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How common is fistula after abscess

Published 13 March 2026 ·Last reviewed 13 March 2026 by the editorial team ·How we create our content

At a glance

One of the first questions people ask after having a perianal abscess drained is: “Will I get a fistula?” The honest answer is that there is a meaningful chance — roughly 30 to 50 percent — but it is not inevitable. Understanding the odds and what to watch for helps manage the uncertainty.

The numbers

Published studies report fistula formation rates after perianal abscess ranging from approximately 26 to 50 percent, depending on the study. The variation reflects differences in study populations, follow-up duration, and how fistulas are defined and detected.

The practical takeaway: roughly one in three to one in two people who have a perianal abscess will develop a fistula. The remaining people will heal completely.

Factors that affect the risk

Higher risk

  • Abscess type: abscesses that involve the sphincter muscles (intersphincteric, transsphincteric) have higher fistula rates
  • Abscess location: deeper abscesses that sit further from the skin surface
  • Recurrent abscesses: a second or third abscess in the same area increases the likelihood
  • Associated conditions: Crohn’s disease significantly increases fistula risk
  • Spontaneous drainage: abscesses that burst on their own rather than being surgically drained may have higher fistula rates (though data is mixed)

Lower risk

  • Simple perianal abscess: small, superficial abscesses have lower fistula rates
  • Prompt surgical drainage: controlled drainage may allow better assessment and potentially lower fistula rates
  • No underlying conditions: absence of IBD or other predisposing conditions

What to watch for

After abscess drainage, signs that a fistula may be developing:

  • Persistent drainage from the wound site beyond the expected healing time
  • Recurrent swelling in the same area
  • A small opening on the skin that continues to ooze
  • Intermittent pain that comes and goes in a cyclical pattern

The follow-up plan

Most surgeons schedule a follow-up appointment four to six weeks after abscess drainage. At this appointment:

  • The wound is assessed for healing
  • Any ongoing drainage is evaluated
  • The possibility of fistula formation is discussed
  • Further investigation (examination under anaesthesia or MRI) may be recommended if there are signs of a developing fistula

If your abscess has healed completely by this appointment — no drainage, no swelling, no pain — the risk of fistula development decreases significantly, though ongoing awareness is sensible.

Managing the uncertainty

The waiting period after an abscess — watching for signs of a fistula while hoping the area simply heals — is stressful. People describe it as a period of hypervigilance.

What helps:

  • Understanding the numbers — knowing the risk is meaningful but not certain
  • Following up as scheduled rather than waiting and wondering
  • Knowing what to watch for — specific signs rather than vague anxiety
  • Accepting that fistula formation, if it happens, is treatable

Common questions

What percentage of abscesses lead to fistulas?

Published studies estimate that approximately 30 to 50 percent of perianal abscesses lead to fistula formation. This means that roughly half of people who have a perianal abscess will develop a fistula, while the other half will heal completely. These numbers vary by study and depend on factors like abscess location and whether the infected gland is addressed at the time of drainage.

Does the type of abscess affect fistula risk?

Yes. Intersphincteric and transsphincteric abscesses (those that involve the sphincter muscles) have higher rates of fistula formation than simple perianal abscesses. Deeper or more complex abscesses are generally associated with higher fistula risk.

Can anything reduce the risk of fistula formation?

Some surgical techniques attempt to identify and address the internal opening (the infected gland) at the time of abscess drainage. This may reduce fistula rates, though the evidence is still developing. Prompt treatment of the abscess, rather than allowing it to drain spontaneously, may also help.

How long should I watch for fistula development after an abscess?

Most fistulas become apparent within the first few months after an abscess. Follow-up with your surgeon at four to six weeks is typical. If at that point the area is fully healed with no ongoing drainage, the risk of fistula decreases significantly. However, some fistulas declare themselves months later.

When to seek care Heavy bleeding or feeling faint? Get emergency help now. Emergency: 911

Not sure how urgent it is? Get help today.

  1. Emergency

    Heavy bleeding, black tarry stools, feeling faint, severe pain or trouble breathing.

    Call 911 or go to the ER.

  2. Today

    Fever, pain getting worse, a hot swollen lump, or trouble passing urine.

    Call your doctor or go to urgent care.

  3. Soon

    Bleeding or bowel changes nobody has checked, or anything lasting 3 weeks.

    Book a doctor’s appointment.

Feeling overwhelmed? Call or text 988, any time.

See all the signs

For this topic, get medical advice if you notice:

  • Increasing pain, swelling, or redness near the anus
  • Fever or chills
  • Pus or foul-smelling discharge
  • New or worsening symptoms after surgery

Recording how you feel is not the same as being checked. These are the signs that need a doctor’s attention.

Call 911 or go to the emergency room now if you have:

  • bleeding that will not stop, a lot of blood (the toilet water turns red, or you pass large clots), or any bleeding with feeling faint or dizzy
  • fainting, a racing heart or trouble breathing
  • confusion or slurred speech, extreme shivering, no urine in a day, or blotchy skin
  • sudden severe belly pain, or a swollen, hard belly with vomiting or not passing stool or gas
  • you cannot pass urine at all, or your bladder feels full and painful and you can’t empty it
  • redness, swelling or severe pain spreading quickly around your anus, genitals or groin, especially with a fever or feeling very ill
  • a fever with a painful swelling near your anus if you have diabetes or a weakened immune system (for example, from chemotherapy or transplant medicines)
  • black, tarry stools

Call your doctor or go to urgent care today (or the ER if you can’t be seen today) if you have:

  • a temperature of 100.4°F (38°C) or higher, chills, vomiting, or feeling generally unwell
  • pain that is getting worse over days, or severe pain that stops you sitting or sleeping
  • a hot, swollen or very tender lump near your anus or at the top of the crease between your buttocks, or foul-smelling discharge
  • trouble urinating
  • bleeding that is getting heavier or more frequent, or blood mixed into your stool
  • feeling much more tired than usual, looking pale, or getting out of breath more easily than you used to
  • not passing stool for several days, or new belly pain

Make an appointment with your doctor if:

  • you have never had these symptoms checked by a doctor or nurse — whatever your age
  • you have had rectal bleeding for more than 3 weeks
  • your bowel movements have been looser, thinner or more frequent than usual for 3 weeks or more, or you have lost weight without trying
  • symptoms have not settled after a week or so, or keep coming back
  • you notice a new lump near your anus, between your buttocks or in your belly, or an itch or discharge that does not clear
  • you have new leakage or trouble controlling your bowels
  • you are 45 or over, or have a family history of bowel cancer or inflammatory bowel disease, and any of these symptoms are new for you

If you are unsure, it is always reasonable to ask. If things feel overwhelming, call or text 988 (Suicide & Crisis Lifeline) or chat at 988lifeline.org, any time. If you don’t feel safe, call 911.

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Related symptoms

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When an abscess becomes a fistula

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From abscess to fistula: a pattern

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