A 58-year-old woman with a history of previous abdominal surgery presents with acute abdominal pain, distension, and bilious vomiting. CT abdomen with IV contrast is performed. Regarding the imaging findings and signs of strangulation in small bowel obstruction, all of the following are reliable indicators of bowel ischemia EXCEPT:

Explanation

## CT Imaging Signs of Strangulation in Small Bowel Obstruction ### Reliable Indicators of Bowel Ischemia **Key Point:** Strangulation (compromise of blood supply) is a surgical emergency and must be detected early on imaging. CT with IV contrast is the gold standard for identifying ischemic changes in small bowel obstruction (SBO). | CT Finding | Significance | Reliability for Ischemia | |---|---|---| | Mesenteric edema & fat stranding | Non-specific; seen in uncomplicated SBO due to venous congestion | **Low–Moderate (non-specific)** | | Loss of bowel wall enhancement | Transmural necrosis and loss of perfusion | High | | Closed-loop configuration + thickened wall | Vascular compromise with edema/ischemic injury | High | | Free fluid (small amount, exudative) | Exudative fluid from ischemic bowel | Moderately high | ### Analysis of Each Option **Option A — Mesenteric edema and fat stranding (EXCEPT answer):** This is the LEAST reliable indicator of bowel ischemia among the options. Mesenteric edema and fat stranding are commonly seen in **uncomplicated** small bowel obstruction due to venous congestion, lymphatic obstruction, and local inflammation—even without ischemia. Per Federle's *Diagnostic Imaging: Abdomen* and Maglinte et al., these findings are non-specific and cannot reliably distinguish simple obstruction from strangulation. They are therefore NOT a reliable indicator of ischemia. **Option B — Absence of normal bowel wall enhancement:** TRUE indicator of ischemia. Loss of normal enhancement after IV contrast indicates transmural necrosis and severely compromised perfusion—a hallmark of strangulation. This is one of the most specific and reliable CT signs (Paulson & Thompson, *Radiology*, 2015). **Option C — Presence of free fluid without ascites:** TRUE indicator of ischemia. A small amount of localized free fluid (exudative fluid from ischemic bowel serosa) is a recognized and moderately reliable sign of strangulation in SBO. It is distinct from large-volume ascites, which is non-specific. Radiological literature (Balthazar et al.) supports free fluid as a sign of strangulation. **Option D — Closed-loop configuration with thickened bowel wall:** TRUE indicator of ischemia. A closed-loop obstruction (internal hernia, adhesive band, volvulus) with a swollen, thickened bowel wall reliably indicates vascular compromise and ischemic injury. This is a high-specificity finding for strangulation. **High-Yield:** The most specific CT signs of strangulation are: (1) loss of bowel wall enhancement, (2) closed-loop configuration with thickened wall, and (3) localized free fluid. Mesenteric fat stranding alone is non-specific and is seen in uncomplicated SBO as well. **Clinical Pearl:** Mesenteric fat stranding should be interpreted in context—its presence alone should not be used to diagnose strangulation. The combination of loss of enhancement + closed-loop + free fluid is far more predictive of ischemia requiring urgent surgery.