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Classification &
Types of Fistula

Not all fistulas are the same. They are classified based on their path relative to the anal sphincter muscles. Knowing the type is crucial because it determines whether the surgery will be Simple or Complex.

Medically Reviewed by Dr. Jaya Maheshwari
Last Updated: Jan 2026
Diagram of Fistula TypesAnatomy Diagram

The Golden Rule of Fistula Surgery

The main challenge in fistula surgery is to cure the track without damaging the sphincter muscles (which control bowel movements).

Simple FistulaCrosses little/no muscle. Easy to cure.
Complex FistulaCrosses major muscles. Needs Laser/VAAFT.

The 4 Main Types (Parks Classification)

Determined by MRI Fistulogram

Intersphincteric (Most Common)

45-50% of cases

The track passes between the two sphincter muscles. It is usually simple to treat and has a very high success rate with minimal risk to continence.

Transsphincteric

20-25% of cases

The track passes *through* both the internal and external sphincter muscles. Cutting this track openly carries a risk of incontinence, so Laser or VAAFT is preferred.

Suprasphincteric

Rare

The track goes *above* the sphincter muscles before opening into the rectum. These are complex and require staged surgeries or Seton placement.

Extrasphincteric

Very Rare

The track bypasses the sphincters entirely, often connecting the rectum to the skin. Usually caused by Crohn's disease or trauma.

Director's Interview

Simple vs Complex Fistula

Understanding your MRI Report

"Never rush into surgery for a complex fistula without mapping the track. If the muscle is cut wrongly, it can cause lifelong leakage problems."

Dr. Jaya Maheshwari explains what 'Grade' or 'Type' means in your MRI report and why Transsphincteric fistulas require specialized Laser treatment to prevent incontinence.

Vice President IAGES (2020–2022)
Trained in Germany & USA
Pioneer of Laser Proctology
Now Watching: Dr. Jaya on Advanced Treatments

Why it Matters?

The type of fistula dictates the treatment. Using a simple "cutting" surgery (Fistulotomy) on a complex fistula can lead to loss of bowel control.

Our Approach

We use sphincter-saving techniques (Laser / VAAFT) for all complex cases.

Have an MRI Report?

Send us your MRI report for a second opinion on the type of fistula.

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