At a glance
Not all anal fissures are the same. An acute fissure is a recent tear that has the potential to heal on its own with appropriate care. A chronic fissure is one that has persisted — typically beyond six to eight weeks — and has developed features that make spontaneous healing less likely. Understanding the difference helps you and your doctor choose the right treatment approach.
Acute fissure
What it is
An acute fissure is a fresh tear in the lining of the anal canal. It is essentially a small wound that, under the right conditions, can heal like any other wound.
How it develops
Most acute fissures are caused by:
- A hard or large bowel movement
- Constipation and straining
- Diarrhoea (which can irritate the anal lining)
- Childbirth
- Trauma to the area
What it looks and feels like
- A fresh, clean-edged tear — if visible, it looks like a shallow cut
- Sharp pain during bowel movements — often described as a tearing or cutting sensation
- Bleeding — typically bright red, small amounts on toilet paper
- Pain that may be intense but relatively brief — minutes to an hour after a bowel movement
- No sentinel pile or fibrotic edges — the tissue around the tear looks normal
Treatment
Most acute fissures heal within four to six weeks with conservative management:
- Dietary changes to produce soft stools
- Increased fibre and water intake
- Stool softeners
- Sitz baths
- Gentle hygiene
The success rate of conservative management for acute fissures is high — approximately 80 to 90 per cent heal without the need for topical treatments or procedures.
Chronic fissure
What it is
A chronic fissure is a fissure that has not healed despite adequate time and conservative management. It has developed structural changes that make it resistant to simple healing.
How it develops
An acute fissure becomes chronic when the cycle of spasm, reduced blood flow, and re-tearing is not broken. The internal sphincter remains hypertonic (too tight), blood flow to the wound remains insufficient, and the wound cannot heal. Over weeks, the tissue at the edges changes.
What it looks and feels like
- Thickened, fibrotic edges — the tear is no longer clean-edged; the margins are raised and firm
- A sentinel pile — a small tag of skin at the distal (outer) edge of the fissure
- Visible internal sphincter fibres — at the base of the fissure, the muscle fibres may be visible
- A hypertrophied anal papilla — a small fibrous polyp at the proximal (inner) edge
- Pain patterns may differ — less sharp tearing pain, more deep spasm-related pain that lasts longer
- The fissure does not close between bowel movements — it is a persistent wound
Treatment
Chronic fissures typically require more than conservative measures alone:
- Topical treatments (GTN or diltiazem) — relax the sphincter to improve blood flow. Success rate approximately 50 to 60 per cent.
- Botox injection — temporarily paralyses the sphincter. Success rate approximately 60 to 70 per cent.
- Fissurectomy with botox — removes the chronic tissue and relaxes the sphincter. Success rate approximately 70 to 85 per cent.
- LIS (lateral internal sphincterotomy) — permanently relaxes part of the sphincter. Success rate approximately 90 to 95 per cent, but with a small risk of incontinence.
Why the distinction matters
The treatment approach is different. An acute fissure responds well to dietary changes and sitz baths. Applying the same approach to a chronic fissure may result in months of unnecessary suffering when more effective treatments are available.
Conversely, jumping to surgery for an acute fissure is usually unnecessary — most heal on their own with time.
The important takeaway: if your fissure has not improved significantly after six to eight weeks of consistent conservative management, discuss whether it may have become chronic and whether escalation is appropriate.