An anal fissure is an open sore (ulcer) or tear that occurs in the lining of the anal canal. The anal canal is the last part of the large intestine, located between the rectum, where stools are stored and anus (the opening through which stool passes out of the body). Anal fissures can occur at any age and have equal gender distribution. Mostly (85-90%) fissures develop in the posterior (back) midline of the anus with about 10-15% developing in the anterior (front) midline. A small number of patients may actually have fissures in both the front and the back locations. Fissures located elsewhere (off to the side) should raise doubt for other diseases and will require to be examined further.
Anal fissures develop in the specialized tissue that lines the anus and anal canal, known as anoderm. At a line just inside the anus the skin (dermis) of the internal buttocks changes to anoderm. Not like skin, anoderm has no sweat glands, hair or sebaceous (oil) glands and it contains a large quantity of sensory nerves that sense light touch and pain. (The large quantity of nerves explains why anal fissures are very painful.) The hairless, gland-less, extremely sensitive anoderm covers the entire length of the anal canal until it meets the distinguishing line for the rectum, called the dentate line.
The tear in the skin causes severe pain and bleeding during and after bowel movements. Occasionally, the fissure can be deep enough to expose the muscle tissue underneath.
An anal fissure usually isn’t a serious condition. It’s often seen in infants and young children since constipation is a common problem in these age groups.
In most cases, the tear heals on its own within four to six weeks. In cases where the fissures continue beyond eight weeks, it’s considered chronic.
Specific treatments can promote healing and help relieve discomfort, including stool softeners and topical pain relievers.