A barium enema is an X-ray exam that can detect changes or abnormalities in the large intestine (colon). The procedure is also called a colon X-ray.

An enema is the injection of a liquid into your rectum through a small tube. In this case, the liquid contains a metallic substance (barium) that coats the lining of the colon. Normally, an X-ray produces a poor image of soft tissues, but the barium coating results in a relatively clear silhouette of the colon.

During a barium enema exam, air may be pumped into the colon. The air expands the colon and improves the quality of images. This is called an air-contrast (double-contrast) barium enema.

Before a barium enema, your doctor will instruct you to completely empty your colon.

In the past, doctors used barium enema to investigate the cause of abdominal symptoms. But this test has mostly been replaced by newer imaging tests that are more accurate, such as CT scans.

In the past, your doctor may have recommended a barium enema to determine the cause of signs and symptoms, such as the following:

• Abdominal pain
• Rectal bleeding
• Changes in bowel habits
• Unexplained weight loss
• Chronic diarrhea
• Persistent constipation

Similarly, a barium enema X-ray previously may have been ordered by your doctor to detect such conditions as:

• Abnormal growths (polyps) as part of colorectal cancer screening
• Inflammatory bowel disease

A barium enema exam poses few risks. Rarely, complications of a barium enema exam may include:

• Inflammation in tissues surrounding the colon
• Obstruction in the gastrointestinal tract
• Tear in the colon wall
• Allergic reaction to barium

Barium enema exams generally aren't done during pregnancy because X-rays present a risk to the developing fetus.

Before a barium enema exam, you'll be instructed to empty your colon. Any residue in your colon may obscure the X-ray images or be mistaken for an abnormality.

To empty your colon, you may be asked to:

• Follow a special diet the day before the exam. You may be asked not to eat and to drink only clear liquids — such as water, tea or coffee without milk or cream, broth, and clear carbonated beverages.
• Fast after midnight. Usually, you'll be asked not to drink or eat anything after midnight before the exam.
• Take a laxative the night before the exam. A laxative, in a pill or liquid form, will help empty your colon.
• Use an enema kit. In some cases, you may need to use an over-the-counter enema kit — either the night before the exam or a few hours before the exam — that provides a cleansing solution to remove any residue in your colon.
• Ask your doctor about your medications. At least a week before your exam, talk with your doctor about the medications you normally take. He or she may ask you to stop taking them days or hours before the exam.

During the exam

During your barium enema, you'll wear a gown and be asked to remove eyewear, jewelry or removable dental devices. The exam will be performed by a radiology technician and a physician who specializes in diagnostic imaging (radiologist).

You'll begin the exam lying on your side on a specially designed table. An X-ray will be taken to make sure your colon is clean. Then a lubricated enema tube will be inserted into your rectum. A barium bag will be connected to the tube to deliver the barium solution into your colon.

If you're having an air-contrast (double-contrast) barium enema, air will flow through the same tube and into your rectum.

The tube that's used to deliver the barium has a small balloon near its tip. When positioned at the entrance of your rectum, the balloon helps keep the barium inside your body. As your colon fills with barium, you may feel the urge to have a bowel movement. Abdominal cramping may occur.

Do your best to hold the enema tube in place. To relax, take long, deep breaths.

You may be asked to turn and hold various positions on the exam table. This helps ensure that your entire colon is coated with barium and enables the radiologist to view the colon from various angles. You also may be asked to hold your breath at times.

The radiologist may press firmly on your abdomen and pelvis, manipulating your colon for better viewing on a monitor attached to the X-ray machine. A number of X-rays will likely be taken of your colon from various angles.

A barium enema exam typically takes about 30 to 60 minutes.

After the exam

After the exam, most of the barium will be removed from your colon through the enema tube. When the tube is removed, you'll be able to use the toilet to expel additional barium and air. Any abdominal cramping usually ends quickly, and you should be able to return to your usual diet and activities right away.

You may have white stools for a few days as your body naturally removes any remaining barium from your colon. Barium may cause constipation, so you may find you can reduce your risk of constipation by drinking extra fluids in the days following your exam. Your doctor may recommend a laxative, if needed.

Check with your doctor if you're unable to have a bowel movement or pass gas more than two days after the exam or if your stool doesn't return to its normal color within a few days.

The radiologist prepares a report based on the results of the examination and sends it to your doctor. Your doctor will discuss the results with you, as well as subsequent tests or treatments that may be required:

• Negative result. A barium enema exam is considered negative if the radiologist detects no abnormalities in the colon.
• Positive result. A barium enema exam is considered positive if the radiologist detects abnormalities in the colon. Depending on the findings, you may need additional testing — such as a colonoscopy — so that any abnormalities can be examined more thoroughly, biopsied or removed.

If your doctor is concerned about the quality of your X-ray images, he or she may recommend a repeat barium enema or another type of diagnostic test.