Why is my Anus Tightening? Understanding Anal Stenosis

If it feels like your anus is tightening, it is possible that you have anal stenosis. However, other conditions can present with similar symptoms, so this article will cover the most important questions around anal stenosis to help you understand whether this is the problem.

Anal stenosis is the narrowing of the anal canal, which is responsible for the feeling of having a tight anus. Understandably, this constriction can mean you have difficulty passing stools, leading to straining on the toilet and anal fissures.

During bowel movements, it is natural for the muscles to expand and contract, which aids in the movement of stools through the anal passage. However, when anal stricture occurs, the muscles become too narrow to allow easy passage of fecal matter.

Understanding and treating anal stenosis requires examination of the probable causes. There are many reasons the anal passage can narrow, but some are more common than others.

The formation of scar tissue is the most common cause of anal stenosis. It usually happens after an operation in the area. For example, the removal of hemorrhoids or skin tags requires incisions around the anal passage or inside the anal canal. This can lead to what is known as ‘circular scarring’. The scar tissue is found just under the skin of the anal margin, and as scar tissue is not as flexible as normal tissue, it will not stretch enough to allow comfortable or complete passage of stools – especially larger ones.  

Radiation therapy can also lead to scar tissue in the pelvic region, which is why it is a common cause of vaginal stenosis. The same goes for anal radiation, which can also cause vaginal issues.

Sphincters are rings of muscle surrounding and guarding the opening or closing of a tube, and the anus has two of them: one is internal and the other external. The internal sphincter (which is inside the external sphincter) cannot be voluntarily controlled, while the external sphincter can. The sphincters act as seals that prevent stools from passing at the wrong time, and you can voluntarily contract the external sphincter if you can’t use the toilet when you have the urge.

Sometimes internal sphincter spasms occur because of anal fissures, which are tears in the anal tissues that cause sharp, stinging pain and bleeding. Hard or bulky stools, or constipation and straining can cause fissures, which can be considered chronic when they don’t heal for extended periods. Each bowel movement can prevent healing or cause a new one. The fissures can cause involuntary spasms, which over time can lead to rectal stenosis.

Having diarrhea on a regular basis, or constantly over time, means that the anal passage isn’t functioning normally. It does not need to stretch (dilate) and contract in order to pass firm stools, which leads to a loss of ability to dilate. This problem is commonly seen in those with autoimmune or inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease, which is why there is sometimes a link between those conditions and anal stricture.

Sepsis is a very serious blood infection resulting from a systemic response to local infection, and it is possible to develop anorectal sepsis for various reasons. Sepsis can compromise the vital organs of the human body, and should be treated immediately in hospital. Sepsis symptoms include hyperthermia, tachycardia, tachypnea, hypotension and altered mental status.

Although much more rare, rectal stenosis can result from a parasitic infection caused by the amoeba Entamoeba histolytica. It is only likely if you have visited a developing countries and come into contact with water containing human feces.

• Congenital deformity
• Trauma in the area
• Rectal infection
• Sexually transmitted diseases
• Intestinal malabsorption
• Weak blood vessels
• Age-related atrophy
• Age-related Alzheimer’s or senility (thus taking constipating medications and laxatives)

Again, the above causes are not the original reason for anal stenosis: it is always the scar tissue they cause that results in stenosis.

Anal stricture symptoms are not always exactly the same, but there are some general signs. For example, constipation is inevitable because of the difficulty in passing stools. Anal stenosis symptoms may also include:

• Rectal bleeding
• Blood in the stools
• Abdominal pain
• Abdominal bloating
• Pain when passing stools
• Stool leakage
• Small (pellet-like) or thin stools

For those with Crohn’s disease, there is an important distinction to make: one that may require the discernment of an experienced medical health practitioner. Crohn’s disease is an inflammatory bowel disease that is often linked to anal stenosis. It can cause anal stenosis, but can it can also lead to misdiagnosis since the symptoms of Crohn’s disease sometimes mimic rectal stenosis symptoms.

An anal stenosis diagnosis could be classified as mild, moderate, or severe. If you only have a mild or moderate case, it should be possible to insert an anal dilator. This is something your physician may do as part of an assessment. You will need a physical examination to assess the anal passage and skin, and your physician may perform a digital rectal test. If the examination is too painful, they may use local anesthetic. They will also discuss and assess your recurrent symptoms.

Another possibility is that your Doctor may perform an anorectal manometry. This is a test to check anal musculature tone. It also measures the sensation and reflexes in the rectum. The test consists of a little balloon, which is fixed to a tool resembling a catheter. This tool is connected to a machine that measures the pressure levels. The tool will be placed inside the rectum and inflated, and the machine will record the measurements.

Anal stenosis does not have to be a burden for the rest of your life. However, since many of the symptoms can create a ‘vicious cycle’ effect, it may not go away without some level of treatment. Treatments are considered to be generally effective, but it is better not to wait until further complications arise. Look out for our article on treatment options for anal stenosis, which gives helpful insights to help you heal from this testing condition.

Anal dilatation is performed to prevent the anal opening from becoming smaller and in turn increasing opening size to relive pain. Anal dilators come in various sizes and slowly stretch the anus. They are needed following your rectal surgery or resulting from a diagnosis after a rectal examination. Your surgeon/doctor will explain how often and for how long you need to use rectal dilators. This can range from a few weeks to months.

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Resources

Drgreene.com/qa-articles/anal-stenosis-anorectal-malformations

Ncbi.nlm.nih.gov/pmc/articles/PMC7063846/

Tgh.org/institutes-and-services/conditions/anal-stenosis