Atlas of pathophysiology, 2 Edition

Part II - Disorders

Gastrointestinal Disorders

Hirschsprung's Disease

Hirschsprung's disease, also called congenital megacolon or congenital aganglionic megacolon, is a congenital disorder of the large intestine, characterized by absence or marked reduction of parasympathetic ganglion cells in the colorectal wall. Hirschsprung's disease appears to be a familial, congenital defect, occurring in 1 in 5,000 to 1 in 8,000 live births. It's up to 7 times more common in males than in females (although the aganglionic segment is usually shorter in males) and is most prevalent in whites. Total aganglionosis affects both sexes equally. Females with Hirschsprung's disease are at higher risk for having affected children. This disease usually coexists with other congenital anomalies, particularly trisomy 21 and anomalies of the urinary tract such as megaloureter.

Clinical Tip

Without prompt treatment, an infant with colonic obstruction may die within 24 hours from enterocolitis that leads to severe diarrhea and hypovolemic shock. With prompt treatment, prognosis is good.

Causes

Familial congenital defect

Pathophysiology

In Hirschsprung's disease, parasympathetic ganglion cells in the colorectal wall are absent or markedly reduced in number. The aganglionic bowel segment contracts without the reciprocal relaxation needed to propel feces forward. Impaired intestinal motility causes severe, intractable constipation. Colonic obstruction can ensue, dilating the bowel and occluding surrounding blood and lymphatic vessels. The ensuing mucosal edema, ischemia, and infarction draw large amounts of fluid into the bowel, causing copious amounts of liquid stool. Continued infarction and destruction of the mucosa lead to infection and sepsis.

Signs and symptoms

In neonates

·   Failure to pass meconium within 24 to 48 hours

·   Bile-stained or fecal vomitus

·   Constipation, overflow diarrhea

·   Abdominal distention

·   Dehydration, feeding difficulties, and failure to thrive

In children

·   Intractable constipation

·   Large protuberant abdomen, easily palpated fecal masses

·   Wasted extremities (in severe cases)

·   Loss of subcutaneous tissue (in severe cases)

In adults (rare)

·   Abdominal distention

·   Chronic intermittent constipation

Complications of Hirschsprung's disease include bowel perforation, electrolyte imbalances, nutritional deficiencies, enterocolitis, hypovolemic shock, and sepsis.

Diagnostic test results

·   Rectal biopsy confirms diagnosis by showing the absence of ganglion cells.

·   Barium enema, used in older infants, reveals a narrowed segment of distal colon with a saw-toothed appearance and a funnel-shaped segment above it. This confirms the diagnosis and assesses the extent of intestinal involvement.

·   Rectal manometry detects failure of the internal anal sphincter to relax and contract.

·   Upright plain abdominal X-rays show marked colonic distention.

Treatment

·   Daily colonic lavage prior to surgery

·   Temporary colostomy or ileostomy

·   Corrective surgery

·   Antibiotics

P.189

BOWEL DILATION IN HIRSCHSPRUNG's DISEASE

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