Hirschsprung's disease (congenital megacolon)

Hirschsprung's disease (congenital megacolon) is a congenital anomaly of the innervation of the lower intestine, usually limited to the colon, resulting in partial or complete functional intestinal obstruction. Symptoms include persistent constipation and abdominal distension. Diagnosis is by barium enema and biopsy. Treatment of Hirschsprung's disease is surgical.

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What causes Hirschsprung's disease?

Hirschsprung's disease is caused by the congenital absence of the autonomic nerve plexuses (Meissner's and Auerbach's) in the intestinal wall. The lesion is usually limited to the distal colon, but may involve the entire colon or even the entire large and small intestines. Peristalsis in the affected segment is absent or abnormal, resulting in persistent smooth muscle spasm and partial or complete intestinal obstruction with accumulation of intestinal contents and massive dilation of the proximal, normally innervated segment. Alternation between affected and unaffected segments is almost never observed.

Symptoms of Hirschsprung's disease

Most often, symptoms of Hirschsprung disease appear early: within the first month in 15% of patients, by one year in 60%, and by 4 years of age in 85%. In infants, manifestations include chronic constipation, abdominal distension, and eventually vomiting as in other forms of low bowel obstruction. Occasionally, children with a very short zone of aganglionosis have only mild or recurrent constipation, often alternating with episodes of mild diarrhea, leading to a delay in diagnosis. In older children, manifestations may include anorexia, lack of psychological urge to defecate, and an empty rectum with palpable stool above the site of obstruction on examination. The child may also be undernourished.

Hirschsprung's enterocolitis

Hirschsprung's enterocolitis (toxic megacolon) is a life-threatening complication of Hirschsprung's disease that leads to severe dilation of the colon, often followed by sepsis and shock.

The cause of Hirschsprung's enterocolitis is associated with severe dilation of the proximal segment due to intestinal obstruction, thinning of the intestinal wall, bacterial overgrowth, and migration of intestinal microorganisms. Shock can develop rapidly, followed by death. Therefore, regular frequent examinations of children with Hirschsprung's disease are necessary.

Hirschsprung's enterocolitis most often develops in the first months of life before surgical correction, but can also occur after surgery. Clinical manifestations include fever, abdominal distension, diarrhea (which may be bloody), and later persistent constipation.

Initial treatment is supportive, with fluid replacement, bowel decompression via nasogastric and rectal tubes, and broad-spectrum antibiotics including anaerobes (eg, a combination of ampicillin, gentamicin, and clindamycin). Some experts suggest saline enemas to cleanse the bowel, but these should be given carefully to avoid increasing colonic pressure and causing perforation. As noted above, definitive treatment is surgical.

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Diagnosis of Hirschsprung's disease

Hirschsprung's disease should be diagnosed as early as possible. The longer the disease is left untreated, the higher the risk of developing Hirschsprung's enterocolitis (toxic megacolon), which can be fulminant and lead to the child's death. Most cases can be diagnosed in the first months of life.

Initial management includes barium enemas or sometimes rectal biopsy. Barium enema may show a difference in diameter between the dilated, proximal, normally innervated segment and the narrowed distal segment (aganglionic zone). Barium enema should be performed without prior preparation, which may dilate the affected segment, making the examination nondiagnostic. Because characteristic features may be absent in the neonatal period, a delayed film should be obtained at 24 hours; if the colon remains barium-filled, the diagnosis of Hirschsprung disease is likely. Rectal biopsy may show absence of ganglion cells. Acetylcholinesterase staining may be done to demonstrate robust nerve trunks. Some centers also have the capability of performing rectoscopy, which may show abnormal innervation. Definitive diagnosis requires full-thickness rectal biopsy.

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Treatment of Hirschsprung's disease

Treatment of Hirschsprung disease in the neonatal period has typically involved a colostomy above the aganglion to decompress the colon and allow the baby to grow before the second stage of surgery. Later, the entire aganglion is resected and the colon pulled down. However, some centers now perform a single-stage operation in the neonatal period.

After final correction, the prognosis is good, although some children experience chronic motility disorders with constipation and/or symptoms of obstruction.