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Toxic colitis and toxic megacolon

Evidence last reviewed: 3 May 2026
Topic last updated: 22 May 2026

Summary

Definition

History and exam

Key diagnostic factors

  • history of inflammatory bowel disease
  • history of exposure to infectious agents
  • history of recent antibiotic use
  • history of HIV/AIDS/immunosuppressed state
  • fevers/chills
  • tachycardia
  • mental status changes
  • hypotension
  • abdominal distention
Full details

Other diagnostic factors

  • diarrhea
  • abdominal pain
  • abdominal tenderness
Full details

Risk factors

  • ulcerative colitis (UC)
  • Crohn colitis
  • pseudomembranous colitis
  • infectious colitis
  • HIV/AIDS/immunosuppression
  • discontinuation of drug treatments for inflammatory bowel disease
  • use of antimotility drugs
  • use of chemotherapy or immunosuppressants
  • electrolyte abnormalities
Full details

Diagnostic tests

1st tests to order

  • CBC
  • serum urea and electrolytes
  • serum albumin levels
  • serum lactate
  • stool studies
  • CT abdomen/pelvis
  • abdominal x-ray
  • chest x-ray
Full details

Tests to consider

  • CRP
  • erythrocyte sedimentation rate (ESR)
  • blood cultures
  • arterial blood gas
  • flexible sigmoidoscopy
  • rectal biopsy
  • surgical specimen
Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

Jan Rakinic, MD

Chief

Colorectal Surgery

Department of Surgery

Southern Illinois University School of Medicine

Springfield, IL

Disclosures

JR declares that she has no competing interests.

V. Prasad Poola, MBBS, FACS, FASCRS

Associate Professor of Surgery

Department of Surgery

Southern Illinois University School of Medicine

Springfield, IL

Disclosures

VPP declares that he has no competing interests.

Acknowledgements

Dr Jan Rakinic and Dr V. Prasad Poola would like to gratefully acknowledge Dr Scott A. Strong, Dr Mukta V. Krane, and Dr Alessandro Fichera, previous contributors to this topic.

Disclosures

SAS, MVK, and AF declare that they have no competing interests.

Peer reviewers

Marianne V. Cusick, MD, MSPH

Divisional Director

Colon & Rectal Surgery

UTHealth Houston

Houston, TX

Disclosures

MVC declares that she has no competing interests.

Sharon Stein, MD

Assistant Professor of Surgery

Division of Colon and Rectal Surgery

University Hospital Case Medical Center

Cleveland, OH

Disclosures

SS received a fee for educational courses on laparoscopic surgery, paid for in part by Covidien, Olympus, and Applied Medical.

David J. Hackam, MD, PhD

Associate Professor of Pediatric Surgery

University of Pittsburgh School of Medicine

Pittsburgh, PA

Disclosures

DJH declares that he has no competing interests.

James Wheeler, MB, BCh, MD, FRCS

Consultant

Colorectal Surgeon

Addenbrookes Hospital

Cambridge

UK

Disclosures

JW 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

Rubin DT, Ananthakrishnan AN, Siegel CA, et al. ACG clinical guideline update: ulcerative colitis in adults. Am J Gastroenterol. 2025 Jun 3;120(6):1187-224.Full text  Abstract

Poylin V, Hawkins AT, Bhama AR, et al. The American Society of Colon and Rectal Surgeons clinical practice guidelines for the management of Clostridioides difficile infection. Dis Colon Rectum. 2021 Jun 1;64(6):650-68.Full text

Kelly CR, Fischer M, Allegretti JR, et al. ACG clinical guidelines: prevention, diagnosis, and treatment of Clostridioides difficile infections. Am J Gastroenterol. 2021 Jun 1;116(6):1124-47.Full text  Abstract

McDonald LC, Gerding DN, Johnson S, et al. Clinical practice guidelines for Clostridium difficile infection in adults and children: 2017 update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA). Clin Infect Dis. 2018 Mar 19;66(7):987-94.Full text  Abstract

Holubar SD, Lightner AL, Poylin V, et al. The American Society of Colon and Rectal Surgeons clinical practice guidelines for the surgical management of ulcerative colitis. Dis Colon Rectum. 2021 Jul 1;64(7):783-804.Full text

Reference articles

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

    • ACG clinical guideline update: ulcerative colitis in adults
    • Prevention, diagnosis, and treatment of Clostridioides difficile infections
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