An anal fistula is an abnormal tunnel between the inside of the anal canal and the skin nearby. It often develops after an anal abscess, which is a pocket of infection near the anus or rectum. This page is retained for general education; anal fistula surgery is not a current Zadeh Surgical service.
How does an abscess become a fistula?
Small glands inside the anus can become blocked and infected. The infection may collect as an abscess and cause pain, swelling, redness, or fever. After the abscess drains—either on its own or through a procedure—a tunnel can remain between the infected gland and the skin.
If the skin opening stays open, fluid or pus may drain intermittently. If it closes while the tunnel remains, another abscess can form. Not every abscess becomes a fistula, but repeated cycles of swelling, pain, drainage, and temporary improvement are a common clue.
An abscess usually needs drainage.
Antibiotics alone do not reliably empty a pocket of pus. Significant anal pain, swelling, fever, chills, or feeling acutely ill requires prompt medical evaluation.
What symptoms can an anal fistula cause?
- Repeated drainage of pus, blood, or fluid from an opening near the anus
- Skin irritation, itching, or moisture
- Pain and swelling that improve after drainage and then return
- A history of an abscess that was drained
- Fever or worsening pain if another abscess develops
How is it diagnosed?
A surgeon begins with the history and examination. The outer opening may be visible, although drainage can stop temporarily and make the tunnel harder to find. MRI or a specialized ultrasound can help map a complex fistula, locate a deep abscess, or show how the tract relates to the muscles that control bowel movements.
Crohn's disease, prior radiation, trauma, infection, and other less common conditions can change both the diagnosis and treatment plan.
Why does the path of the fistula matter?
The anal sphincter muscles help control gas and bowel movements. Some fistulas pass through little muscle; others cross a substantial portion. Treatment must balance curing the fistula with protecting bowel control. That is why one procedure is not appropriate for every fistula.
How is a fistula treated?
A simple fistula involving little sphincter muscle may be opened along its length so it can heal from the inside out; this is called a fistulotomy. A draining loop, called a seton, may be placed to control infection or prepare for another procedure. More complex fistulas may require a muscle-sparing operation, such as a LIFT procedure or an advancement flap.
Some treatments have a higher chance of recurrence, and more than one procedure may be needed. The best approach depends on the tract, prior operations, bowel-control function, and whether Crohn's disease or another condition is present.
What happens after treatment?
Wound care, warm-water baths, absorbent gauze, pain control, and keeping bowel movements soft may be part of recovery. The treating surgeon should explain expected drainage, activity limits, follow-up, and the warning signs of another infection.