A 62-year-old male presents with acute abdominal pain, abdominal distension, and vomiting. CT abdomen shows dilated small bowel loops with transition point at the ileocecal junction. Regarding the imaging findings in mechanical small bowel obstruction, all of the following are true EXCEPT:

Explanation

## Analysis of Small Bowel Obstruction Imaging Signs ### Key Imaging Findings in SBO **Key Point:** The hallmark of mechanical SBO on imaging is identification of the transition zone — the abrupt change from dilated proximal bowel to collapsed distal bowel. ### Evaluation of Each Statement | Finding | True/False | Explanation | |---------|-----------|-------------| | Transition zone | TRUE | Represents the point of mechanical obstruction; crucial for localization | | String sign | TRUE | Seen in adhesions; appears as a thin linear density of narrowed bowel | | Haustra preservation | FALSE | Haustra are features of **large bowel**, not small bowel. Small bowel has **plicae circulares** (valvulae conniventes), which are often obliterated in obstruction | | Bird's beak sign | TRUE | Classic finding in volvulus; shows the twisted mesentery at the point of torsion | ### Why Haustra Are the Wrong Answer **High-Yield:** Small bowel and large bowel have distinct mucosal patterns: - **Small bowel:** Plicae circulares (valvulae conniventes) — extend across the entire width of the lumen - **Large bowel:** Haustra — incomplete, do not cross the full width In small bowel obstruction, these plicae are often **lost or stretched** due to luminal distension, not preserved. Haustra are not a feature of small bowel at all. ### Clinical Pearl **Tip:** When evaluating SBO imaging, look for: 1. Dilated small bowel loops (>3 cm diameter) 2. Transition zone identifying obstruction site 3. Collapsed distal bowel 4. Specific signs (string, bird's beak, whirlpool) indicating etiology Haustra preservation would actually suggest large bowel obstruction, not small bowel obstruction.