Congenital aganglionic megacolon, also known as Hirschsprung disease, is a motor disorder of the intestines caused by failure of neural crest cells to migrate completely during gestation. This results in aganglionic segments of colon, lack of colonic relaxation, and functional obstruction. Typically, this affects a short segment of the distal rectum but, in rare cases, may affect the entire colon.

Patients typically present in infancy with a 3:1-4:1 male predominance and association with other syndromes including trisomy 21, Bardet-Biedl syndrome, multiple endocrine neoplasia type 2 (MEN2), and congenital central hypoventilation syndrome. Exact genetic defects are very important for patient prognosis and genetic counseling. Due to the considerable overlap of congenital megacolon and hereditary syndromes, the genitourinary tract, hearing, and vision should be evaluated in all patients diagnosed with congenital megacolon.

Congenital megacolon is often diagnosed in the first several days of life. Most patients present in the neonatal period with failure to pass stool within the first 48 hours of life and the subsequent development of bilious emesis, abdominal distension, and rarely enterocolitis. This can progress to toxic megacolon, with high risk for perforation, intraabdominal infection, and sepsis.

Those with less severe disease may present in childhood with chronic constipation and failure to thrive.

Congenital megacolon is curative with surgical resection of the aganglionic bowel.