Anal sphincter function, anatomy, and complications

The anal sphincter is a group of muscles at the end of the rectum. The rectum is located in the last few inches of the large intestine (colon). The anal sphincter surrounds the anus and controls the release of stool, thereby maintaining incontinence. He has two muscles: the internal anal sphincter and the external anal sphincter.

If you have trouble holding in your stool or urine (or leak), have pain in your rectum, or experience pain during sex, your anal sphincter may be damaged.

This article describes the anatomy of the anal sphincter and its functions. You will also learn about symptoms that affect the anal sphincter and what can happen if the anal sphincter is injured.

Anatomy of the anal sphincter

The average adult rectum length is about 4.7 inches. At the bottom of the rectum is the anal sphincter.

The anal sphincter is two muscles.

• Internal anal sphincter: This is located inside the rectum.
• External anal sphincter: It goes around the outside of the end of the anal canal.

of pudendal nerve It is the main nerve in the pelvis. It tells the muscles that control the pelvic organs and reproductive organs to move.

One of the nerves’ jobs is to send messages to the branches to close the anal sphincter and prevent stool and urine from leaking.this is called anal sphincter innervation.

Function of the anal sphincter

of anal sphincter reflex This is the process that occurs when stool moving through the digestive tract relaxes the internal anal sphincter, which in turn causes the external anal sphincter to contract. This reaction is also called the defecation reflex.

The internal and external anal sphincters work together to cause defecation, but in different ways.

Loss of muscle control of the sphincter can result in fecal incontinence.

diseases and symptoms

There are several diseases, conditions, and injuries that can affect the anal sphincter. Symptoms for these conditions can vary, but in general, signs that you may have a problem with your anal sphincter include:

• pain and bleeding from the anus
• Problems with bowel and gas control
• Feeling of urgency to defecate
• anal secretions

anal stenosis

Although anal stenosis is not a common symptom, it may be associated with inflammatory bowel disease (IBD). It is more common in Crohn’s disease than ulcerative colitis.

In anal stenosis, the internal anal sphincter becomes narrow, making it difficult to defecate. Other symptoms include pain and bleeding.

Anal stenosis can occur after surgery, especially after removal of hemorrhoids, or in association with overuse of laxatives or infection.

This condition may be treated with stool softeners and fiber supplements. Surgery may also be required to correct the problem.

anismus

Anismus is a dysfunction of the pelvic floor muscles, including the external anal sphincter. This is caused by a problem with the way these muscles contract and relax during a bowel movement.

Symptoms of anismus include:

• Having bowel movements less than 3 times a week
• straining excessively to defecate
• hard and painful stools
• stomach pain and bloating
• anal pain
• Feeling like you haven’t finished defecating yet

Anismus is often treated with pelvic floor muscle exercises. Botulinum toxin injections are also effective.

anal fissure

An anal fissure is a tear in the lining of the anus. Anal fissures often extend into the internal anal sphincter. These are caused by overstretching of the anal canal and can occur when having a very hard or large bowel movement.

Symptoms of anal fissure include pain and a feeling of tearing when defecating. Bright red blood may stain the toilet or toilet paper. These symptoms usually occur with each bowel movement. It is not uncommon for the condition to become chronic, as the damage can worsen with each bowel movement.

Anal fissures can be treated with topical medications, drugs that relax the sphincter, or surgery.

anorectal malformation

Anorectal malformations occur in approximately 1 in 5,000 live births. This birth defect causes the anus to develop abnormally.

Anorectal malformations range from mild to severe and can affect the sphincter and other parts of the rectum and anus. Surgery is required to correct them.

anal crohn’s disease

Because Crohn’s disease can affect any part of the gastrointestinal tract from the mouth to the anus, it can also affect the anal sphincter. It is estimated that one-third of patients with Crohn’s disease have complications in the perianal region (the area of ​​the body around the anus).

People with Crohn’s disease may develop problems with their anal sphincter muscles, such as:

• abscess: Area of ​​pus that collects after infection
• crack: laceration of the anal canal
• fistula: an abnormal passageway between two parts of the body, such as the anus and the skin
• swelling: The anal sphincter may become swollen.
• ulcer: a hole or sore in the lining of an anal muscle or other structure

Anal Crohn’s disease can be managed in several different ways depending on symptoms and complications. Antibiotics are often prescribed to treat infections, and sometimes surgery may be required.

Hemorrhoids (hemorrhoids)

Hemorrhoids are swollen veins around the anus. Almost anyone can develop hemorrhoids, and they are especially problematic if you are pregnant, have inflammatory bowel disease, are over 50, or experience chronic constipation or diarrhea.

There are two types of hemorrhoids: internal hemorrhoids and external hemorrhoids. Internal hemorrhoids are located above the internal anal sphincter. External hemorrhoids are located below the external anal sphincter.

In some cases, the internal anal sphincter can trap hemorrhoids. This condition is called strangulated hemorrhoids and is extremely painful.

Hemorrhoids can usually be managed at home with topical medications and regular sitz baths. Surgery is often required to correct strangulated hemorrhoids.

fecal incontinence

Some people with IBD develop incontinence, which is the involuntary expulsion of stool from the rectum. This can occur due to recurrence of the disease or damage to the anal sphincter muscles.

A damaged anal sphincter may need to be surgically fixed. In some cases, the surgeon may be able to fix the problem simply by tightening the sphincter. In other cases, the sphincter muscle may be removed in a surgery called an anal sphincterotomy.

How long this repair lasts depends on how successful the surgery is and whether there are any complications. One study found that anal sphincter repair to prevent fecal incontinence still helped patients at least three years after surgery.

summary

The anal sphincter is a pair of muscles at the end of the rectum that control the release of stool. Damage to these muscles can make it difficult to control your bowel movements.

A variety of conditions can affect the anal sphincter, including anal fissures, anal Crohn’s disease, hemorrhoids, and fecal incontinence. These conditions range from mild to severe. Some can be corrected with home care, while others require surgery.

A word from Berrywell

The internal and external anal sphincters are muscles that work together to maintain bowel control. The anal sphincter can be affected by a variety of conditions and injuries.

Complications involving the anal sphincter are more common in people with IBD than in people without Crohn’s disease or ulcerative colitis. However, there are often treatments that can help.

Although patients may be reluctant to discuss incontinence with their doctors, it is an important sign of illness and can often be managed with treatment. If incontinence is never discussed, it certainly won’t be treated.

Perianal Crohn’s disease can be difficult to treat, and seeing (or at least seeing) a doctor who specializes in IBD can help you manage it.