A 2-day-old neonate presents with abdominal distension and failure to pass meconium. Plain abdominal X-ray shows dilated loops of bowel. Contrast enema reveals a transition zone in the rectosigmoid with a 'bird's beak' appearance. Rectal biopsy confirms absence of ganglion cells in the myenteric and submucosal plexuses. This patient has Hirschsprung disease. The pathological process is best explained by:

• A Failure of parasympathetic innervation development from the sacral spinal cord
• B Premature arrest of craniocaudal migration of neural crest cells from the vagal region of the neural tube ✓
• C Absence of longitudinal (Auerbach's) plexus only with intact submucosal plexus
• D Hyperganglionosis of the internal anal sphincter

Explanation

Hirschsprung disease results from failure of craniocaudal migration of neural crest cells (from the vagal neural crest, levels 1-7 somites) that normally colonize the gut from proximal to distal. Arrest of migration leads to an aganglionic segment affecting BOTH the myenteric (Auerbach's) and submucosal (Meissner's) plexuses. The affected segment (typically rectosigmoid in 75%) is tonically contracted and narrow (pseudo-obstruction), while the proximal normally ganglionated bowel dilates. RET proto-oncogene mutations are found in ~50% of familial cases. The definitive operation (Swenson, Soave, or Duhamel pull-through procedure) removes the aganglionic segment.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.