Congenital aganglionic megacolon

Congenital aganglionic megacolon (congenital megacolon) is a congenital anomaly that is caused by a congenital absence of autonomic parasympathetic ganglion cells in the submucosal and intermuscular neural plexuses of the wall of the intestine.

Congenital aganglionic megacolon is also known as Hirschsprung disease. It is the most frequent cause of intestinal obstruction of the colon. Although it is the cause of about one-third of all obstructions in newborns, the diagnosis may not be made until later in infancy or childhood. It occurs more frequently in males than in females.

Mechanical obstruction results because of inadequate motility in an intestinal segment. The disease may be a familial congenital defect or my be associated with other anomalies, such as Down syndrome and genitourinary abnormalities.

Causes

The cause of congenital megacolon may be either failure of migration of the cells of the embryonic neural crest into the wall of the intestine or the failure of the plexuses to progress in a craniocaudal direction within the intestinal wall. The result is functional obstruction of the colon due to a lack of peristalsis, leading to the accumulation of feces and gas proximal to the defect. Since the colon enlarges or becomes distended, the condition is called megacolon. In most infants, the aganglionic segment is limited to the rectosigmoid colon.

Sign and symptoms

The symptoms of congenital megacolon vary from acute obstruction in the newborn to chronic constipation in the older child.

In Newborn infants

• Failure to pass meconium
• Abdominal distention
• Refusal to suck
• Bile-stained vomitus
• Failure to take fluids leads to weight loss and dehydration.

In children

• Failure to gain weight and delayed growth.
• Abdominal distention
• Vomiting
• Constipation alternating with diarrhea.
• Ribbon-like and foul-smelling stools.

Complications

• The most serious complication is enterocolitis; signs include fever, gastrointestinal bleeding and explosive watery diarrhea.
• Peritonitis
• Colonic perforation
• Sepsis and septic shock
• Chronic constipation leads to fecal impaction
• Electrolyte imbalances

Diagnosis

The diagnosis can be suspected on the basis of the history and physical examination, can be made on the basis of a barium enema when the difference in size between the ganglionic and aganglionic bowel is observed, and can be conclusively confirmed on the basis of a rectal biopsy. If the biopsy shows absent ganglion cells in the submucosa and intermuscular nerve plexuses with or without increased numbers of nerve fibers, the child has megacolon.

Treatment

Treatment for mild or moderate disease is based on relieving the chronic constipation with stool softeners and rectal irrigations; however many children require surgery.

Maintain a low-fiber, high-calorie, high-protein diet; parenteral nutrition may be necessary in extreme situations. Nurse administer stool softeners as prescribed and administer daily rectal irrigations with normal saline to promote adequate elimination and prevent obstruction as prescribed. 

Treatment for moderate to severe disease involves a two-step surgical procedure.

1. Initially, in the neonatal period, a temporary colostomy is created to relieve obstruction and allow the normally innervated, dilated bowel to return to its normal size.
2. When the bowel returns to its normal size, a complete surgical repair is performed via a pull-through procedure to excise portions of the bowel; at this time, the colostomy is closed.

Preoperative intervention

• Assess the bowel function.
• Maintain NPO status.
• Monitor hydration and fluid and electrolyte status; provide fluids intravenously as prescribed for hydration.
• Administer antibiotics or colonic irrigations with an antibiotic solution as prescribed to clear the bowel of bacteria.
• Monitor strict intake and output.
• Obtain daily weight.
• Measure abdominal girth daily.
• Avoid taking the temperature rectally.
• Monitor for respiratory distress associated with abdominal distention.

Postoperative intervention

• Monitor vital signs, avoiding taking the temperature rectally.
• Measure abdominal girth daily or when required.
• Assess the surgical site for redness, swelling and drainage.
• Assess the stoma if present for bleeding or skin breakdown (stoma should be red and moist).
• Assess the anal area for the presence of stool, redness, or discharge.
• Maintain NPO status as prescribed and until bowel sounds return or flatus is passed, usually within 48 to 72 hours.
• Maintain nasogastric tube to allow intermittent suction until peristalsis returns.
• Maintain IV fluid until the child tolerates appropriate oral intake, advancing the diet from clear liquids to regular as tolerated.
• Assess for dehydration and fluid overload.
• Monitor strict intake and output.
• Assess for pain and provide comfort measures as required.
• Provide the parents with instructions regarding colostomy care and skin care.
• Teach the parents about the appropriate diet and the need for adequate fluid intake.