Illustration copyright 2000, 2003 Nucleus Communications, Inc. All rights reserved. http://www.nucleusinc.com

In Hirschsprung's disease, certain nerve cells (ganglion cells) in a portion of the colon are missing. Because the muscles in that area can't relax, the muscle contractions that normally push food and digestive waste through that part of the colon can't occur. The picture on the right shows a colon in which the rectum lacks ganglion nerve cells, causing swelling in the area above it.