Meckel's diverticulum is a small outpouching extending from the wall of the intestine and located in the lower portion of the small intestine. The pouch is a remnant of tissue from the embryonic development of the digestive system. The lining of this pouch is made up of either pancreatic tissue or acid-secreting tissue such as that seen in the stomach.

While Meckel's diverticulum is the most common congenital (present at birth) abnormality of the digestive system (present in 2 percent of the population), most people with this abnormality do not develop symptoms or problems. However, in some individuals, the secretion of acid by Meckel's diverticulum may cause peptic ulcers in the small intestinal lining. These ulcers can bleed or perforate (rupture), causing intestinal waste products to leak into the abdomen. This can result in a serious abdominal infection called peritonitis.

Meckel's diverticulum can also cause intestinal obstruction. It can do this by infolding on itself into the passageway of the intestine (intussusception). A portion of small intestine may also twist around an anchored Meckel's diverticulum. This is known as segmental volvulus and is associated with compromised blood supply and intestinal obstruction.