Pathophysiology
The most accepted theory of the cause of Hirschsprung is that there is a defect in the craniocaudal migration of neuroblasts originating from the neural crest that occurs during the first 12 weeks of gestation. Defects in the differentiation of neuroblasts into ganglion cells and accelerated ganglion cell destruction within the intestine may also contribute to the disorder.
This lack of ganglion cells in the myenteric and submucosal plexus is well-documented in Hirschsprung's disease. With Hirschsprung's disease, the segment lacking neurons (aganglionic) becomes constricted, causing the normal, proximal section of bowel to becomes distended with feces. This narrowing of the distal colon and the failure of relaxation in the aganglionic segment are thought to be caused by the lack of neurons containing nitric oxide synthase.
The equivalent disease in horses is Lethal white syndrome.
Read more about this topic: Hirschsprung's Disease