What is Meckel's diverticulum? My dad was recently diagnosed with it.

D.G.

Meckel's diverticulum (MD), a usually harmless birth defect affecting the small intestine, is estimated to be present in 1-3 percent of the population. These people have a short, abnormal loop in the small intestine near the point where it joins the large intestine. When a fetus is growing in the womb, there is a connection between the umbilicus and fetal yolk sac that normally disappears by the eighth week of development. If this process goes awry, it leads to creation of an MD loop.

The inner lining of the MD loop is often unusual. Instead of being made of small intestine cells, the lining may resemble cells found in the stomach, pancreas, colon or liver. In most patients, MD causes no symptoms. It is often noticed only when an abdominal operation is performed for another reason.

However, complications of MD can occur in some people. The most common problem is bleeding, which can result in large amounts of blood being passed through the rectum. The cause of the bleeding can be an ulcer in the MD loop or in part of the adjacent small intestine, usually as a result of acid produced by the stomach-like cells in the MD loop. Another potential complication is obstruction of the loop, which can cause severe abdominal pain similar in nature to appendicitis. Surgical removal is the standard treatment for any MD loop that is causing problems.