Which is a common cause of lower GI bleeding?

Lower gastrointestinal (GI) bleeding typically originates from any part of the gastrointestinal tract that is located after the duodenum, with common sources including the colon and rectum. Diverticular disease is a well-known cause of lower GI bleeding because diverticula—small pouches that can form in the walls of the colon—can become inflamed or can rupture, leading to bleeding. This condition is often associated with symptoms such as abdominal pain and changes in bowel habits, and bleeding can be significant, leading to visible blood in the stool.

In contrast, the other options do not commonly lead to lower GI bleeding. Pneumonia primarily affects the lungs, and while it can have systemic effects, it is not directly related to GI bleeding. Cirrhosis involves liver dysfunction and can lead to upper GI bleeding due to varices or portal hypertension, but it does not typically cause bleeding in the lower GI tract. Cholecystitis involves inflammation of the gallbladder, which can cause abdominal pain but does not normally result in bleeding in the lower gastrointestinal system. Therefore, diverticular disease stands out as a direct and common cause of lower GI bleeding.