A 68-year-old man presents with acute onset abdominal pain, abdominal distension, and vomiting. Plain abdominal radiograph shows multiple dilated small bowel loops with air-fluid levels and a transition point in the left lower quadrant. Which of the following radiographic signs is NOT typically associated with small bowel obstruction?

Explanation

## Distinguishing Small Bowel from Colon on Plain Radiography **Key Point:** The hallmark radiographic signs of small bowel obstruction rely on the characteristic mucosal fold patterns and distribution of gas, which differ fundamentally from the colon. ### Small Bowel Obstruction — Classic Signs **High-Yield:** The three cardinal radiographic features are: 1. **Valvulae conniventes (plicae circulares)** — thin mucosal folds that cross the *entire width* of the small bowel lumen. These are the most specific sign of small bowel involvement. 2. **Stepladder or accordion pattern** — dilated small bowel loops arranged in a characteristic staircase configuration, reflecting the peristaltic attempts against the obstruction. 3. **Air-fluid levels** — horizontal levels visible on upright or decubitus films, indicating fluid accumulation proximal to the obstruction. ### Why Haustra Are Wrong **Clinical Pearl:** Haustra are the *colonic* equivalent of valvulae conniventes. They are: - Larger, more widely spaced mucosal folds - **Do NOT extend completely across the colonic lumen** — they are interrupted by the taeniae coli (longitudinal muscle bands) - A sign of **colonic** obstruction, not small bowel obstruction **Warning:** Confusing haustra with valvulae conniventes is a classic trap. Remember: valvulae = complete width (small bowel); haustra = interrupted (colon). ### Comparison Table | Feature | Small Bowel | Colon | | --- | --- | --- | | Mucosal fold pattern | Valvulae conniventes (plicae circulares) | Haustra | | Fold completeness | Cross entire lumen | Interrupted by taeniae coli | | Diameter (normal) | < 3 cm | < 6 cm | | Location of dilation in obstruction | Proximal to transition point | Proximal to transition point | | Pattern | Stepladder/accordion | Haustra-containing loops | **Mnemonic:** **HAUSTRAL** = **H**austra = **A**lways **U**ninterrupted **S**tructures **T**hat **R**un **A**cross **L**ongitudinally (actually: interrupted by taeniae — but the point is they don't cross completely). ### Clinical Correlation In this case, the transition point in the left lower quadrant with dilated proximal small bowel loops suggests a small bowel obstruction (likely adhesion, hernia, or Crohn's disease). The presence of valvulae conniventes and stepladder pattern confirms small bowel origin. Haustra would indicate colonic involvement and would be seen in colonic obstruction (volvulus, carcinoma, diverticulitis with perforation).