Fistula-in-Ano: What It Is, Why It Keeps Coming Back and When Surgery Is the Answer

An anal fistula is one of the conditions most reliably undertreated in Indian medicine — not because it is rare, but because it is uncomfortable to discuss, slow to deteriorate dramatically, and repeatedly managed with antibiotics that treat the infection without closing the track. The result is patients who have been living for years with a small opening near the anus that intermittently discharges pus or blood, who have had multiple courses of antibiotics, possibly one or two incision-and-drainage procedures for abscesses, and who have never been told clearly: a fistula requires surgery, antibiotics will not cure it, and the longer you wait, the more complex the surgery becomes.

What Is a Fistula-in-Ano?

An anal fistula is an abnormal tunnel — a tract lined with granulation tissue — connecting an internal opening inside the anal canal (almost always at an anal gland in the dentate line zone) with an external opening on the perianal skin. It is almost always the consequence of a perianal abscess: when an anal gland becomes infected and forms an abscess, and the abscess either spontaneously ruptures or is surgically drained, the track between the original gland and the skin surface may persist as a fistula rather than closing and healing. The internal gland remains infected, the external opening keeps discharging, and no amount of antibiotics closes the track because the source of the infection is not removed.

Types of Fistula and Why It Matters

Fistulas are classified by their relationship to the anal sphincter muscles — and this classification directly determines what surgery is appropriate:

• Intersphincteric fistula: The track passes between the internal and external sphincters, staying low. The most common type. Generally amenable to fistulotomy — laying open the track — with low risk to sphincter function.
• Transsphincteric fistula: The track crosses through a portion of the external sphincter. The higher the crossing, the more complex the surgery and the greater the risk to continence. Low transsphincteric fistulas can be laid open; high ones require sphincter-sparing approaches.
• Suprasphincteric fistula: Passes above the level of the puborectalis muscle. Uncommon, complex, requiring staged surgery.
• Extrasphincteric fistula: Passes outside the sphincter complex entirely. Rare, often secondary to Crohn's disease, pelvic sepsis, or iatrogenic injury.

The classification is determined by examination under anaesthesia (EUA) and, in complex cases, by MRI of the pelvis — which provides a detailed roadmap of the fistula track and its relationship to the sphincter before surgery begins.

Why a Fistula Will Not Heal Without Surgery

The internal opening of the fistula — in the anal gland at the dentate line — is the source of ongoing contamination. Every time stool passes through the anal canal, bacteria and faecal material enter the internal opening, travel through the fistula track, and discharge at the external opening. The track cannot close as long as this cycle continues. Antibiotics reduce the acute inflammation and discharge temporarily, but they do not remove the track or close the internal opening. When the antibiotic course ends, discharge resumes. This is why fistulas are said to "keep coming back" — they are not coming back; they never left.

Surgical Options: Matching the Procedure to the Fistula

Fistulotomy (Laying Open)

The classic and most effective operation for simple, low fistulas that involve minimal or no sphincter muscle. The entire fistula track is opened (laid open) to the skin surface and allowed to heal from the base by secondary intention. Highly effective with over 90% cure rates. The limitation is the amount of sphincter muscle it is safe to divide — for high fistulas, division of too much sphincter risks faecal incontinence.

Seton Placement

A seton is a thread (suture, silicone, or Teflon) passed through the fistula track and tied loosely (loose seton — for drainage and identification of the track) or progressively tightened over weeks (cutting seton — for gradual division of sphincter). Loose setons are used to drain complex fistulas, allow inflammation to settle, and prepare the tract for a later definitive procedure. Cutting setons progressively divide the sphincter slowly enough for fibrosis to form and maintain continence — useful for selected high transsphincteric fistulas.

LIFT Procedure (Ligation of the Intersphincteric Fistula Tract)

A sphincter-sparing technique performed in the intersphincteric plane — the space between the two sphincters. The fistula track is identified in this plane, ligated (tied off), and divided. The internal and external wounds are then closed. LIFT preserves both sphincters intact and avoids the continence risk of fistulotomy in high fistulas. Success rates of 60–80% in appropriate cases.

Advancement Flap

A flap of rectal mucosa is used to cover the internal opening of the fistula, closing it from the inside while the external track is curetted. Used for high, complex, or recurrent fistulas.

The Most Important Pre-Surgical Investigation: MRI of the Pelvis

For any fistula that is not clearly simple and superficial on clinical examination, an MRI of the pelvis with thin-cut coronal sequences is performed at Solo Clinic GI before planning surgery. MRI maps the full extent of the fistula track, identifies secondary extensions and horseshoe extensions, and precisely defines the sphincter anatomy — preventing surgical surprises and enabling the correct procedure to be chosen before the patient is on the operating table.

Frequently Asked Questions

Will a fistula heal on its own without surgery?

No. A true fistula-in-ano — with an established track, a patent internal opening, and an external opening — will not close spontaneously. Some very acute, very early post-abscess fistulas may close if the internal opening heals before a proper fistula track forms, but this is uncommon. Once a fistula track is established and draining, surgery is the only definitive treatment. Antibiotics can temporarily reduce discharge but will not cure the fistula.

Will fistula surgery affect my bowel control?

The risk of incontinence after fistula surgery depends on the type of fistula and the surgical approach. For simple low fistulas treated by fistulotomy, the continence risk is minimal — well under 5%. For high or complex fistulas, sphincter-sparing techniques (LIFT, advancement flap, or seton) are used specifically to avoid incontinence, with the tradeoff of somewhat lower initial cure rates. Dr. Rajesh discusses the specific risk for your fistula type — determined after clinical examination and MRI — before any surgical plan is agreed.

How long does fistula surgery take to heal?

For fistulotomy (laying open), wound healing by secondary intention takes 6–12 weeks depending on the length of the track. The wound needs regular dressing changes during this period. Most patients return to desk work within 1–2 weeks of surgery, though the wound continues healing. For LIFT or advancement flap procedures, the wounds are smaller and healing is faster, though close follow-up is needed to confirm the internal opening has remained closed.

I've had my perianal abscess drained twice. Do I now have a fistula?

Possibly — but not certainly. Approximately 50–60% of perianal abscesses result in a fistula after drainage. If the wound from your abscess drainage has not fully healed after 4–6 weeks, or if it closed and then started discharging again, a fistula is likely. If the wound healed completely and stayed healed, there may be no fistula. A clinical examination and, if needed, an MRI or examination under anaesthesia will give a definitive answer. See our article on perianal abscess and its link to fistula formation.

Can Crohn's disease cause anal fistulas?

Yes — perianal fistulas are a recognised extraintestinal manifestation of Crohn's disease, occurring in approximately 25–40% of Crohn's patients. Crohn's fistulas are typically more complex, more likely to be high, and more likely to recur after surgery. Their management involves close collaboration between a gastroenterologist (for medical management of the underlying Crohn's) and a colorectal surgeon — and is significantly different from the management of cryptoglandular (standard) fistulas. If you have known Crohn's disease and a perianal fistula, this must be disclosed at your consultation.

Perianal Discharge That Won't Heal? It's Almost Certainly a Fistula.

Dr. Rajesh Tandulwadkar assesses every anorectal fistula with clinical examination and MRI before planning surgery — the right procedure for your specific anatomy, the first time. Solo Clinic GI, Bund Garden Road, Pune.

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Medical Disclaimer: Fistula surgery carries procedure-specific risks including recurrence and, in complex cases, alteration in bowel function. This article is for informational purposes only. Consult Dr. Rajesh Tandulwadkar for advice specific to your fistula type, anatomy, and surgical history.