An anal fissure is a small tear in the thin, moist tissue (mucosa) that lines the anus. An anal fissure may occur when you pass hard or large stools during a bowel movement. Anal fissures typically cause pain and bleeding with bowel movements. You also may experience spasms in the ring of muscle at the end of your anus (anal sphincter).

Anal fissures are very common in young infants but can affect people of any age. An anal fissure usually heals on its own within four to six weeks. If it doesn’t, medical treatment or surgery usually can relieve discomfort.

Signs and symptoms of an anal fissure include:

• Pain, sometimes severe, during bowel movements
• Pain after bowel movements that can last up to several hours
• Bright red blood on the stool or toilet paper after a bowel movement
• Itching or irritation around the anus
• A visible crack in the skin around the anus
• A small lump or skin tag on the skin near the anal fissure

Common causes of anal fissure include:

• Passing large or hard stools
• Constipation and straining during bowel movements
• Chronic diarrhea
• Inflammation of the anorectal area, caused by Crohn’s disease or another inflammatory bowel disease
• Childbirth

• Anal cancer
• HIV
• Tuberculosis
• Syphilis
• Herpes

Factors that may increase your risk of developing an anal fissure include:

• Many infants experience an anal fissure during their first year of life; experts aren’t sure why.
• Older adults may develop an anal fissure partly due to slowed circulation, resulting in decreased blood flow to the rectal area.
• Straining during bowel movements and passing hard stools increase the risk of tearing.
• Anal fissures are more common in women after they give birth.
• Crohn’s disease. This inflammatory bowel disease causes chronic inflammation of the intestinal tract, which may make the lining of the anal canal more vulnerable to tearing.

Complications of anal fissure can include:

• Failure to heal. An anal fissure that fails to heal within six weeks is considered chronic and may need further treatment.
• Once you’ve experienced an anal fissure, you are prone to having another one.
• A tear that extends to surrounding muscles. An anal fissure may extend into the ring of muscle that holds your anus closed (internal anal sphincter), making it more difficult for your anal fissure to heal. An unhealed fissure can trigger a cycle of discomfort that may require medications or surgery to reduce the pain and to repair or remove the fissure

Your doctor will likely ask about your medical history and perform a physical exam, including inspection of the anal region. Often the tear is visible. Usually this exam is all that’s needed to diagnose an anal fissure.

Your doctor will probably refrain from performing a digital rectal exam, which involves inserting a gloved finger into your anal canal, because it is likely to be too painful. If anal fissure is suspected but can’t be identified, your doctor may use a short, lighted tube (anoscope) to inspect your anal canal.

The fissure’s location offers clues about its cause. A fissure that occurs on the side of the anal opening, rather than the back or front, is more likely to be a sign of another disorder, such as Crohn’s disease. If an underlying condition is suspected, your doctor may recommend further testing:

Flexible sigmoidoscopy. A thin, flexible tube with a tiny video camera is inserted into the bottom portion of your colon. This test may be done if you’re younger than 50 and have no risk factors for intestinal diseases or colon cancer.

Colonoscopy. A flexible tube is inserted into your rectum to inspect the entire colon. This test may be done if you are older than age 50 or have risk factors for colon cancer, signs of other conditions, or other symptoms such as abdominal pain or diarrhea.

Anal fissures often heal within a few weeks if you take steps to keep your stool soft, such as increasing your intake of fiber and fluids. Soaking in warm water for 10 to 20 minutes several times a day, especially after bowel movements, can help relax the sphincter and promote healing.

If your symptoms persist, you’ll likely need further treatment.

Your doctor may recommend:

Externally applied nitroglycerin, to help increase blood flow to the fissure and promote healing, and to help relax the anal sphincter. Nitroglycerin is generally considered the medical treatment of choice when other conservative measures fail. Side effects may include headache.

Botulin toxin type A (Botox) injection, to paralyze the anal sphincter muscle and relax spasms.

Blood pressure medications, which can help relax the anal sphincter. These medications may be taken by mouth or applied externally and may be used when nitroglycerin in not effective or causes significant side effects.

If you have a chronic anal fissure that is resistant to other treatments, or if your symptoms are severe, your doctor may recommend surgery. Surgery usually involves cutting a small portion of the anal sphincter muscle to reduce spasm and pain and promote healing. Surgery has a small risk of causing incontinence.

Several lifestyle changes may help relieve discomfort and promote healing of an anal fissure, as well as prevent recurrences:

• Add fiber to your diet. Eating about 25 to 30 grams of fiber a day can help keep stools soft and improve fissure healing. Fiber-rich foods include fruits, vegetables, nuts and whole grains. You also can take a fiber supplement. Adding fiber may cause gas and bloating, so increase your intake gradually.
• Drink adequate fluids. Fluids help prevent constipation.
• Exercise regularly. Engage in 30 minutes or more of moderate physical activity, such as walking, most days of the week. Exercise promotes regular bowel movements and increases blood flow to all parts of your body, which may promote healing of an anal fissure.
• Avoid straining during bowel movements. Straining creates pressure, which can open a healing tear or cause a new tear.

If your infant has an anal fissure, be sure to change diapers frequently, wash the area gently and discuss the problem with your infant’s doctor.

You may be able to prevent an anal fissure by taking measures to prevent constipation. Eat high-fiber foods, drink fluids and exercise regularly to keep from having to strain during bowel movements.