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Anorectal abscess

  • Overview
  • Theory
  • Diagnosis
  • Management
  • Follow up
  • Resources
Last reviewed: 14 Apr 2025
Last updated: 21 Dec 2022

Summary

Definition

History and exam

Key diagnostic factors

  • anal fistula
  • history of Crohn disease
  • male sex
  • perianal pain
  • perianal or rectal induration
Full details

Other diagnostic factors

  • perianal swelling
  • low-grade fever
  • tachycardia
  • change in bowel habits
  • rectal bleeding
  • inability to urinate
Full details

Risk factors

  • anal fistula
  • Crohn disease
  • male sex
  • hard stools
  • age 21 to 40 years
Full details

Diagnostic tests

1st tests to order

  • clinical examination
  • examination under anesthetic
Full details

Tests to consider

  • WBC count
  • serum glucose
  • serum electrolytes
  • anal ultrasonography
  • CT pelvis
  • MRI pelvis
  • microscopic examination and/or culture of the purulent fluid
Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

Jan Rakinic, MD, FACS, FASCRS

Professor of Surgery

Chief

Section of Colorectal Surgery

Southern Illinois University School of Medicine

Springfield

IL

Disclosures

JR is an author of a reference cited in this topic.

Acknowledgements

Dr Jan Rakinic would like to gratefully acknowledge Dr C. Neal Ellis, a previous contributor to this topic.

Disclosures

CNE declares that he has no competing interests.

Peer reviewers

Mark H. Whiteford, MD

Assistant Professor of Surgery

Colon and Rectal Surgery

Gastrointestinal and Minimally Invasive Surgery Division

The Oregon Clinic

Portland

OR

Disclosures

MHW declares that he has no competing interests.

Neil Hyman, MD

Chief

Division of General Surgery

Professor of Surgery

Fletcher Allen Healthcare

Burlington

VT

Disclosures

NH declares that he has no competing interests.

Steven Brown, MBChB, FRCS, MD, BMedSci

Consultant Surgeon

Department of Colorectal Surgery

Sheffield Teaching Hospitals

Sheffield

UK

Disclosures

SB declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Gaertner WB, Burgess PL, Davids JS, et al. The American Society of Colon and Rectal Surgeons clinical practice guidelines for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula. Dis Colon Rectum. 2022 Aug 1;65(8):964-85.Full text  Abstract

Nomikos IN. Anorectal abscesses: need for accurate anatomical localization of the disease. Clin Anat. 1997;10:239-44. Abstract

Wright WF. Infectious diseases perspective of anorectal abscess and fistula-in-ano disease. Am J Med Sci. 2016 Apr;351(4):427-34. Abstract

Malik AI, Nelson RL, Tou S. Incision and drainage of perianal abscess with or without treatment of anal fistula. Cochrane Database Syst Rev. 2010 Jul 7;(7):CD006827.Full text  Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
  • Anorectal abscess images

  • Differentials

    • Anal fissure
    • Thrombosed hemorrhoid
    • Pilonidal abscess
    More Differentials

  • Guidelines

    • The American Society of Colon and Rectal Surgeons clinical practice guidelines for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula
    • ACR appropriateness criteria: anorectal disease
    More Guidelines
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