Hirschsprung disease (aganglionic megacolon) occurs when certain nerve cells in the wall of the colon do not form the right way when the fetus is growing.

In a person who does not have Hirschsprung disease, large muscles move gas and stool through the colon with the help of nerve cells called ganglion cells. Children with Hirschsprung disease do not have ganglion cells in the rectum. They sometimes do not have them in other parts of the colon either. Therefore, gas and stool get backed up. This can cause partial or total bowel obstruction. They can have problems passing gas and stool. Almost all children with Hirschsprung disease will need surgery.

The levels of Hirschsprung disease include:

  • Ultrashort segment: Missing ganglion cells in the last one to two centimeters of the rectum.
  • Short-segment: Missing ganglion cells in the rectum and sigmoid colon (the last segment of the colon).
  • Long-segment: Also missing ganglion cells in the first third of the colon.
  • Total colonic aganglionosis: Lack ganglion cells throughout the colon. This level is the least common. It causes more severe symptoms than other forms of the disease.