Lower Gastrointestinal (GI) Series

Illustration of the digestive system with the colon and rectum highlighted.A lower gastrointestinal (GI) series uses x rays to diagnose problems in the large intestine, which includes the colon and rectum. The lower GI series may show problems like abnormal growths, ulcers, polyps, and diverticuli, and colon cancer.

Before taking x rays of your colon and rectum, the radiologist will put a thick liquid called barium into your colon. This is why a lower GI series is sometimes called a barium enema. The barium coats the lining of the colon and rectum and makes these organs, and any signs of disease in them, show up more clearly on x rays. It also helps the radiologist see the size and shape of the colon and rectum.

You may be uncomfortable during the lower GI series. The barium will cause fullness and pressure in your abdomen and will make you feel the urge to have a bowel movement. However, that rarely happens because the tube used to inject the barium has a balloon on the end of it that prevents the liquid from coming back out.

You may be asked to change positions while x rays are taken. Different positions give different views of the intestines. After the radiologist is finished taking x rays, you will be able to go to the bathroom. The radiologist may also take an x ray of the empty colon afterwards.

A lower GI series takes about 1 to 2 hours. The barium may cause constipation and make your stool turn gray or white for a few days after the procedure.

Preparation
Your colon must be empty for the procedure to be accurate. To prepare for the procedure you will have to restrict your diet for a few days beforehand. For example, you might be able to drink only liquids and eat only nonsugar, nondairy foods for 2 days before the procedure; only clear liquids the day before; and nothing after midnight the night before. A liquid diet means fat-free bouillon or broth, gelatin, strained fruit juice, water, plain coffee, plain tea, or diet soda. To make sure your colon is empty, you will be given a laxative or an enema before the procedure. Your physician may give you other special instructions.