Large bowel obstruction

Last reviewed: 3 May 2023
Last updated: 31 Jan 2023



History and exam

Key diagnostic factors

  • intermittent abdominal pain
  • abdominal distention
  • nausea
  • vomiting
  • change in bowel habit
  • presence of risk factors
  • hard faeces
  • soft stools
  • empty rectum
  • recent weight loss
  • rectal bleeding
  • palpable rectal mass
  • palpable abdominal mass
  • tympanic abdomen
  • fever
  • abdominal tenderness
  • abdominal rigidity
Full details

Other diagnostic factors

  • tenesmus
Full details

Risk factors

  • colorectal adenomas or polyps
  • current or previous malignancy
  • inflammatory bowel disease
  • diverticular disease
  • current or previous hernia
  • gynaecological conditions
  • diabetes
  • previous abdominal surgery
  • previous radiotherapy
  • family history of bowel cancer
  • age
  • male sex
  • obesity
  • megacolon
  • laxative abuse
  • diet
  • alcohol consumption
  • smoking
Full details

Diagnostic investigations

1st investigations to order

  • computed tomography
  • full blood count
  • electrolytes
  • C-reactive protein
  • urea/creatinine ratio
  • glucose
  • clotting, group and save, or cross-match
  • arterial blood gas (including lactate)
Full details

Investigations to consider

  • beta-human chorionic gonadotrophin
  • urinalysis
  • electrocardiogram
  • water-soluble contrast study
  • lower gastrointestinal endoscopy or flexible sigmoidoscopy
Full details

Treatment algorithm


suspected or impending perforation




benign strictures

diverticular disease

currently receiving palliative care


Expert advisers

John Abercrombie, FRCS

General and Colorectal Surgeon

Queen’s Medical Centre




JA is a member of the Council of the Royal College of Surgeons of England and Clinical Lead for General Surgery, Getting It Right First Time. JA provides expert advice regarding suitability of surgical treatments for Spire Healthcare.


BMJ Best Practice would like to gratefully acknowledge the previous team of expert contributors, whose work is retained in parts of the content:

George Malietzis, MBBS, MSc, MRCS

Colorectal Registrar

Department of Coloproctology

St Mark's Hospital



John T. Jenkins, MD

Consultant Colorectal Surgeon

Department of Coloproctology

St. Mark's Hospital



Peer reviewers

Ceri Beaton, BMedsci, BMBS, MSc, FRCS

Consultant Colorectal and General Surgeon

North Devon Healthcare NHS Trust

Devon UK


CB declares that she has no competing interests.


Emma Quigley

Section Editor, BMJ Best Practice


EQ declares that she has no competing interests.

Tannaz Aliabadi-Oglesby

Lead Section Editor, BMJ Best Practice


TAO declares that she has no competing interests.

Sue Mayor

Lead Section Editor, BMJ Best Practice


SM works as a freelance medical journalist and editor, video editorial director and presenter, and communications trainer. In this capacity, she has been paid, and continues to be paid, by a wide range of organisations for providing these skills on a professional basis. These include: NHS organisations, including NICE, NHS Choices, NHS Kidney Care, and others; publishers and medical education companies, including the BMJ Group, the Lancet group, Medscape, and others; professional organisations, including the British Thoracic Oncology Group, the European Society for Medical Oncology, NCEPOD, and others; charities and patients’ organisations, including the Roy Castle Lung Cancer Foundation and others; pharmaceutical companies, including Bayer, Boehringer Ingelheim, Novartis, and others; and communications agencies, including Publicis, Red Healthcare, and others. She has no stock options or shares in any pharmaceutical or healthcare companies; however, she invests in a personal pension, which may invest in these types of companies. She is managing director of Susan Mayor Limited, the company name under which she provides medical writing and communications services.

Annabel Sidwell

Comorbidities Editor, BMJ Best Practice


AS declares that she has no competing interests.

Adam Mitchell

Drug Editor, BMJ Best Practice


AM declares that he has no competing interests.

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