Diverticulitis refers to the infection and inflammation of the small bulges called diverticula that can form in the intestinal lining over time. Many people who have diverticula do not go on to develop symptoms or complications of the condition.

In suspected cases of diverticulitis, the following steps are taken to diagnose the condition:

A physical examination of the abdomen is carried out to check for pain and tenderness.

Blood tests are performed to check for signs of infection.

The doctor will need to rule out a variety of other conditions associated with abdominal pain such as colon cancer, irritable bowel disease, stomach ulcers, ovarian cancer, appendicitis, pelvic inflammatory disease and ischemic colitis.

A barium enema may be performed which involves coating the internal surface of the colon with barium, a liquid that shows up on X-rays. This contrast fluid helps to highlight the diverticula and any inflamed lining. The patient is given a laxative to clear out their bowel before the procedure. The barium liquid is then squirted through a tube inserted into the rectum and a series of X-rays is obtained.

A colonoscopy may be performed to check the inside of the colon for the presence of diverticula. For this procedure, a thin flexible tube called an endoscope is passed into the colon via the rectum. The endoscope has a light source and a camera at its tip that are used to examine the internal wall of the colon. A colonoscopy should not be performed during acute stage diverticulitis due to the risk of perforation.

A computed tomography (CT) scan is usually recommended as it can diagnose diverticular disease with 98% accuracy. This scan provides a series of high definition X-ray images that can be used to visualize any inflamed or infected tissue in the intestine. Usually, a contrast dye is administered either orally or intravenously to help highlight the organs being studied. The CT scan is used to check for thickening and inflammation of the intestinal wall, diverticula and other complications such as the formation of an abscess.