Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android. Learn more here!

For further information, see CMDT Part 15-44: Other Anal Conditions

Key Features

  • Infection of anal glands located at the base of the anal crypts at the dentate line, leading to abscess formation

  • Causes include

    • Anal fissure

    • Crohn disease

  • Fistula in ano arises in an anal crypt and is usually preceded by an anal abscess

  • Causes of fistulas that connect to the rectum include

    • Crohn disease

    • Lymphogranuloma venereum

    • Rectal tuberculosis

    • Cancer

Clinical Findings

  • Perianal abscess: throbbing, continuous perianal pain

    • Erythema, fluctuance, and swelling in the perianal region on external examination

    • Swelling in the ischiorectal fossa on digital rectal examination

  • Fistula in ano: purulent discharge, itching, tenderness, and pain


  • Perianal abscess is treated by surgical incision under local anesthesia

  • Ischiorectal abscess is treated by surgical drainage in the operating room

  • Fistula in ano is treated by surgical excision under anesthesia

  • Fistulas caused by Crohn disease are frequently asymptomatic

  • Surgical fistulotomy for complex (high, transphincteric) anal fissures carries a high risk of incontinence

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.