What are Anal Fistulas?

What are Anal Fistulas?

Anal fistulas are small channels or connections that form between the anus and the external skin near the anus. Blocked or inflamed anal glands inside the anus can lead to an infection and abscess. Sometimes, the anal abscess drains on its own or it may need to be drained surgically. After the abscess has drained, the region may heal completely. If the wound persists or recurs, that raises suspicion that an underlying persistent fistula tract has not healed.

Most commonly, anal fistulas develop from an anal gland infection; in a minority of cases, a fistula may develop in the setting of inflammatory bowel disease (ie: Crohn’s disease), or after trauma, surgery, or radiation therapy near the anus.

Types of Anal Fistulas

  • Submucosal fistulas are superficial tracts inside the anal canal that do not involve any sphincter muscle
  • Intersphincteric fistulas start inside the anal canal, penetrate the internal sphincter muscle, and track between the internal and external sphincter muscles to an opening in the skin near the anal opening
  • Transsphincteric fistulas are tunnels that cross both the internal and external sphincter muscles to the external opening in the perianal skin
  • Suprasphincteric fistulas track between the internal and external sphincter, travel over top of the puborectalis muscle and back down to an opening in the perianal skin. Suprasphincteric fistulas can extend into a U shape around the anus with external openings on either side of the anus
  • Extrasphincteric fistulas travel downward from the rectum or sigmoid colon, through the levator muscles, completely around the sphincter muscles, and open in the skin around the anus. Extrasphincteric fistulas are rare and can be caused by intra-abdominal infections, such as diverticulitis or Crohn’s disease

Signs & Symptoms of Anal Fistulas


Anal fistulas can lead to cyclical swelling, pain, and drainage of fluid, blood, or pus from a chronic or recurrent wound around the anus. When facing symptoms of discomfort due to anal fistulas, our colorectal surgeons at NewYork-Presbyterian are here to help treat the symptoms.

Our specialists can help identify your condition based on your reported symptoms, evaluate with a physical exam, and recommend the best treatment for your care.

Symptoms of anal fistulas include:

  • Non-healing chronic wound
  • Foul smelling anal discharge
  • Pus leaking from an opening around the anus
  • Irritated skin around the anus
  • Fevers, chills, and fatigue

What Causes Anal Fistulas?


Anal fistulas are typically caused by clogged anal glands that lead to infections and anal abscesses. But they can also be caused by trauma, chronic conditions like Crohn’s disease, infection of an anal fissure, sexually-transmitted infections or tuberculosis.

Causes of an anal fistula include:



A persistent anal fistula that isn’t treated properly, can lead to recurrent abscesses or the development of additional fistula branches with more perianal wounds. Some complications include:



Though not all anal fistulas can be prevented, these lifestyle changes may help lower your risk and promote overall health.

  • Eat a healthy diet high in fiber, which will help keep your digestive system functioning well and bowel movements easier
  • Keep the anal area clean and dry, and maintain hygiene after bowel movements
  • Maintain healthy bowel habits, and avoid straining and prolonged sitting on the toilet while using the restroom
  • Exercise
  • Drink plenty of water
Get Care

Trust NewYork-Presbyterian for Anal Fistula Care

Our colorectal surgeons have extensive experience treating colon and rectal diseases, including anal fistulas, from the simplest to the most complex. Fistula care is complicated and requires knowledge of the special anatomy in this area to drain the infection and cure the fistula while maintaining bowel control. Your doctor will choose the surgical treatment that is most appropriate for your care.