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Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Bhupinder Anand, MD

The anal canal is the last part of the colon or large intestine as it exits the body. It is very short, approximately 1-2 inches long and has two circular muscles that help control the passage of bowel movements. The internal anal sphincter is not a voluntary muscle, and it is always contracted to help prevent stool from leaking out. The external anal sphincter is a voluntary muscle.

• An anal fissure describes a tear in the skin lining of the anal canal, or trauma to the anus and anal canal. The trauma usually occurs individual strains during a bowel movement or with constipation. Often, the individual may remember the exact bowel movement during which their pain began.
• An acute anal fissure describes a tear in the superficial layer of skin.
• A chronic anal fissure develops over time if the superficial tear does not heal. The tear extends deeper into the mucosa or tissue that lines the muscle of the internal anal sphincter.

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