On a plain abdominal radiograph of a patient with suspected bowel obstruction, which feature reliably identifies the dilated loops as small intestine rather than colon?

• A Presence of multiple gas fluid levels more than 2 cm wide
• B Haustral folds that cross only part of the luminal width
• C Peripheral arrangement of the loops with faecal loading
• D Valvulae conniventes that traverse the full width of the lumen ✓

Explanation

The valvulae conniventes of the small intestine are closely spaced mucosal folds that extend across the entire diameter of the lumen, giving the characteristic stack of coins appearance. Colonic haustra are widely spaced and indent only part of the lumen, never crossing it completely. Peripheral loops and faeces indicate colon, and fluid level measurements suggest grade of obstruction but cannot by themselves distinguish small from large bowel.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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