MECKEL'S DIVERTICULUM - The embryological remains of the yolk stalk, when persisting abnormally as a blind sac or pouch in the child or adult, is located on the ileum (small intestine) a short distance above the cecum. It may contain gastric mucosa, that in some instances, can ulcerate, bleed, and perforate. For this reason, it is considered a relatively rare cause for bleeding and abdominal pain.