Incremental value of laboratory biomarkers beyond CT findings for detecting bowel ischemia in small bowel obstruction: A Systematic Review

Background: Bowel ischemia is a critical complication of small bowel obstruction (SBO), while computed tomography (CT) is the main imaging test for identifying strangulation and threatened bowel. Laboratory biomarkers offer physiologic information when CT findings are equivocal. In this study we aimed to analyze original articles on the incremental diagnostic value of laboratory biomarkers beyond CT findings for detecting bowel ischemia in SBO. Methods: A systematic review framework consistent with PRISMA 2020 and diagnostic-test-review principles was followed. Eligible studies enrolled adults with SBO, evaluated at least one laboratory biomarker, incorporated CT findings or CT-based classification, and used operative, histopathologic, or clinical outcomes for ischemia, necrosis, strangulation, CT findings or CT-based classification, and used operative, histopathologic, or clinical outcomes for ischemia, necrosis, strangulation, or resection. Results: Fourteen studies were included. Incremental evidence came from combined models incorporating inflammatory or hematologic markers with CT features. A 2026 model increased discrimination from an AUC of 0.88 for selected radiologic features to 0.96 after adding CRP and abdominal guarding. Other integrated models supported contributions from procalcitonin, leukocyte count, CRP, and lactate, while I-FABP and cell-free DNA showed biologic signal without CT-adjusted validation. Biomarker thresholds varied across cohorts, and external validation was limited. Conclusion: Laboratory biomarkers add important information to CT in SBO populations, with the most consistent evidence supporting CRP, procalcitonin, leukocyte-based measures, and lactate. Evidence for formal incremental performance remains limited.