Value of dual-energy computed tomography in the diagnosis of bowel ischemia in patients with mechanical small-bowel obstruction: a retrospective, dual-center study

Abstract

OBJECTIVES: To investigate the diagnostic value of rapid-kV-switching dual-energy CT (DECT) for identifying bowel ischemia in patients with mechanical small-bowel obstruction (SBO), compared to 120 kVp-equivalent CT. MATERIALS AND METHODS: This retrospective dual-center study included 112 patients with mechanical SBO. Clinical and surgical outcomes with histological findings were recorded as the reference standard. Three readers independently reviewed true unenhanced (TUE) and portal-venous 77-keV virtual monoenergetic images (VMI) (dataset#1), virtual unenhanced (VUE), iodine, and 50-keV VMI (dataset#2). Ischemia was defined as the presence of at least two CT features among reduced bowel-wall enhancement, diffuse mesenteric haziness, and a closed-loop mechanism. Unenhanced bowel-wall attenuation was also analysed. Bowel-wall attenuation and iodine concentration were measured in involved loops and proximal dilated loops. Sensitivity and specificity were calculated for each CT feature. Association between iodine concentration and bowel ischemia was analysed using ROC curves. RESULTS: Forty-one (37%) patients underwent surgery. Twenty-four (21%) patients had findings of bowel ischemia, including 11 (10%) patients with irreversible ischemia (necrosis). Diagnostic performance for ischemia and necrosis was similar between both datasets for all readers (p > 0.49 for ischemia and p = 1 for necrosis). Increased bowel-wall attenuation on VUE or TUE images had a non-significantly different diagnostic value for all readers (p > 0.21 for ischemia and p > 0.78 for necrosis). Bowel-wall iodine concentration identified bowel necrosis with 82% sensitivity and 83% specificity (optimal cutoff value 1.82 mg/mL). CONCLUSION: DECT performed similarly to 120 kVp-equivalent CT for the diagnosis of bowel ischemia in patients with mechanical SBO. VUE images offer a viable alternative to TUE images for the identification of increased bowel-wall attenuation. Bowel-wall iodine concentration accurately identifies bowel necrosis. KEY POINTS: Question Dual-energy CT (DECT) could detect small-bowel ischemia caused by mechanical small-bowel obstruction (SBO), but its performance is unknown. Findings Reduced bowel-wall enhancement and increased unenhanced bowel-wall attenuation were not significantly different between DECT and 120 kVp-equivalent CT. Bowel-wall iodine concentration identified necrosis with 82% sensitivity and 83% specificity. Clinical relevance DECT performed similarly to 120 kVp-equivalent CT in depicting bowel ischemia in patients with mechanical SBO, while adding quantitative analysis of bowel-wall iodine concentration may further help identify patients requiring surgery.

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