Why Your Anal Fissure Won’t Heal (And What Finally Fixes It)

Patients with a chronic anal fissure are often frustrated by the time they reach a surgeon. They have been told to eat more fibre, they have done it. They have used ointments for months. The pain keeps coming back, and they have started to wonder whether something is being missed.

Usually nothing is being missed. What is happening is a self-sustaining cycle that dietary change alone cannot break once it is established.

The cycle, step by step

It begins simply enough. A hard stool causes a small tear in the lining of the anal canal, most often in the midline at the back where the blood supply is naturally poorest.

The tear hurts intensely, because this area has one of the densest concentrations of pain nerve endings in the body. The pain triggers the internal anal sphincter to go into spasm — an involuntary reflex you cannot consciously control.

That spasm does two things. It hurts in its own right, producing the deep burning ache that continues for hours after passing stool. And, crucially, a contracted sphincter compresses the small vessels supplying the anal lining, reducing blood flow to exactly the area that needs to heal.

A wound with poor blood supply cannot heal. So the tear persists. The next stool tears it again. And so on.

Acute versus chronic — and why six weeks matters

A fissure present for less than six weeks is called acute. It is a fresh, shallow tear, and with proper treatment — genuinely high fibre, adequate water, stool softeners, warm sitz baths and a sphincter-relaxing ointment — the large majority heal.

Beyond six to eight weeks it becomes chronic, and the appearance changes. The edges become fibrous and indurated. A sentinel skin tag forms at the outer end and a hypertrophied papilla at the inner end. The base may show exposed sphincter fibres.

A chronic fissure with these features rarely heals on medical treatment alone, no matter how disciplined the patient is. Continuing ointments indefinitely at that stage is not persistence; it is delay.

What proper medical treatment looks like

Before concluding that medical treatment has failed, it is worth checking that it was actually done properly. It frequently was not.

• Isabgol one to two teaspoons daily in a full glass of water, taken consistently rather than occasionally
• Two to three litres of water a day
• A stool softener taken regularly for the full course, not stopped as soon as pain eases
• Warm sitz baths for ten minutes, two to three times daily and after each bowel movement — the warmth genuinely relaxes the sphincter and is not merely soothing
• A sphincter-relaxing ointment — glyceryl trinitrate or diltiazem — applied correctly into the anal canal, not merely smeared outside, twice daily for six to eight weeks
• Avoiding the temptation to postpone bowel movements out of fear, which hardens the stool further

Botulinum toxin: a chemical pause

Injecting botulinum toxin into the internal sphincter relaxes it for around three months, breaking the spasm cycle chemically and giving the fissure a window to heal.

Healing rates are better than with ointments but lower than with surgery, and fissures can recur once the effect wears off. Its main value is in patients where permanent sphincter division carries too much risk — some women with anterior fissures, or those with previous obstetric injury.

The operation that resolves it

Lateral internal sphincterotomy is a short day-care procedure and has been the standard curative treatment for chronic fissure for decades. Cure rates exceed ninety-five percent.

The principle follows directly from the mechanism. A small, carefully measured portion of the internal sphincter is divided — laterally, away from the fissure itself. This permanently releases the spasm, blood flow to the area returns, and the fissure heals.

The most striking thing for patients is the speed. Most report that the characteristic tearing pain is simply gone from the very first bowel movement after surgery. What remains is mild soreness at the small lateral wound, a quite different and much milder sensation.

A laser variant achieves the same release with less bleeding and a smaller wound.

The question everyone should ask: what about continence?

This is the right concern, and it deserves a direct answer rather than reassurance.

The internal sphincter is the involuntary muscle that maintains resting tone. It is not the external sphincter — the voluntary muscle you use to hold on deliberately. Only a small, measured portion of the internal muscle is divided, calibrated to the length of the fissure.

A small percentage of patients notice temporary difficulty controlling flatus, which usually settles. Permanent incontinence to stool is rare after a properly measured sphincterotomy.

It is not, however, zero risk, and that is precisely why the procedure is avoided in higher-risk patients — women with anterior fissures, those with a history of difficult childbirth or obstetric tear, the elderly, and anyone with pre-existing continence problems. For those patients, botulinum toxin or a fissurectomy with advancement flap is used instead. If your surgeon does not raise this, ask.

Fissures that need investigating rather than operating

Not every fissure is a simple mechanical tear, and treating an atypical one as if it were is a mistake.

• Fissures located away from the midline, at the sides
• Multiple fissures at once
• Fissures with unusually broad, undermined or irregular edges
• Fissures accompanied by diarrhoea, weight loss, mouth ulcers or joint pains
• Fissures that fail to heal even after adequate surgery

Preventing the next one

The operation fixes the current fissure. It does not prevent a new one, and roughly the same habits that caused the first will cause another.

Continue fibre and fluids indefinitely rather than for six weeks. Do not postpone the urge. Keep toilet time short. If you are prone to constipation, keep isabgol as a permanent part of your routine rather than something you restart when trouble appears.