Diverticulitis is a common digestive disease which involves the formation of pouches (diverticula) within the bowel wall. This process is known as diverticulosis, and typically occurs within the large intestine, or colon, although it can occasionally occur in the small intestine as well. Diverticulitis results when one of these diverticula becomes inflamed.People often have left lower quadrant abdominal pain and tenderness, fever, and an increased white blood cell count.