What causes What I need to know about Hirschsprung Disease ?
People with HD have constipation because they lack nerve cells in a part or all of the large intestine. The nerve cells signal muscles in the large intestine to push stool toward the anus. Without a signal to push stool along, stool will remain in the large intestine.
                
How severe HD is depends on how much of the large intestine is affected. Short-segment HD means only the last part of the large intestine lacks nerve cells. Long-segment HD means most or all of the large intestine, and sometimes the last part of the small intestine, lacks nerve cells.
                
In a person with HD, stool moves through the large intestine until it reaches the part lacking nerve cells. At that point, the stool moves slowly or stops, causing an intestinal obstruction.