A barium enema is an X-ray exam of your large intestine that uses a chalky liquid called barium sulfate to make your colon visible on imaging. Also called a lower GI series, it helps doctors spot abnormalities in the colon and rectum, from blockages and inflammation to tumors and pouches in the intestinal wall. The procedure typically takes 30 to 60 minutes and doesn’t require sedation.
How Barium Makes Your Colon Visible
Your colon doesn’t show up well on a standard X-ray. Barium sulfate is a dense, white liquid that coats the inner lining of your intestine and blocks X-rays from passing through, creating a clear outline of the colon’s shape and structure on the resulting images. Think of it like painting the inside of a pipe so you can photograph its contours. Any polyps, narrowing, pockets, or masses along the colon wall show up as irregularities in that coating.
Single-Contrast vs. Double-Contrast
There are two versions of this test, and each one is better suited to different situations.
A single-contrast barium enema fills the colon entirely with barium liquid, outlining the overall structure. It’s typically used when doctors are looking for bowel obstructions, fistulas (abnormal connections between organs), or an unusually enlarged colon.
A double-contrast (air-contrast) barium enema uses a smaller amount of thicker barium to coat the intestinal walls, then pumps air into the colon to expand it. The air improves contrast against the barium coating, producing more detailed images of the mucosal surface. This version is preferred when doctors are looking for tumors or small growths because it reveals finer surface details.
What the Procedure Feels Like
When you arrive, you’ll change into a hospital gown and lie on your side on an exam table. A radiologist or technician will gently insert a lubricated tube into your rectum. The tube has a small balloon near its tip that inflates slightly to keep the barium from leaking out.
Barium flows through the tube from a connected bag, gradually filling your colon. If you’re having the double-contrast version, air is pumped through the same tube afterward. Most people feel pressure, fullness, and moderate cramping during this part, similar to the urge to have a bowel movement. The air insufflation in a double-contrast exam can feel particularly uncomfortable, though it’s temporary.
You’ll be asked to turn into several different positions on the table so the barium coats your entire colon and the radiologist can capture images from multiple angles. You may need to hold your breath briefly for certain shots. The radiologist might also press firmly on your abdomen and pelvis to reposition sections of your colon for better visibility. Multiple X-rays are taken throughout.
Once imaging is complete, the balloon is deflated, the tube is removed, and most of the barium drains out. You’ll be able to use a restroom right away.
Preparing for the Exam
Your colon needs to be completely empty for the images to be useful. An X-ray is sometimes taken beforehand to confirm the bowel is clean. Preparation typically involves switching to a clear liquid diet the day before the procedure, taking a prescribed laxative or bowel-cleansing solution, and fasting after midnight. Your doctor’s office will give you specific instructions, which vary slightly between practices. Following them closely matters because any remaining stool can mimic polyps on the images or obscure real abnormalities.
What It Can and Can’t Detect
A barium enema is effective at identifying colon cancer, diverticulosis (small pouches in the colon wall), bowel obstructions, and large structural abnormalities. It’s also used to evaluate inflammatory bowel disease and fistulas.
Where it falls short is in detecting smaller growths. A study comparing air-contrast barium enemas to colonoscopy found that the barium exam detected only about 27% of polyps 10 mm or larger and just 8% of polyps 5 mm or smaller. For diverticula, however, the barium enema was actually more sensitive than colonoscopy. And for colon cancer specifically, accuracy was comparable between the two tests.
The key limitation is that a barium enema is purely diagnostic. If the radiologist spots a polyp or suspicious area, you’ll still need a colonoscopy afterward to biopsy or remove it.
How It Compares to Colonoscopy
Colonoscopy has largely replaced the barium enema for routine colon cancer screening because it can both detect and treat problems in a single session. A colonoscope lets the doctor see the colon directly, take tissue samples, and remove polyps on the spot.
A barium enema is less invasive and less expensive. It doesn’t require sedation, so you can drive yourself home and return to normal activities the same day. But it’s also less sensitive for detecting polyps, and patients don’t always find it more comfortable. The cramping from barium and air can be significant, and the bowel preparation is essentially the same as for a colonoscopy.
Today, barium enemas are more commonly ordered when a colonoscopy is incomplete (the scope couldn’t reach the entire colon), when a patient can’t safely undergo sedation, or when the clinical question involves structural issues like obstruction or fistulas rather than cancer screening.
Risks and Complications
Barium enemas are considered safe. In a review of roughly 134,700 procedures, 54 complications were reported, and three were fatal, yielding a mortality rate of about 1 in 44,900. The most serious risk is bowel perforation, which occurred in 16 of those cases (both inside and outside the abdominal lining). Cardiac events accounted for 20 complications, mostly in patients with preexisting heart conditions.
More common, less serious side effects include cramping during the exam, constipation afterward, and bloating from retained air. Barium can harden in the colon if it isn’t passed promptly, so drinking extra fluids in the hours and days after the test helps move it through.
What to Expect Afterward
You can eat and drink normally as soon as the exam is over. Your stools will appear white or light-colored for a day or two as your body expels the remaining barium. This is completely normal. Drinking plenty of water and other fluids helps prevent the barium from causing constipation, which is the most common post-procedure complaint. Some people also experience mild cramping or gas for the rest of the day, particularly after a double-contrast exam. If you notice any significant abdominal pain, fever, or inability to pass stool after several days, contact your doctor.