Large Bowel Obstruction: Findings on Abdominal X-ray
Authors: Shayan Hemmati Reviewers: Reshma Sirajee, Tara Shannon, *Stephanie Nguyen, *MD at the time of publication
Radiopaedia, rID:18015
Common causes of obstruction are colorectal carcinoma (60-80%) and cecal or sigmoid volvulus (11-15%)
Obstruction from mechanical causes such as physical blockade of bowel lumen or twisting of the large bowel
Bowel Obstruction
*See Mechanical Bowel Obstruction and Ileus: Pathogenesis and clinical findings
Large bowel contents cannot pass the obstructionàgas buildup in colon from swallowed air, bacterial fermentation, CO2 from acid + bicarbonate reaction
Colon intraluminal pressure overcomes venous and lymphatic pressure
Impaired venous outflowàbowel wall edema/thickening
↑ Vascular resistance eventually impedes arterial inflowàbowel wall ischemia
Ischemia can progress to bowel infarction and necrosis
Large bowel loops are anatomically peripheral to the small bowel
Evacuation of gas and water reabsorption distal to obstruction
If ileocecal (IC) valve incompetent or sufficient pressure buildup in large bowel can overcome IC valve
↑ intraluminal pressure
Gas dissects into
bowel wall from mucosal disruption
Pneumatosis coli (air within bowel wall)
Bowel wall perforation (especially when cecum diameter > 10-12cm)
Dilated large bowel loops located peripherally (highlighted yellow)
Collapsed distal colon (few or no air-fluid levels in the large bowel as water is reabsorbed)
Small bowel dilatation (> 3 cm)
Colonic dilatation (> 6 cm)
Cecum dilatation (> 9 cm)
Haustra (anatomical folds of the large bowel) become visible as it is distended
Pneumoperitoneum (sub-diaphragmatic air on erect chest x-ray)
Release of gas into peritoneum
PA
Radiopaedia, rID:17957
PA
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published February 16, 2023 on www.thecalgaryguide.com