What is an anal fissure?

An anal fissure is a split in the skin of the anal verge, the exit of the bowel from the body. They are sometimes caused by a bout of constipation or diarrhoea but can appear out of the blue. Fissures tend not to heal without special treatment.


Pain during and after having the bowels open is the main problem. People often mistake a fissure for haemorrhoids but haemorrhoids as a rule are not painful. Fissures will also result in some bleeding from the anus and itchiness (pruritus ani). A small lump may appear at both ends of the split.


The crux of treatment is to relax the inner anal muscle (the internal anal sphincter). The reason for this is the pain from the fissure results in spasm of this muscle which prevents the fissure from healing. The stool you pass needs to be soft so a high fibre diet and plenty of fluids will help. If the stool is still firm then a laxative such as Movicol or Normacol will help, 1-2 sachets a day.

GTN (Rectogesic) and Diltiazem (Anoheal) are the first line treatments. You apply a pea-sized lump of the ointment around the anus twice a day. The side effect of GTN may be a headache. If this happens, use less of the ointment. 10% of people develop skin sensitivity to diltiazem. This results in symptoms getting worse a few days after starting the cream so the best thing to do is stop using it and bring your clinic appointment forward so you can be reviewed.

Fissures that are resistant to creams can be treated by Botox injection. This can be done in the clinic or under a general anaesthetic. It results in a reversible relaxation of the anal muscles for about three months, which is usually long enough to allow the fissure to heal.

Surgery is reserved for fissures that are symptomatic despite the measures above. The lower half of the internal anal sphincter muscle is divided, “a subcutaneous internal anal sphincterotomy”. Whilst this is very effective (94% cure at 1 month), it is irreversible and has a 10% risk of you being less able to control gas from the rectum. In a man there is less of a problem. Control of gas is more of an issue in women as they have a smaller muscle bulk and previous childbirth can weaken the muscles too. Your Surgeon will go through all these options carefully with you and tailor your treatment to your individual circumstances and preferences.