An MR Defecography is a specialized MRI scan that focuses on how the pelvic floor — the group of muscles that support the bladder, womb, and rectum — works during a bowel movement.
Unlike a standard pelvic MRI, which only shows the pelvic floor at rest, an MR Defecography captures images while you squeeze, push, and pass simulated stool. This allows doctors to see exactly how the muscles move and where the problem lies.
Doctors request this scan when investigating long-standing constipation, difficulty passing stool, a sense of prolapse, or leakage of stool or urine that has not been explained by other tests.
Why would my doctor ask for an MR Defecography?
Your doctor may recommend an MR Defecography to look closely at how your pelvic floor functions, especially if you have:
- Long-standing constipation or a sense that you cannot fully empty your bowels.
- A feeling that something is bulging or coming down inside the rectum or vagina.
- Stool or urine leakage that has not been fully explained.
- Pain or pressure low in the pelvis during or after bowel movements.
- Recurring problems after pelvic floor surgery.
- Symptoms suggesting more than one pelvic floor problem at the same time (such as both constipation and prolapse).
What can an MR Defecography detect?
An MR Defecography helps doctors visualize:
- The position and movement of the bladder, uterus, vagina, and rectum during pushing and emptying.
- The pelvic floor muscles and how they relax and contract.
- The relationship between the different pelvic organs as you bear down.
It is particularly useful for identifying:
- Rectocele (a bulge of the rectum into the vagina).
- Cystocele (a bulge of the bladder into the vagina).
- Uterine or vaginal prolapse.
- Enterocele (loops of small bowel pushing down between the rectum and vagina).
- Rectal intussusception (the rectum folding inside itself during emptying).
- Pelvic floor muscles that fail to relax properly during a bowel movement.
- Multiple problems happening at the same time — which is common, and easy to miss without this scan.
Do I need any special preparation for an MR Defecography?
Yes, this scan requires some specific preparation:
- A small enema is usually given an hour or so before the scan to empty your lower bowel.
- The rectum is then gently filled with a thick gel (similar to ultrasound gel) just before the scan starts. This gel mimics stool and helps the radiologist see exactly what happens during emptying.
- Remove all jewelry, body piercings, and metal objects, and change into a hospital gown.
- You can eat and drink normally before the scan unless told otherwise.
Will I be injected with dye for this scan?
No. The "contrast" used for MR Defecography is the gel placed in the rectum, not an injection. Gadolinium dye is not needed for this scan.
What does an MR Defecography feel like?
The scan itself is painless, but it is one of the more unusual MRI experiences. You will lie on a padded table that slides into the MRI scanner.
Once inside, the radiographer will ask you to do three different things at different points during the scan:
- Lie still and relax — to capture the resting position.
- Squeeze your pelvic floor muscles as if you are stopping a bowel movement — to capture muscle strength.
- Push and bear down, then actually empty the gel from your rectum — to capture the pelvic floor in action.
It is completely normal to feel uncomfortable or embarrassed at the idea of emptying inside the scanner. Pads are placed underneath you to keep you clean and dry, and the team is fully used to performing this scan. The most important thing is to push properly when asked — a half-hearted effort gives a scan that does not answer the question, and the team would rather repeat the squeeze and push than have you hold back.
The machine makes loud knocking and humming sounds during the scan. Earplugs or headphones will be provided.
Is it safe for pregnant women or children?
This scan is rarely needed in pregnancy. If pelvic floor symptoms appear during pregnancy, they are usually managed conservatively first and reassessed after delivery. In children, MR Defecography is occasionally used for specific congenital conditions, but only when other tests cannot answer the question.
MRI itself uses no radiation and is safe; the gel used in the rectum is also safe.
How long does an MR Defecography take?
The scan usually takes 30 to 45 minutes. Including preparation, the whole appointment is usually one to two hours.
When will I get my results?
After the scan, a Radiologist with experience in pelvic floor imaging will review the images and prepare a detailed report. Results are typically ready within a few days. Because the findings often involve more than one problem and several specialties, your doctor may want to discuss the scan with a colorectal surgeon, urogynaecologist, or pelvic floor physiotherapist before deciding on treatment.
Why do I have to push and empty inside the scanner?
This is the part that makes the scan worth doing. Many pelvic floor problems — such as rectoceles, prolapse, or muscles that fail to relax — only become visible when you actually try to empty. A scan that only looks at the pelvic floor at rest can completely miss them. Pushing inside the scanner allows the radiologist to see exactly what is happening during emptying and to identify problems that cannot be seen any other way.
Will I be expected to fully empty in the scanner? Isn't that embarrassing?
Yes, you will be asked to fully empty the rectal gel inside the scanner — and yes, many patients find the idea embarrassing. It helps to know that the team performs this scan regularly and treats it as a routine medical test. The gel is clean, pads are placed underneath you to keep everything contained, and the radiographer will not be in the room with you during the emptying sequence. Holding back gives a poor scan that may have to be repeated; pushing properly gives the answers you came for. Most patients report afterwards that the experience was much less awkward than they feared.
What if I can't push hard enough during the scan?
This is common — the unfamiliar position, the noise, and the self-consciousness of being inside the scanner all make it harder to bear down naturally. The radiographer will coach you between sequences and may repeat the push attempt a second time. If you genuinely cannot push, that itself is useful information for the radiologist, because pelvic floor muscles that refuse to relax (a condition called dyssynergia) is one of the things the scan is looking for. Do your honest best, communicate with the team, and trust that they have seen every variation before.
What if I'm nervous about being inside the scanner?
It is normal to feel anxious about this scan — both because of the MRI machine and because of the nature of the test. The radiographer will be in contact with you the entire time, and you can hold a squeeze ball to alert them if you need a break. If you are very claustrophobic, ask your doctor about a mild sedative beforehand.
Conclusion
An MR Defecography is a safe, radiation-free, and uniquely informative way to investigate long-standing pelvic floor problems. It is one of the few tests that shows the pelvic floor doing its job — and the answers it provides often unlock a clear treatment plan after years of symptoms with no clear cause. The scan can feel awkward, but the information it gives can be genuinely life-changing.