USMLE (United States Medical Licensing Examination): Step 1: Basic sciences assessment Practice Exam 08

A 2-day-old boy is evaluated for bilious vomiting and abdominal distension that began shortly after birth. Pregnancy and delivery were uncomplicated. Physical examination shows abdominal distension and decreased bowel sounds. Abdominal radiograph shows multiple dilated bowel loops with air-fluid levels. A contrast enema demonstrates a narrow distal rectosigmoid segment with a proximally dilated colon. Rectal suction biopsy shows absence of ganglion cells in the submucosal (Meissner) plexus. Which of the following best explains the underlying mechanism of this condition?