Merck Manual

Please confirm that you are a health care professional

honeypot link

Anal Fissure

(Fissure in Ano; Anal Ulcer)


Parswa Ansari

, MD, Hofstra Northwell-Lenox Hill Hospital, New York

Last full review/revision Feb 2021| Content last modified Feb 2021
Click here for Patient Education
Topic Resources

An anal fissure is an acute longitudinal tear or a chronic ovoid ulcer in the squamous epithelium of the anal canal. It causes severe pain, sometimes with bleeding, particularly with defecation. Diagnosis is by inspection. Treatment is local hygiene, stool softeners, topical measures, and sometimes botulinum toxin injection and/or a surgical procedure.

Anal fissures are believed to result from laceration by a hard or large stool or from frequent loose bowel movements. Trauma (eg, anal intercourse) is a rare cause. The fissure may cause internal sphincter spasm, decreasing blood supply and perpetuating the fissure.

Symptoms and Signs of Anal Fissure

Anal fissures usually lie in the posterior midline but may occur in the anterior midline. Those off the midline may have specific etiologies, particularly Crohn disease Crohn Disease Crohn disease is a chronic transmural inflammatory bowel disease that usually affects the distal ileum and colon but may occur in any part of the gastrointestinal tract. Symptoms include diarrhea... read more Crohn Disease . An external skin tag (the sentinel pile) may be present at the lower end of the fissure, and an enlarged (hypertrophic) papilla may be present at the upper end.

Fissures cause pain and bleeding. The pain typically occurs with or shortly after defecation, lasts for several hours, and subsides until the next bowel movement. Examination must be gentle but with adequate spreading of the buttocks to allow visualization.

Infants may develop acute fissures, but chronic fissures are rare.

Diagnosis of Anal Fissure

  • Clinical evaluation

Diagnosis of anal fissure is made by inspection. Unless findings suggest a specific cause or the appearance and/or location is unusual, further studies are not required.

Treatment of Anal Fissure

  • Stool softeners

  • Protective ointments, sitz baths

  • Nitroglycerin ointment, topical calcium channel blocker, or botulinum toxin type A injection

(See also the American Society of Colon and Rectal Surgeons’ clinical practice guideline for the management of anal fissures.)

Fissures often respond to conservative measures that minimize trauma during defecation (eg, stool softeners, psyllium, fiber). Healing is aided by use of protective zinc oxide ointments or bland suppositories (eg, glycerin) that lubricate the lower rectum and soften stool. Topical anesthetics (eg, benzocaine, lidocaine) and warm (not hot) sitz baths for 10 or 15 minutes after each bowel movement and as needed give temporary relief.

Topical nitroglycerin 0.2% ointment, nifedipine cream 0.2%, 2% diltiazem gel, and injections of botulinum toxin type A into the internal sphincter relax the anal sphincter and decrease maximum anal resting pressure, allowing healing. When conservative measures fail, surgery (internal anal sphincterotomy) is needed to interfere with the cycle of internal anal sphincter spasm.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

Drugs Mentioned In This Article

Drug Name Select Trade
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
quiz link

Test your knowledge

Take a Quiz!