Imaging Protocol for Suspected Large Bowel Obstruction

Diagnostic Algorithm

The World Journal of Emergency Surgery recommends CT abdomen and pelvis with IV contrast as the primary imaging study for suspected large bowel obstruction, with superior sensitivity (93-96%) and specificity (93-100%) in confirming obstruction, identifying the cause, and determining the site 1, 2
CT provides optimal information regarding complications of cancer-related large bowel obstruction 1
Water-soluble contrast enema is a valid alternative when CT is not available, with high sensitivity (96%) and specificity (98%) for identifying the site and nature of obstruction 1, 2
Abdominal ultrasound can be used as a screening test with moderate sensitivity (88%) but is less accurate than CT 1, 2
Plain abdominal X-rays have limited sensitivity (74-84%) and specificity (50-72%) and should only be used when other modalities are unavailable 1, 2

CT scan has the highest sensitivity (93-96%) and specificity (93-100%) for confirming large bowel obstruction 1, 2
CT scan is superior for determining the cause (66-87% accuracy) and site (90-94% accuracy) of obstruction 1, 2
Water-soluble contrast enema has high sensitivity (96%) and specificity (98%) for confirming obstruction 1, 2
Abdominal ultrasound has moderate sensitivity (88%) and specificity (76%) for confirming obstruction 1, 2
Plain abdominal X-ray has limited sensitivity (74-84%) and specificity (50-72%) for confirming obstruction 1, 2

If perforation is suspected based on clinical findings or initial imaging, CT scan is recommended for stable patients to define the cause and site of perforation 1, 2
In cases of clear signs of diffuse peritonitis, CT should not delay appropriate surgical treatment 1, 2
Early involvement of a surgeon is required in cases of suspected perforation 1, 2
Plain abdominal X-rays may be inconclusive in 20-30% of cases 3