On a plain supine abdominal radiograph, which feature best distinguishes dilated small bowel from dilated large bowel?

• A Small bowel loops are always central and large bowel loops are always peripheral
• B Haustral folds traverse the entire width of the lumen
• C Valvulae conniventes (plicae circulares) traverse the entire width of the lumen ✓
• D Dilated small bowel contains faecal loading while colon contains gas only

Explanation

Valvulae conniventes are closely spaced mucosal folds that extend across the whole width of the small bowel lumen, whereas haustra are incomplete and do not cross the full diameter. Loop position is only a soft sign because a grossly dilated transverse colon can lie centrally, so option A is unreliable. Faecal loading occurs in colon, not small bowel.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.