Defecography is a study of your body mechanics when you poop. X-ray or MRI images examine your muscles and organs in action to help determine the cause of pooping disorders, such as constipation and incontinence.
If you’re having trouble pooping — or holding in your poop — or any kind of unwanted sensation when you poop — your healthcare provider may recommend defecography to find out what the problem is. Defecography is a radiology test to look inside at your muscles and organs while you poop (defecate). Through detailed fluoroscopic X-ray or magnetic resonance imaging (MRI), healthcare providers can see how different muscles and organs are moving when you poop.
You don’t actually poop real poop in the test. Instead, healthcare technicians will fill your rectum with a barium paste — a medical substance that has the same consistency as poop. Barium is a contrast agent that makes your insides show up better in X-ray or MRI tests. You’ll evacuate the paste on a special toilet inside a scanning machine. The radiologist will be looking at your insides on a computer screen, not at you squatting on the toilet.
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The purpose of the test is to give your healthcare provider more information about how things are working when you poop, in order to diagnose and treat your problem. They may need to see:
Your healthcare provider may recommend a defecography to help determine the cause of longstanding unexplained symptoms when you poop, such as:
They may also use the test to help diagnose a suspected condition, such as:
All X-ray and MRI exams are performed by certified radiologists specially trained to operate and interpret the test results. Defecography in particular is performed by a specialist experienced in understanding anorectal motility.
Defecography can be done by fluoroscopic X-ray or by MRI. Both kinds of imaging can visualize the inside mechanics of your body as you poop. X-ray is more commonly used, but some people may need to avoid the small radiation exposure that it produces.
A fluoroscopic X-ray is like a video X-ray. Instead of taking isolated snapshots, fluoroscopy passes a continuous X-ray beam through the body, which produces continuous images on a screen in real-time. So rather than developing photographs, healthcare providers can view a video of your organs in action.
MRI (magnetic resonance imaging) works with radio waves and a magnetic field. Metal coils throughout the machine produce a magnetic field through electric current, which moves hydrogen atoms in your body. As they move back into place, they transmit a signal that the machine interprets through radio waves, producing an image on a computer.
Your healthcare provider will carefully record your medical history, including relevant surgeries and conditions, medications that you take and implants that you may have. They’ll ask you to describe in detail exactly what happens when you poop.
Then they will describe the procedure in detail and explain how you can collaborate during the test to help achieve the clearest results. The success of the test will depend on your cooperation.
Your healthcare provider may give you an enema to take at home to clear out your bowels before the test. They may also ask you to modify your diet, medications and water intake before the test. Guidelines vary, so follow the advice of your provider.
Whether you are taking a fluoroscopic X-ray defecography or an MRI defecography, both tests require some kind of contrast agent to highlight the internal organs that your healthcare provider wants to see. That means the contrast agent has to get inside of you before the test.
To visualize the last part of your digestive tract — the colon, rectum and anus — your healthcare team will prepare the agent (barium sulfate) as a paste to put into your anus. You’ll receive the barium enema immediately before the test. However, your healthcare provider may want to see other organs that the enema can’t reach.
If they need to see your small intestine, you might have to swallow a contrast solution. You might have to take it several hours before the test to give it enough time to travel through your digestive tract. Sometimes they may also need to see the wall between your vagina and anus. In this case, they may apply barium paste to your vagina.
After changing into a hospital gown, you’ll proceed to the testing room, where you’ll lie on a table. Your healthcare team will inject barium paste into your anus with something resembling a caulking gun. You may feel mild bloating or cramping from the enema. When your anus is full, you will feel the natural urge to defecate (poop), and you’ll be ready for the test.
If you are in an X-ray machine or an open MRI machine, your table will tilt vertically and a special toilet will be placed beneath you. You’ll sit on the toilet as you normally would. Both machines have an open and airy design to prevent any feelings of claustrophobia. If you are in a traditional MRI machine, which is more like a tube, you’ll remain horizontal on the table and poop into an adult diaper. A blanket with metal coils inside may be placed over you.
Some people feel claustrophobic inside a traditional MRI machine. You can ask for sedative medication to help you relax. The machine is well-lit and air-conditioned, and you can speak to your technician through an intercom if you need to. Both open and traditional MRI machines make loud popping and clicking noises while they record images. You will be offered earplugs or headphones in advance.
The radiologist operating the test equipment will give you instructions from outside the unit. They'll tell you when to squeeze, hold and relax your muscles as they record images. You’ll have to make sure to use enough force so that the technician can clearly see how your muscles engage when you push. You’ll also have to remain very still while each series of pictures is taken — usually for less than a minute.
The whole thing takes about 30 to 60 minutes. It might feel demanding or embarrassing, but it isn’t painful.
After the test, you’ll be brought to a private restroom where you can wash up. You may continue to see the white, chalky barium in your poop for the next day or so. You can resume your normal activities and diet immediately.
The small amount of radiation exposure from X-ray is considered safe, as long as it isn’t a regular occurrence. MRI poses no risks or side effects. If you are pregnant, it's standard practice to avoid both tests, if possible, even though the risk of harm to the fetus is very small.
The radiologist will send a detailed report to your primary healthcare provider, who will share the results with you. The report will reveal or rule out standard defecating disorders and address any specific concerns that your primary healthcare provider may have inquired into.
A note from Cleveland Clinic
If your healthcare provider has suggested a pooping study, chances are you've been having a difficult time with pooping for a while. Your defecography can provide essential information for your healthcare provider so that they can come up with the best plan of care to improve your pooping experience. It’s a little awkward, but if it leads to a successful diagnosis and treatment, it may bring relief in the end.
Last reviewed by a Cleveland Clinic medical professional on 01/10/2022.
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