An anal fissure is a tear in the mucosal lining of the anal canal, most commonly due to trauma from defecation. It can be classified according to its duration:
- Acute – present for <6 weeks
- Chronic – present for >6 weeks
Anal fissures can also be categorised by whether they are primary (no underlying disease), or secondary (underlying disease e.g inflammatory bowel disease).
Anal fissures are usually caused by inflammation or trauma to the anal canal. The major risk factors include:
- Inflammatory bowel disease
- Chronic diarrhoea
The most common presenting feature of an anal fissure is intense pain post-defecation, which can last several hours. Pain can be far out of proportion to the size of the fissure. Other associated symptoms may include bleeding (commonly bright red blood on wiping) and itching, both post-defecation.
On examination, fissures can be visible and / or palpable (albeit very painfully) on digital rectal examination. Most fissures present in the posterior midline (90% cases); anterior fissures are more likely to in females or if an underlying cause is present*.
Often patients will refuse a digital rectal examination and examination under anaesthesia may be necessary for diagnosis. Fissures within the anal canal can usually be identified upon proctoscopy.
*Multiple fissures or anteriorly located fissures are more likely to be due to an underlying cause and require further investigations (if no known cause is apparent)
The medical management of an anal fissure involves reducing risk factors and providing adequate analgesia.
Measures such as increasing fibre in the diet and fluid intake will help. Stool softening laxatives (such as Movicol or Lactulose) can be trialled if there is no change in stool following initial conservative management.
If patients are still symptomatic, the next line of management is GTN cream. This increases the blood supply to the region and relaxes the internal anal sphincter, putting less pressure on the fissure, promoting healing and reducing pain.
Surgical therapy is reserved for chronic fissures where medical management has failed to resolve the symptoms. A lateral sphincterotomy is usually performed.
Recurrence of anal fissures post-surgery is between 1-5%, but studies have shown that the majority of these recurrence patients are those with an underlying predisposition to the condition.