Master Hirschsprung Disease with Picmonic for Medicine

The rectum is always affected in Hirschsprung disease but the involvement of additional segments varies widely. Most cases are limited to the rectum and can involve the sigmoid colon but severe cases can involve the entire length of the colon.

Hirschsprung disease results when normal migration of neural crest cells is arrested prematurely around the cecum to the rectum. This causes a segment of the distal intestine to lack both the Meissner plexus in the submucosa and Auerbach myenteric plexus. These neurons are the major nerve supply to the GI tract and play an important role in controlling GI tract motility.

Because the Meissner and Auerbach plexus play an important role in controlling GI tract motility, Hirschrpung disease is characterized by uncoordinated peristalsis and functional obstruction of the gut causing chronic constipation.

Infants with Hirschsprung disease can present with failure to pass meconium due to uncoordinated peristalsis and functional obstruction of the gut.

Functional obstruction of the distal colon results in dilation proximal to the affected segment. With time, the proximal colon may become severely distended leading to megacolon.

10% of all cases of Hirschsprung disease occur in children with Down syndrome.

Mutations in RET are most notable for causing multiple endocrine neoplasia type 2 (MEN2). However, mutations in this gene are also notable for their role in Hirschsprung Disease. Epidemiological studies vary, but the co-occurrence of Hirschsprung Disease and RET mutations has been reported to be as high as 70%.