An anal fissure is a natural crack or tears in the skin of the anal canal. Anal fissures may be noticed by bright red anal bleeding on the toilet paper, sometimes in the toilet. If acute they may cause severe periodic pain after defecation but with chronic fissures pain intensity is often less. Anal fissures usually extend from the anal opening and are usually located posteriorly in the midline, probably because of the relatively unsupported nature of the anal wall in that location. Fissure depth may be superficial or sometimes down to the underlying sphincter muscle.
Most anal fissures are caused by stretching of the anal mucosa beyond its capability. For example, anal fissures are common in women after childbirth, after difficult bowel movements, and in infants following constipation.
Superficial or shallow anal fissures look much like a paper cut, and may be hard to detect upon visual inspection, they will generally self-heal within a couple of weeks. However, some anal fissures become chronic and deep and will not heal. The most common cause of non-healing is spasm of the internal anal sphincter muscle which results in impaired blood supply to the anal mucosa. The result is a non-healing ulcer, which may become infected by fecal bacteria.
For adults, the following may help prevent anal fissure:
- Avoiding straining when defecating. This includes treating and preventing constipation by eating food rich in dietary fiber, drinking enough water, and avoiding constipating agents such as caffeine. Similarly, prompt treatment of diarrhea may reduce anal strain.
- Careful anal hygiene after defecation, including using soft toilet paper and/or cleaning with water.
- In infants, frequent nappy/diaper change can prevent anal fissure. As constipation can be a cause, making sure the infant is drinking enough fluids (i.e. breast milk) may thus help avoid fissures. In infants, once an anal fissure has occurred, addressing underlying causes is usually enough to ensure healing occurs.