Hirschsprung Disease Basics

Hirschsprung disease is congenital aganglionosis: ganglion cells are absent from the submucosal (Meissner) and myenteric (Auerbach) plexuses in a distal segment of bowel. Without these enteric nerve cells, the affected segment cannot coordinate peristalsis or relax normally. It stays functionally narrowed while stool and gas accumulate above it. The result is a functional obstruction, not a removable plug. The length of aganglionic bowel varies. Proximal bowel may become progressively dilated, so abdominal distention is a consequence of the distal problem rather than the primary disease. In a newborn, limited fluid reserves and rapid changes in abdominal pressure make deterioration possible before the infant appears profoundly ill. This mechanism also explains the absent recto-anal inhibitory reflex: when the rectum is distended, the normal relaxation response is missing because the relevant ganglion cells are absent.