Clinical features

The salient features of fissure in ano are:

• history of pain of defaecation - often first occurs during a period of constipation
• the passing of stools may cause sphincter spasm and acute pain during defaecation, which may persist for up to an hour
• patient may develop a fear of defaecation which in turn aggravates the constipation; even sitting may be avoided
• there is often fresh rectal bleeding at defaecation; the patient complains of 'bright red blood on the paper'

On examination:

• there is a longitudinal tear that nearly always occurs directly posteriorly and in the midline
• a sentinel pile may be seen if the anus is inspected with the buttocks gently parted; the sentinel pile is the torn, bunched-up strip of mucosa at the base of the fissure

The severity of the pain and muscle spasm may preclude digital examination and necessitate examination under general anaesthesia.