Large bowel obstruction


Average inner diameters and ranges of different sections of the large intestine.[1]
  • Much less common than SBO, but more ominous (frequently associated with malignancy)
    • LBO more common in elderly, and generally has more insidious onset than SBO
  • Most commonly occurs in the left (descending) colon
    • Obstruction originating from the left colon is likely to manifest with symptoms earlier than obstruction originating from the right colon, because the lumen from the descending colon and the sigmoid is smaller.


Clinical Features

  • Abdominal pain
  • Abdominal distension
    • Distention is greater if the ileocecal valve is competent (it creates a closed loop obstruction). If the ileocecal valve is not competent, you are more likely to see some dilation of the small bowel as well [2]
  • Obstipation
  • Vomiting
  • Palpable abdominal mass (could be distended bowel or could be tumor causing obstruction)
  • Fever and tachycardia should prompt investigation for gangrene and perforation

Differential Diagnosis

Diffuse Abdominal pain


Upright abdominal X-ray of a person with a large bowel obstruction showing multiple air fluid levels and dilated loops of bowel.
Large bowel obstruction (Cecal volvulus; black arrows).
  • Labs
    • None are diagnostic
    • Check electrolytes to assess for dehydration
    • Leukocytosis could indicate gangrene or perforation
    • Anemia could indicate malignancy as source of obstruction
    • ABG may help assess if the patient has respiratory compromise from diaphragmatic compression [3]
  • Imaging [4]
    • Use the 3/6/9 rule for bowel imaging
      • Upper limit of 3cm for small bowel, 6cm for colon, and 9cm for cecum
    • XR
      • Sensitivity of 69% to 80% for detecting bowel obstruction, but insensitive for diagnosing cause or location
      • Upright films can detect pneumoperitoneum, hollow viscus perforation
      • Distended colon (small bowel may appear distended as well if the ileocecal valve is competent)
      • Cecal diameter of ≥12cm is associated with higher risk of perforation, ≥9cm is associated with obstruction
      • Large bowel diameter ≥5-6cm is associated with obstruction
    • CT
      • Can usually identify the cause of obstruction, except in cases of pseudo-obstruction
      • Sensitivity for diagnosing large bowel obstruction as high as 90% (not as high as for small bowel obstruction)
      • Can also diagnose intestinal ischemia
    • Colonoscopy
      • Can be used to rule-out pseudo-obstruction in patients who are not candidates for urgent surgical intervention


  • IV hydration
  • NPO
  • Pain management
  • Place NGT if patient has significant vomiting or evidence of small bowel distension
  • Antibiotics if gangrene or perforation is suspected (cover gram-negative and anaerobics)
  • Consult GI, surgery, IR as appropriate

Treatment for specific etiologies


  • Admit

See Also


  1. Nguyen H, Loustaunau C, Facista A, Ramsey L, Hassounah N, Taylor H, et al. (July 2010). "Deficient Pms2, ERCC1, Ku86, CcOI in field defects during progression to colon cancer". Journal of Visualized Experiments (41). doi:10.3791/1931. PMC 3149991. PMID 20689513.
  2. Jaffe T, Thompson WM. Large-Bowel Obstruction in the Adult: Classic Radiographic and CT Findings, Etiology, and Mimics. Radiology. 2015; 275(3):651-663
  3. Lopez-Kostner F, Hool GR, et al. Management and Causes of Acute Large-Bowel Obstruction.. Surgical Clinics of North America. 1997; 77(6); 1265-1290
  4. Murphy K, Twomey M, McLaughlin P, et al. Imaging of Ischemia, Obstruction and Infection in the Abdomen. Radiology Clinics of North America. 2105; 53: 847-869