During normal prenatal development, cells from the neural crest migrate into the large intestine (colon) to form the networks of nerves called the myenteric plexus (Auerbach plexus) (between the smooth muscle layers of the gastrointestinal tract wall) and the submucosal plexus (Meissner plexus) (within the submucosa of the gastrointestinal tract wall). In<unk><unk> , the migration is not complete and part of the colon lacks these nerve bodies that regulate the activity of the colon. The affected segment of the colon cannot relax and pass stool through the colon, creating an obstruction. The most accepted theory of the cause of<unk>  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<unk> . With<unk> , the segment lacking neurons (aganglionic) becomes constricted, causing the normal, proximal section of bowel to become 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 most cited feature is absence of ganglion cells: notably in males, 75% have none in the end of the colon (rectosigmoid) and 8% lack ganglion cells in the entire colon. The enlarged section of the bowel is found proximally, while the narrowed, aganglionic section is found distally, closer to the end of the bowel. The absence of ganglion cells results in a persistent overstimulation of nerves in the affected region, resulting in contraction. The equivalent<unk>  in horses is lethal white syndrome.
Hirschsprung's disease
Meconium
Retained antrum syndrome
Intestinal pseudo-obstruction
Hartnup disease
Necrotizing enterocolitis
Meckel's diverticulum
Intestinal malrotation