectum with stool palpable higher up in the colon and an explosive passage of stool upon withdrawal of the examining finger (blast sign). Infants may also fail to thrive. Less commonly, infants may present with Hirschsprung enterocolitis.
Diagnosis of Hirschsprung disease should be made as soon as possible. The longer the disease goes untreated, the greater the chance of developing Hirschsprung enterocolitis (toxic megacolon), which may be fulminant and fatal. Most patients can be diagnosed in early infancy.
Initial approach is typically with barium enema and/or rectal suction biopsy. Barium enema may show a transition in diameter between the dilated, normally innervated colon proximal to the narrowed distal segment (which lacks normal innervation). Barium enema should be done without prior preparation, which can dilate the abnormal segment, rendering the test nondiagnostic. Because characteristic findings may not be present in the neonatal period, a 24-h postevacuation x-ray should be taken; if the colon is still filled with barium, Hirschsprung disease is likely. A rectal suction biopsy can disclose the absence of ganglion cells. Acetylcholinesterase staining can be done to highlight the enlarged nerve trunks. Some centers also can do rectal manometrics, which can reveal lack of relaxation of the internal anal sphincter that is characteristic of the abnormal innervation. Definitive diagnosis requires a full-thickness biopsy of the rectum or colon to identify the full extent of the disease and thus plan surgical treatment.
Treatment of Hirschsprung disease is surgical repair by bringing normally innervated bowel to the anus with preservation of the anal sphincters. In the neonate, this procedure typically involved a colostomy proximal to the aganglionic segment to decompress the colon and allow the neonate to grow before the 2nd stage of the procedure. Later resection of the entire aganglionic portion of the colon and a pull-through procedure is done. However, a number of centers now do a 1-stage procedure in the neonatal period for short-segment disease. Results using laparoscopic technique are similar to those of the open method and are associated with shorter hospitalizations, earlier initiation of feeding, and less pain.
After definitive repair, the prognosis is good, although a number of infants have chronic dysmotility with constipation, obstructive problems, or both.
Congenital denervation affects the distal colon and less often larger regions of the colon and sometimes even the small bowel.
Infants typically present with findings of distal bowel obstruction, such as obstipation, abdominal distention, and vomiting.
Barium enema findings (done without prior preparation) and rectal manometry are highly suggestive; diagnosis is confirmed by rectal biopsy.
The affected segment is resected surgically.
Hirschsprung enterocolitis is a life-threatening complication of Hirschsprung disease resulting in a grossly enlarged colon, often followed by sepsis and shock.
The etiology of Hirschsprung enterocolitis seems to be marked proximal dilation secondary to obstruction, with thinning of the colonic wall, bacterial overgrowth, and translocation of gut bacteria. Sepsis or shock can develop (more often when the entire colon is affected by Hirschsprung), and death can follow rapidly; mortality rate is about 1%. Close monitoring of infants with Hirschsprung disease is therefore essential.
Hirschsprung enterocolitis occurs most commonly in the first several months of life before surgical correction but can occur postoperatively, typically in the first year after surgery. Infants present with fever, abdominal distention, diarrhea (which may be bloody), and, subsequently, obstipation.
Initial treatment of Hirschsprung enterocolitis is supportive with fluid resuscitation, decompression with an NGT and rectal tube, and broad-spectrum antibiotics to include anaerobic coverage (eg, a combination of ampicillin, gentamicin, and clindamycin). Some experts advocate saline enemas to clean out the colon, but this must be done carefully so as not to increase colonic pressure and cause perforation. Surgery is the definitive treatment for infants who have not yet undergone surgical repair, as well as for infants with perforation or necrotic gut.
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