Anal stenosis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 30, 2016
StartDiseasesAnal stenosis

Anal stenosis is a rare medical disorder that occurs when the patient's anal canal becomes too narrow to function properly. It can be caused by a wide variety of medical problems with the method of treating the disorder varying based on the cause. It is also called anal stricture.


Definition & Facts

Stenosis refers to an entire family of disorders that are characterized by the unhealthy narrowing of a tube inside the body. Anal stenosis refers to the constriction of the anal canal. That tube is located immediately behind the anal sphincter, and it allows waste to pass out of the body.

Intestinal obstructions can lead to serious medical problems very quickly, since they prevent the healthy passage of waste. This is especially true of anal stenosis because it is more difficult to treat than many other obstructions. Fortunately, the problem is rare and usually occurs immediately after a medical treatment, so it is easy for doctors to discover and treat the problem.

Symptoms & Complaints

The primary symptom of anal stenosis is difficulty defecating, which can escalate into a complete inability to defecate in some cases. Patients who retain the ability to defecate usually experience intensely painful bowel movements. Rectal bleeding is also a common problem.

If the disorder is not treated, it can eventually cause a full bowel obstruction. The obstruction will cause additional pain, but it can also lead to abdominal distension and vomiting. The vomit will sometimes include feces (fecal vomiting). These symptoms will persist until the anal stenosis is treated. A minority of bowel obstructions will prove to be fatal, but the vast majority of them will not.


A minority of anal stenosis patients are born with the disorder or after extended periods of anal inflammation, but the majority of cases occur after a surgery in the area of the anus or rectum. It most commonly occurs after the surgical treatment of inflamed hemorrhoids, but it also commonly occurs after the removal of skin tags and after anal dilation procedures.

These procedures cause scar tissue to accumulate inside the anal canal, which reduces the amount of space through which waste can safely flow. Since scar tissue is less flexible than other types of tissue in the human body, these surgeries are more likely to cause anal stenosis than inflammation or other complaints that can lead to narrowing. In addition to the cases that arise in the aftermath of surgery, some patients experience anal stenosis after taking laxatives for long periods of time.

Infections, especially those that occur in the lower gastrointestinal tract or in organs that are located near the anal canal, can also lead to the rare cases of inflammation that are sufficient to cause anal stenosis. A small number of sexually transmitted diseases can have a similar impact on the anal canal, although they make up a small minority of the reported cases of anal stenosis in the general population.

Diagnosis & Tests

Diagnosing anal stenosis is usually a straightforward process. The process begins when the patient reports difficult or painful bowel movements. Some patients also report rectal bleeding at this stage, but many of them seek medical attention before that symptom appears.

Doctors usually begin by checking for other, more common disorders that can also cause constipation, but some of them will skip that stage if the patient has already been taking laxatives for a reasonable length of time. The doctor will inquire about the patient's medical history and family history and if the patient has had previous surgeries for hemorrhoids or other diseases of the anal region, since these significantly increase the risk of anal stenosis.

The main diagnostic test for anal stenosis is a physical examination which involves the physician visually inspecting the anal area as well as performing a digital rectal examination. The doctor may apply an anesthetic in some cases. If the physician detects signs of anal stenosis, they will perform additional tests to find the cause or causes of the problem.

Treatment & Therapy

Doctors can use several different techniques to treat anal stenosis. If the disorder is the result of another disease, treating the cause is often enough to treat the stenosis. If doing so is impossible, there are treatments available to mitigate symptoms. Laxatives can be used to ease the passage of waste through the anal canal. While this does not widen the passage, it does reduce constipation, a significant symptom of the disorder.

If that is insufficient, surgical options are available. Most of the surgeries work by either placing incisions in the scar tissue to reduce it in size or by removing the scar tissue that is clogging the anal canal.

These surgeries are a tool of last resort due to the risk that is inherent to surgical procedures, but they can cure most cases of anal stenosis. Congenital cases are an exception, and they are usually treated with anal dilation. The procedure gradually expands the anal canal, which provides more space for waste to pass through the body.

Prevention & Prophylaxis

Congenital anal stenosis cannot be prevented, but it is sometimes possible to prevent other cases. The vast majority of patients who suffer from anal stenosis do so after hemorrhoid surgery.

Actions that can prevent inflamed hemorrhoids, including a high-fiber diet, regular exercise, consuming sufficient fluids, and avoiding straining while defecating can all reduce the odds of anal stenosis by reducing the odds of having to have that surgery. Avoiding excessive use of laxatives will also reduce the odds of anal stenosis, as can avoiding exposure to infectious diseases.