Anal fistula


Basic Information


A very small tube or tract that leads from the anal canal to the skin near the anal opening. Watery pus drains through this opening and causes irritation to the skin.

Frequent signs and symptoms

  • Constant or intermittent discharge.
  • Firm-tender lump.
  • Pain during or after bowel movement.
  • Discoloration of skin surrounding fistula.


  • Erosion of tissue because of spreading abscess.
  • Extension from infection from a tear in the anal canal lining.
  • May be found occasionally in association with trauma, rectal infection (including chlamydia), carcinoma and radiation therapy.

Risk increases with

  • Puncture wound in anal canal lining (e.g., from eggshell or fishbone) or injury from an enema tip.
  • Injection treatment for internal hemorrhoids.
  • Inflammatory bowel disease.
  • Acute appendicitis or diverticulitis.

Preventive measures

No particular preventive steps.

Expected outcomes

Surgical results usually excellent.

Possible complications

  • Constipation.
  • Fistula may recur if not completely excised by surgery.

Anal fistula treatment

General measures

  • Minor surgical procedure to excise fistula. Usually with local anesthetic (occasionally general anesthetic required).
  • Warm sitz baths after surgery to help relieve any discomfort.


  • Stool softeners may be prescribed to prevent constipation.
  • Antibiotics may be prescribed if infection present.


Resume work and normal activity as soon as possible.


Regular diet

Notify your physician if

You or a family member has any symptoms of an anal fistula.

Last updated 10 May 2016


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