Review Question - QID 218738

This patient who received poor prenatal care and presents with a failure to pass stool since birth, vomiting, and abdominal distention likely has meconium ileus. The abdominal radiograph showing dilated small bowel loops and the abnormal sweat chloride test indicative of cystic fibrosis confirm the diagnosis.

Meconium ileus is caused by obstruction of the terminal ileum with inspissated meconium. It most commonly occurs in patients with cystic fibrosis; up to 10% of neonates with cystic fibrosis present initially with meconium ileus. It presents clinically with a failure to pass meconium, abdominal distention, and vomiting. Plain film abdominal radiography is generally nonspecific but will usually show dilated small loops. The diagnosis can be secured by a hyperosmotic contrast enema which will show a point of obstruction in the terminal ileum and may show meconium pellets. All patients with meconium ileus should also receive testing for cystic fibrosis with sweat testing or genetic testing. Initial treatment consists of nasogastric decompression and correction of fluid and electrolyte abnormalities. Subsequent definitive treatment can be non-operative (a hyperosmolar enema) or operative (enterotomy with lavage, double enterostomy, resection of affected bowel).

Long et al. studied factors associated with successful non-operative management of meconium ileus in cystic fibrosis. The authors found that patients with successful enema decompression are more likely to undergo repeat enemas than those who proceeded to laparotomy. The authors recommend adequate hydration and placement of an intravenous line before initiating non-operative management of meconium ileus.

Figure/Illustration A shows non-specific dilated bowel loops proximal to the site of meconium impaction (red circle). The classic “bubbly” appearance of the distended intestinal loops is indicated by the blue circles.

Incorrect Answers:
Answer 1: Fibrosing colonopathy is a severe fibrotic process associated with intestinal strictures in patients with cystic fibrosis who take large doses of pancreatic enzyme replacement therapy (PERT). This condition is rare today due to decreased PERT dosing and would not be expected in a patient not currently taking PERT.

Answer 2: Hirschsprung disease presents with vomiting, constipation, and delayed stool passage with meconium. Patients may exhibit forceful expulsion of stool after a rectal exam. Hirschsprung disease typically presents with a transition point in the colon, not in the terminal ileum. Furthermore, Hirschsprung disease is not associated with cystic fibrosis.

Answer 3: Intussusception is occasionally found in patients with cystic fibrosis. It usually presents with colicky pain, vomiting, a palpable abdominal mass, and rectal bleeding. On radiography, one may occasionally see an elongated soft tissue mass with proximal bowel obstruction.

Answer 4: Malrotation presents with vomiting, distention, and abdominal tenderness. Malrotation is not associated with cystic fibrosis. Plain film abdominal radiography is usually unremarkable, although malrotation may sometimes be complicated by volvulus.

Bullet Summary:
Meconium ileus presents in patients with cystic fibrosis with a lack of meconium, abdominal distention, and radiographic evidence of dilated small bowel loops.