A newborn presents with a lower bowel obstruction. The most likely cause is which condition?

• A. Low-fiber diet
• B. Lactose intolerance
• C. Hirschsprung Disease
• D. Fecal impaction

Answer: (C)

Hirschsprung disease is the most likely cause of a lower bowel obstruction in a newborn. It happens when neural crest cells fail to migrate into the distal colon, leaving an aganglionic segment that cannot relax. That functional lack of relaxation creates a blockage: stool and gas build up proximal to the aganglionic zone, leading to abdominal distension and bilious vomiting. Clinically, these babies often don’t pass meconium within the first 24 to 48 hours of life. Imaging may show a transition from a narrow, constricted distal rectum to a dilated proximal colon, and the definitive diagnosis is rectal biopsy showing absence of ganglion cells. Treatment involves surgical removal of the aganglionic segment with reattachment (pull-through).

A low-fiber diet isn’t a neonatal issue, lactose intolerance typically causes diarrhea rather than obstruction in newborns, and fecal impaction is more common later in childhood; they don’t fit the newborn presentation as well as Hirschsprung disease.