A 68-year-old man presents with acute onset colicky abdominal pain and abdominal distension. Plain abdominal radiograph shows multiple air-fluid levels with a 'step-ladder' appearance and dilated small bowel loops. Which of the following radiographic signs is NOT typically associated with small bowel obstruction?

Explanation

## Radiographic Signs of Small Bowel Obstruction **Key Point:** Small bowel obstruction (SBO) has characteristic plain film signs that distinguish it from colonic obstruction and other acute abdominal pathology. ### Correct Signs of Small Bowel Obstruction | Sign | Description | Pathophysiology | |------|-------------|------------------| | **Valvulae conniventes** | Plicae circulares crossing entire bowel width | Normal mucosal folds of small bowel | | **Air-fluid levels** | Step-ladder or staircase pattern | Proximal bowel dilation with proximal obstruction | | **String of pearls** | Mesenteric plication appearance | Clustered air-filled loops in closed-loop obstruction | | **Absence of rectal gas** | No gas visible in rectum | Distal obstruction preventing gas passage | ### Why Haustra Are Wrong **High-Yield:** Haustra are the characteristic haustrual markings of the **colon**, not the small bowel. Haustra: - Do NOT cross the entire width of the colonic lumen (they are incomplete) - Are the normal anatomical feature of the colon - Indicate colonic pathology when dilated, not small bowel obstruction **Clinical Pearl:** The distinction between small bowel and colonic obstruction on plain film is critical because: - SBO is usually managed conservatively initially (nasogastric decompression) - Colonic obstruction often requires urgent intervention (volvulus, malignancy) ### Mnemonic for SBO Signs **VACS** — Valvulae conniventes, Air-fluid levels, Coiled spring (string of pearls), Step-ladder pattern **Warning:** Do not confuse haustra (colon) with valvulae conniventes (small bowel). Haustra are incomplete and do not span the entire bowel width; valvulae conniventes are complete and do.