Hirschsprung disease

Hirschsprung disease is a congenital disorder in which enteric nerve cells are absent from a segment of the colon. The affected segment cannot relax and move stool normally, causing functional obstruction.

Enteric nervous system: The network of neurons and support cells embedded in the gastrointestinal tract that regulates digestion. Its ganglion cells are absent from the affected bowel segment.
Rectal suction biopsy: A minimally invasive procedure that removes a small rectal tissue sample for microscopic examination. It can establish the diagnosis by showing absent ganglion cells.
RET proto-oncogene: A gene encoding a receptor tyrosine kinase involved in cell signaling and development. Pathogenic variants in RET are a major genetic cause of Hirschsprung disease.
Short-segment Hirschsprung disease: Hirschsprung disease in which aganglionosis is limited to the rectum and a short portion of the sigmoid colon. This is the most common anatomical pattern.
Neural crest: An embryonic cell population that migrates and forms diverse structures, including much of the enteric nervous system. Enteric nerve cells normally migrate from neural crest into the developing bowel.
Anorectal manometry: A test that measures pressure and reflex responses in the rectum and anal sphincters. Failure of the rectoanal inhibitory reflex can support suspicion of the disease.
EDNRB: A gene encoding the endothelin B receptor, which contributes to neural crest cell development and migration. Variants can disrupt formation of enteric ganglion cells.
Long-segment Hirschsprung disease: Hirschsprung disease in which aganglionosis extends beyond the rectosigmoid colon. A longer affected segment can produce more extensive bowel dysfunction.
Intestinal peristalsis: Coordinated waves of intestinal muscle contraction that propel contents through the digestive tract. The aganglionic segment cannot coordinate the propulsion needed to pass stool.
Contrast enema: An imaging examination that fills the colon with contrast material to show its shape and passage of contents. It may reveal a narrow distal segment and dilated bowel above it.

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