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.