What radiographic signs on abdominal X-ray indicate small bowel obstruction?

• A. Gas in portal venous system.
• B. Calcifications in colon.
• C. Dilated loops of small bowel with air-fluid levels, paucity of gas in the colon, multiple air-fluid levels on erect views.
• D. Sigmoid volvulus on upright film.

Answer: (C)

Small-bowel obstruction on abdominal X-ray is suggested by dilated loops of small intestine with air-fluid levels and a paucity of gas in the colon. When the bowel is obstructed, fluid and gas accumulate proximal to the blockage; on an upright view, this produces multiple air-fluid levels as fluid settles and gas rises. The colon distal to the obstruction receives little gas, so it appears relatively gas-poor. This combination—dilated small-bowel loops with air-fluid levels and little colonic gas on an upright view—is the classic pattern for SBO. Conversely, gas in the portal venous system points to bowel ischemia or necrotizing infection, calcifications in the colon suggest other processes, and a sigmoid volvulus shows a large colonic loop with a characteristic coffee-bean sign, not primarily small-bowel obstruction.