What Is Anal Stenosis?
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Anal Stenosis - Causes, Symptoms, and Treatment.

Published on Oct 31, 2022 and last reviewed on Jul 26, 2023   -  4 min read


Anal stenosis is narrowing of the anal sphincter and difficulty in passing stool. The causes, symptoms, and treatment are explained in the article.


Anal stenosis is the narrowing of the anal canal, thus causing difficulty in passing stool. It is also known as an anal stricture. Ananl stenosis occurs due to the narrowing of the muscles, which leads to contraction and expansion for movement of the stool. The cause of this narrowing can be congenital, malformation, venereal disease, or rectal infection. Symptoms may include pain during bowel movements, constipation, or bright red blood after the passing of stool.

What Is Anal Sphincter?

The anal sphincter is part of the body that maintains a closed seal that can be opened to remove body waste. The anal sphincter is strong enough to restrict the passage of any fecal material but at the same time sensitive enough to differentiate between liquid, gas, and solid.

Anal sphincter muscles are of two types that are internal and external anal sphincter.

  • The internal anal sphincter is a thin white muscle wrapped around the anal canal. It contracts during rest and relaxes. It also prevents small amounts of liquid and gas from escaping involuntarily. The internal anal sphincter is an involuntary smooth muscle as it can not be controlled mentally.
  • The external anal sphincter is a thick, red muscle that is voluntary in nature. It is wrapped around the internal sphincter. It contracts/squeezes when a person feels the urge to go to the bathroom but can not go. As it is voluntary in nature, it can be controlled mentally.

How Does Food Waste Pass Out?

The food waste gets accumulated in the rectum gradually. The rectum is a flexible muscle pouch that is the last part of the large intestine. When sufficient waste is collected, there is an urge to go to the bathroom. Once the person sits on the toilet seat, the anal sphincter gets released and allows the anal canal to empty. When the waste is released from the canal, the anal sphincter restricts and closes until the process has to be performed again.

What Causes Anal Stenosis?

Narrowing of the anal sphincter can be due to many things, such as:

What Are the Symptoms of Anal Stenosis?

The symptoms of anal stenosis vary depending on its severity.

The symptoms observed are:

  • Painful bowel movements.

  • Constipation: difficulty in passing a normal stool.

  • Stools were removed in the form of small pellets.

  • Rectal bleeding: bright red blood seen in the toilet after passing out stool.

Treatment of Anal Stenosis?

The best treatment for anal stenosis is prevention from occurring. Some preventive measures are:

  • Use of stool softeners or emollient laxatives, which will add moisture to the stool.

  • Intake of more fiber supplements in the diet, as it facilitates easy passing of stool.

  • Sphincterotomy: procedure of cutting the anal sphincter muscle to open the anal canal.

If the condition still occurs, the following treatment modalities can be performed:

  • Anoplasty is a surgical procedure to relieve stenosis. The anus is reconstructed with this procedure.


  1. General anesthesia is administered to the patient.

  2. The narrow, stricture anus is enlarged and stretched.

  3. Skin flaps are used for reconstructing the anus.

  4. If any fistula is present, it is closed surgically.

  5. The anus restores its normal functioning after the treatment.


  1. Dehiscence: After the anoplasty, there can be a breakdown of the entire rectal repair, which is known as dehiscence. This can be due to excessive tension or ischemia.

  2. Strictures: Pressure due to surrounding muscles, tension, and ischemia can develop strictures in the region of anoplasty.

  3. Mucosal prolapse: After anoplasty, the mucosa can prolapse in the perineum and cause irritation at the site. It can also cause staining of underwear due to excess mucus secretion.

Precautions After the Surgery:

  • Avoid sitting directly on the surgical area, which is the anus.

  • Proper diet intake with good fiber content.

  • Avoid lifting heavy weights, especially more than 20 lbs, at least for ten days.

  • Drinking plenty of water, at least eight glasses in a day.

  • Before consuming blood thinners or aspirin, the doctor should be consulted.

Which Disease Is Similar to Anal Stenosis?

Perianal Crohn’s Disease: It is an autoimmune disease in which there is inflammation around the anus. These conditions can lead to fissures, skin tags, fistulas, and abscesses around the anus.

Symptoms resemble anal stenosis as they are:

  • Pain in bowel movements.

  • Itching around the anus.

  • Pus discharge in the cases of abscesses.

  • Bleeding from the rectum.

  • Bowel inconsistency and constipation.


Anal stenosis is the narrowing of the anal canal due to constriction of its muscles. This can be due to different reasons such as overuse of laxatives, sepsis, sexually transmitted diseases, or surgical complications. The symptoms include difficulty in passing stools and pain in bowel movements. There can also be traces of blood in the toilet after passing out stool. The treatment includes preventive measures and surgical procedures. The surgery performed to cure stenosis is anal reconstruction with the help of skin flaps.

Last reviewed at:
26 Jul 2023  -  4 min read




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