Diagnostic Performance of Individual CT Signs for Identifying Ischemia and Necrosis in Small Bowel Obstruction: A Systematic Review and Meta-Analysis Le Corre P, Youinou M, Chatellier G, Zins M AJR Am J Roentgenol. Published online April 29, 2026. doi:10.2214/AJR.26.34714
Small bowel obstruction (SBO) is a frequent cause of emergency department admission and a major indication for urgent abdominal surgery. Approximately 10-20% of SBO cases have associated bowel ischemia [1], which may rapidly progress to transmural necrosis requiring bowel resection and is associated with mortality rates approaching 40% [1,2]. Ischemia and necrosis represent distinct stages within the clinical spectrum of bowel injury, and their differentiation remains clinically critical given the substantial implications for surgical management and patient outcomes. Reversible ischemia may allow simple adhesiolysis with bowel preservation, whereas irreversible transmural necrosis typically mandates bowel resection [2]. Accordingly, early identification of the transition to necrosis is critical for determining surgical urgency and guiding operative management. In this emergency setting, multidetector CT (MDCT) plays a pivotal role in the early and accurate detection of imaging findings suggestive of bowel ischemia in patients with SBO, with reported pooled specificity and sensitivity of 92-95% and 82%, respectively [3,4]. Several imaging findings associated with bowel ischemia have been described [3-5]; however, the diagnostic performance of CT signs specifically for transmural bowel necrosis has not yet been systematically investigated. In this study, the authors conducted a systematic review and meta-analysis to evaluate the diagnostic performance of individual CT signs for detecting surgically confirmed bowel ischemia and transmural necrosis in patients with SBO. The meta-analysis included 19 retrospective single-center studies from tertiary-care institutions, comprising a total of 2453 patients with 2489 episodes of SBO diagnosed at CT or surgery. Fourteen studies evaluated CT findings for bowel ischemia using surgical and/or pathologic confirmation as the reference standard, with seven studies also relying on uneventful follow-up to confirm absence of ischemia in patients who did not undergo surgery. Eight studies evaluated CT findings for transmural necrosis. Ischemia and transmural necrosis were identified in 30% and 37% of episodes, respectively. A total of 14 CT signs for ischemia and 11 for transmural necrosis were selected for evaluation in the meta-analysis. Pooled sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were calculated for each finding. CT signs were considered predictive when both pooled specificity exceeded 85% and DOR exceeded 10. Study quality was assessed using the QUADAS-2 tool, and interreader agreement was evaluated through pooled kappa statistics. Four CT signs were identified as predictive of bowel ischemia. Among these, increased unenhanced bowel wall attenuation showed the highest specificity of 98% although with relatively low sensitivity (36%) (DOR: 30.5; PLR: 19.30; NLR: 0.65). Reduced bowel wall enhancement also demonstrated high specificity (92%) and strong diagnostic performance (DOR: 15.8; PLR: 7.45; sensitivity: 55%; NLR: 0.48). Closed-loop configuration showed the highest sensitivity (75%) (specificity: 85%, DOR: 19.60; PLR: 5.25; NLR: 0.30), whereas diffuse mesenteric haziness demonstrated comparable diagnostic performance (specificity:89%; DOR: 22.30; PLR: 6.78; sensitivity: 72%; NLR 0.31). Eleven of the 14 signs were evaluated for necrosis. Importantly, increased unenhanced bowel wall attenuation emerged as the only CT sign predictive of bowel necrosis (specificity: 92%; sensitivity: 55%; DOR: 18.0; PLR 8.75%, sensitivity: 55%; NLR: 0.49). These results support consideration of noncontrast acquisition in routine CT protocols for SBO evaluation, particularly in patients at high risk for strangulation or ischemic compromise. Other signs, including reduced bowel wall enhancement, diffuse mesenteric haziness, closed-loop configuration, and pneumatosis /venous gas, demonstrated limited diagnostic performance. Most CT findings, including all of the predictive signs, demonstrated substantial interreader agreement, whereas mesenteric findings such as mesenteric edema and venous engorgement showed only moderate agreement, likely reflecting their subjective interpretation and the lack of consistently standardized definitions across studies. The predictive signs all had suboptimal sensitivity for their respective endpoints. Indeed, none of the individual signs had sufficiently low NLR to reliably exclude ischemia or necrosis. Assessment of multiple concurrent imaging findings may therefore help reduce false-negative diagnoses. Future predictive models integrating multiple imaging findings, clinical and laboratory parameters may further improve risk stratification and surgical decision-making. Limitations include the retrospective design of all included studies, as well as potential selection bias related to the high prevalence of surgery, ischemia, and necrosis in tertiary-care hospital cohorts, which may limit generalizability to lower-risk populations. Additional limitations include substantial interstudy heterogeneity for some CT findings, variability in reference standards, and differences in the interval between imaging and surgery. In conclusion, four CT signs were identified as predictive of bowel ischemia in patients with SBO, whereas increased unenhanced bowel wall attenuation emerged as the only finding also predictive of necrosis, supporting the potential value of noncontrast acquisition in routine SBO CT protocols. Although no individual CT finding demonstrated sufficient sensitivity to reliably exclude ischemia or necrosis, recognition of these key imaging features may help guide surgical decision-making in patients with SBO. | References
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