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