- Hirschsprung Disease is a congenital anatomic abnormality of development in which defects of neural crest cell migration results in the absence of neural innervation in a distal segment of the large intestine, thus producing a functional bowel obstruction.
- Recall from Basic GI Motility Mechanisms that bowel motility is primarily coordinated by the neural crest cell-derived enteric nervous system, specifically the myenteric plexus. Neural crest cells normally migrate caudally, reaching the rectum and anus last. In Hirschsprung Disease, defective neural crest cell migration results in the absence of the enteric nervous system in the distal segments of the large intestine, usually affecting the rectum and the sigmoid colon, resulting in a functional bowel obstruction. Consequently, although there is nothing physically blocking the bowel, defective alimentary tract motility essentially acts as a de facto obstruction. Feces becomes impacted just above the aganglionic portion, accumulating and over time distending the large intestine.
- Hirschsprung Disease is characterized by a complete absence of the enteric nervous system, meaning the submucosal and myenteric plexuses, in affected areas. Over time megacolon develops, defined as distention of the large intestine by more than 6cm and occurs due to accumulation of impacted feces.
- Hirschsprung Disease presents very early in life as a delay in passage of meconium in neonates. If left untreated this is followed by vomiting several days later.