In short
An anal fissure is a tear in the lining of the anal canal. It causes a sharp, tearing pain during a bowel movement that can carry on for hours afterwards, often with a streak of bright red blood. It is the most painful of the common anorectal problems and one of the most treatable.
Why doesn't it heal by itself?
Because of a vicious circle. The tear hurts, the pain makes the internal sphincter muscle go into spasm, the spasm squeezes the small arteries that supply the area, and the reduced blood flow stops the tear healing. The next bowel movement reopens it.
This is the key to the whole condition: a chronic fissure is a blood-supply problem caused by muscle spasm, not simply a cut. It is also why creams that only soothe do not fix a chronic one.
Acute or chronic?
A fissure under six weeks old is acute, and most heal with fibre, water, warm sitz baths and something to keep stools soft.
Past six weeks it is chronic, usually with a visible skin tag at the outer end and exposed muscle fibres at the base. Chronic fissures rarely heal on conservative treatment alone.
What is tried before surgery
Topical medication that relaxes the sphincter — a nitrate or a calcium-channel blocker — breaks the spasm and lets blood back in. Given properly, for long enough, this heals a good proportion of chronic fissures. Headaches are a common side effect of the nitrates and are worth knowing about in advance.
Surgery, and the honest trade-off
The traditional operation, lateral internal sphincterotomy, divides a small part of the internal sphincter to release the spasm permanently. It has a very high healing rate. It also carries a small but real risk of affecting control of wind or, less commonly, stool.
That risk is why the sphincter is assessed carefully first, why the amount divided is tailored rather than standard, and why sphincter-sparing approaches — including laser techniques — are considered first for patients where continence is a particular concern.
The part people skip
A fissure is usually caused by a hard stool, and it will happen again if bowel habit does not change. The fibre, fluid and toilet-habit plan is not an afterthought — it is the part that decides whether you are back in a year.
See a doctor promptly if
- The pain is severe and constant rather than tied to bowel movements
- There is a discharge of pus, or a swelling that is hot to touch
- The fissure is off to the side rather than front or back — atypical fissures need investigating
- You also have diarrhoea, mouth ulcers or weight loss — inflammatory bowel disease can present this way
- It has not healed after six weeks of proper treatment
These are the symptoms that should not wait.
Common questions
- Why does the pain last for hours after I go?
- That is the sphincter spasm, not the tear itself. The muscle clamps down after the bowel movement and stays contracted, which is both the source of the lingering pain and the reason the fissure will not heal.
- Will surgery affect my control?
- Sphincterotomy carries a small risk to control of wind, and a smaller one to stool. It is not zero, and anyone who tells you it is, is not being straight with you. The risk is managed by assessing your sphincter first, tailoring how much is divided, and choosing a sphincter-sparing option where that risk matters most.
- Can a chronic fissure heal without surgery?
- Yes, a meaningful proportion do, with sphincter-relaxing medication used correctly and for long enough, alongside a real change in bowel habit. Surgery is for the ones that do not.
General information only. Anorectal symptoms overlap and only an examination can tell them apart — please do not use this page to diagnose yourself.