Anorectal abscess

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 11 Aug 2025

Last updated: 21 Dec 2022

Anorectal abscess commonly presents with perianal pain with leukocytosis.

Usually treated by incision and drainage.

Adjunctive antibiotics are unnecessary for uncomplicated cases. Antibiotics are indicated for patients with associated cellulitis, immunocompromise, signs of systemic infection, diabetes, or a history of cardiac valvular disease.

Definition

An anorectal abscess is an infection of the soft tissues around the anus.[1] Severe perianal pain and swelling are the most common presenting complaints. Other symptoms include fever, chills, or urinary retention.[2] Rarely, patients may present with life-threatening sepsis from an associated necrotising soft-tissue infection.[3] The diagnosis of an anorectal abscess can usually be made by physical examination, but occasionally atypical or occult abscesses require a computed tomography scan, ultrasound, or magnetic resonance imaging.[4][5][6]

History and exam

Key diagnostic factors

anal fistula
history of Crohn's 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's disease
male sex
hard stools
age 21 to 40 years

Full details

Diagnostic investigations

1st investigations to order

clinical examination
examination under anaesthetic

Full details

Investigations 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

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

Disclosures

MHW declares that he has no competing interests.

Neil Hyman, MD

Chief

Division of General Surgery

Professor of Surgery

Fletcher Allen Healthcare

Burlington

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

Disclosures

SB declares that he has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

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.

Differentials
- Anal fissure
- Thrombosed haemorrhoid
- 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
Log in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer

Anorectal abscess

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

all patients

Contributors

Authors

Jan Rakinic, MD, FACS, FASCRS

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Mark H. Whiteford, MD

Disclosures

Neil Hyman, MD

Disclosures

Steven Brown, MBChB, FRCS, MD, BMedSci

Disclosures

Peer reviewer acknowledgements

Disclosures

References

Key articles

Reference articles

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

Differentials

Guidelines

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice