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What is an MRI fistulogram? 

Magnetic resonance imaging (MRI) scan fistulogram is an imaging technique performed before surgery in people with conditions such as anal, anovaginal or rectovaginal fistulas.

An anal fistula is a relatively uncommon condition in which a small tunnel develops from the inside of the anus to the skin near it. It usually develops from an infection in the glands just inside the anus that forms a collection of pus (abscess). When the pus makes its way from the infected gland to the skin and drains out, it leaves a tunnel behind. The anal fistula does not go away on its own and needs surgery in most cases.

Anovaginal and rectovaginal fistulas are tracts formed between the anus or rectum and the vagina. It occurs due to radiation therapy, inflammatory bowel disease or surgical trauma.

An MRI scan gives detailed images of the internal structures of the body using a strong magnetic field and radio waves.

An MRI fistulogram helps in determining the location and course of the fistula tracts. It also helps in detecting the presence of any abscesses that may have formed and in assessing the site of the internal and external openings of the fistula before surgery.

  1. Who cannot have an fistulogram MRI?
  2. Why is an fistulogram MRI done?
  3. How should one prepare for an fistulogram MRI?
  4. What is the procedure for an fistulogram MRI?
  5. How does an fistulogram MRI feel?
  6. What do the results of the fistulogram MRI mean?
  7. What are the risks and benefits of the fistulogram MRI?
  8. What happens after the MRI fistulogram?
  9. What other tests can be done with the MRI fistulogram?
Doctors for Fistulogram MRI

People with the following medical implants cannot have an MRI scan without being evaluated for safety:

  • Certain kinds of metal coils placed within blood vessels
  • Ear implants
  • Pacemakers and cardiac defibrillators
  • Certain types of clips that are used for brain aneurysms
  • An artificial joint

An MRI is also usually avoided during the first trimester of pregnancy.

An MRI fistulogram is the best option for the diagnosis of an anal fistula. The scan is also a good option for the diagnosis of anovaginal and rectovaginal fistulas.

The scan may help in the following:

  • To detect the fistula tracts
  • To identify the associated abscesses
  • To plan surgery for fistula

The doctor may order this test if they notice the following symptoms of anal fistulas: 

Your doctor may also order this scan if you have the following symptoms of anovaginal or rectovaginal fistulas:

  • Vaginal discharge
  • Vaginitis (inflammation of the vagina)
  • Passage of feces and gas through the vagina

A contrast-enhanced MRI fistulogram can be performed for conditions like Crohn’s disease as it can assess and monitor the progress of the disease.

A non-contrast-enhanced MRI fistulogram can be used immediately post-operation to evaluate the procedure. The fat-containing grafts used to fill the fistulas during surgery can be readily observed on an MRI without contrast as opposed to a fistula, which requires a contrast medium to be seen clearly. A non-contrast MRI also helps view the residual tract of a fistula and can help differentiate it from hemorrhage (bleeding) in the immediate postoperative period since hemorrhage appears more intense on a non-contrast MRI.

You can take food and medicines as usual unless instructed otherwise. You may be asked to wear a hospital gown for the scan, or you may be allowed to wear your clothes if they are loose and without any metallic details.

Inform your doctor if you are pregnant, have recently had any surgery or have any other health problems.

Metal objects are not allowed in the scan room as they can be affected by the magnetic field and pose a safety risk. Leave the following belongings outside the MRI scan room:

  • Jewellery, credit cards and body piercings
  • Hearing aids, eyeglasses and removable dental work
  • Hair accessories, metal zippers and any other metal items
  • Pens and pocket knives
  • Watches, mobile phones and other electronic items

Tell your doctor if you have any implanted medical device so that it can be checked for MRI compatibility. Talk to your doctor if you have any shrapnel, bullets or other metal objects in your body, especially near your eye, as it may heat up or move during imaging and lead to blindness

If you are afraid of closed spaces, your doctor may give you a sedative before the test.

For contrast MRI, a gadolinium contrast dye may be used. Inform your doctor if you have any allergies or asthma.

If you are allergic to the contrast dye, the doctor may prescribe medication before the scan. If you have conditions such as severe kidney disease, a special contrast dye is needed. Tests to determine if your kidneys are working properly may be performed before the scan.

The following procedure is performed for an MRI fistulogram:

  • You will be positioned on a movable examination table. Straps may be used to help you stay still during the scan.
  • A device containing coils that can send and receive radio waves will be placed around the region to be scanned.
  • You will then be moved into the centre of the scanner, and a technologist will work at a computer outside the room to take the images.
  • A gadolinium contrast rectal enema is sometimes administered using a catheter, especially if there is a doubt that all the fistulas are not visible on the scan. 
  • The catheter will be removed, and you will be asked to pass stool. This is done to force the contrast through the fistulas due to the increased rectal pressure. 
  • The scan is repeated after that.

The scan usually takes half an hour to 50 minutes.

The MRI procedure is painless but you may feel a little uncomfortable while lying still for the duration of the procedure. 

The machine can be noisy when images are being taken but you will be provided with earplugs to reduce the sounds. The part of your body being scanned may feel a little warm, but this is normal.

The results of an MRI fistulogram help to confirm the presence of the following types of fistulas:

  • Perianal fistulas
  • Anovaginal fistulas
  • Rectovaginal fistulas

The benefits of an MRI fistulogram are:

  • Accuracy in the assessment of fistulas
  • Aids in precise planning of the surgery for fistulas
  • Non-invasive
  • Provides enough information to avoid invasive procedures
  • No radiation exposure

The following are the risks of fistulogram MRI:

  • The strong magnetic field may affect the functioning of implanted devices or distort the images. 
  • Exposure to strong magnetic fields during the first trimester of pregnancy may pose a risk for the unborn baby.

If sedation is not given, you do not need a recovery period and you may continue with your routine activities after the test.

The following tests can be performed with an MRI fistulogram:

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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