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Conditions/Anal Fistula/Chapter

Detailed chapter

What Causes an Anal Fistula?

Abscess, Crohn’s, and less common triggers

Most anal fistulas start when a perianal gland infection becomes an abscess that drains to the skin, leaving a persistent track. Crohn’s disease, trauma, radiation, tuberculosis, and rarely tumors can also cause fistulas.

Causes · abscess to tunnel · English labels below

Key points

  • Anorectal abscess (most common)
    Tap for details · key note inside

    Blocked anal glands → abscess → drainage leaves an open channel. Recurrent swelling at the same site is a strong fistula clue.

    • Abscess → drainage → persistent track
    • Recurrent swelling
    • Antibiotics alone rarely cure the tunnel
  • Crohn’s and inflammation
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    Perianal fistulas are often complex and recurrent. Medical therapy plus drainage/seton is the foundation—not aggressive lay-open for everyone.

  • Other causes
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    Prior surgery, radiation, hidradenitis, tuberculosis, or malignancy can mimic or cause fistulas. Atypical features need extra evaluation.

  • Risk amplifiers
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    Diabetes, immunosuppression, smoking, and chronic diarrhea raise both fistula risk and recurrence after surgery.

This page is for education. It is not medical advice and does not replace a visit with your physician.

Medical editor: Assoc. Prof. Cengiz Dibekoğlu, MD · Last medically reviewed: August 2026 · English patient-education chapter.