Evaluation of ischemia and necrosis in adhesive small bowel obstruction based on CT signs: Subjective visual evaluation and objective measurement.

PURPOSE: To investigate the diagnostic performance of CT signs for detecting bowel ischemia and necrosis in adhesive small bowel obstruction(SBO) with subjective and objective methods. MATERIALS AND METHODS: 113 adhesive SBO patients were enrolled and divided into ischemic group (49 cases in necrotic group and 35 cases in reversible ischemic group) and non-ischemic group (29 cases) according to the operation results. Subjective visual assessment of CT signs associated with ischemia and necrosis was performed by two radiologists independently. Elevated unenhanced attenuation and enhancement value of involved bowel wall were objectively measured and compared by single factor analysis of variance. Cut-off value and diagnostic performance were evaluated by receiver operating characteristic curve (ROC). RESULTS: Closed-loop mechanism, reduced bowel wall enhancement, and mesenteric edema were associated with bowel ischemia, with sensitivity of 81.0%, 65.5%, 75.0%, and specificity of 86.2%, 96.6%, 89.7%, respectively. Increased unenhanced bowel wall attenuation was a specific sign for necrosis with 100.0% specificity and 51.0% sensitivity. The sensitivity and specificity for ischemia were 86.0% and 91.9% with cut-off enhancement value lower than 33.5 HU. The sensitivity and specificity for necrosis were 58.2% and 100.0% with cut-off elevated unenhanced attenuation higher than 16.5 HU, 86.7% and 83.3% with cut-off enhancement value lower than 21.5 HU. CONCLUSION: Reduced bowel wall enhancement and increased unenhanced bowel wall attenuation were good indicators of bowel ischemia and necrosis. The objective measurement of elevated unenhanced attenuation and enhancement value can predict bowel ischemia and necrosis more accurately.