Large bowel obstruction

Acute colonic distension can occur due to the following causes:

  • Mechanical obstruction

  • Toxic megacolon (eg, as a complication of inflammatory bowel disease or Clostridium difficile infection)

  • Acute colonic pseudo-obstruction (Ogilvie's syndrome)

This pathway deals with large bowel obstruction due to mechanical causes. Toxic megacolon and acute colonic pseudo-obstruction (Ogilvie’s syndrome) are discussed in the following links.

Step 1: Pathway Entry


  • Abdominal pain (normally colicky), bloating, change in bowel habit, tenesmus, rectal bleeding, recent weight loss, nausea and vomiting


  • Abdominal distension, tympanic abdomen, abdominal tenderness, abdominal rigidity, palpable rectal mass or empty rectum

Risk factors:

  • Malignancy (colorectal cancers and other neoplasms e.g. pancreatic ca, ovarian ca, lymphoma)

  • Prior abdominal surgery, especially prior colorectal resection and stricture formation

  • Strictures (i.e. diverticular, inflammatory, ischaemic, radiation-induced, or anastomotic)
  • Volvulus - common in institutionalised elderly patients (5%)

  • Rare causes include hernia, foreign body, benign neoplasm, gynaecological neoplasm, pelvic abscess, or endometriosis

Step 2: Is the Patient Stable?

  • Initiate resuscitation measures if required.

  • Consideration of other life-threatening diagnoses with similar symptoms (Perforated viscus, Pancreatitis, AAA)

Step 3: Detailed Initial Assessment

In the stable patient a thorough assessment is the next step including a detailed history, a detailed examination, blood tests including FBC, EUC, LFTs, lipase, BSL, an ECG and a CXR. Beta-HCG in women of childbearing age, VBG for lactate.

If an alternative diagnosis is made at this time then the steps further down the pathway can be curtailed.

Step 4: Imaging

Plain films: may demonstrate volvulus or pneumoperitoneum.

CT abdomen: more sensitive and specific for colorectal obstruction than plain films (>90% each). Will also distinguish between true obstruction and pseudo-obstruction, as well as determine the cause of obstruction and complications.

Step 5: Management

Supportive care

  • NBM

  • IV fluids

  • Monitor urine output

  • Analgesia

  • NG tube usually unnecessary, may be used if there is severe distension and vomiting

If there is evidence of perforation or impending perforation, emergency surgery is indicated. In the absence of perforation, definitive treatment depends on cause. Treatment in most cases of mechanical large bowel obstruction is surgery, with the exception of:

  • Sigmoid volvulus, where first line treatment is flexible or rigid sigmoidoscopy and insertion of a rectal tube.

  • Benign strictures, which should be treated based on the severity of symptoms, the underlying disease process, and the patient's general condition.

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