Diagnostic Accuracy of Non-Contrast CT for Acute Appendicitis in the Emergency Department: A Systematic Review and Meta-Analysis

<i>Background and Objectives:</i> Contrast-enhanced computed tomography (CT) is widely regarded as the gold standard for diagnosing acute appendicitis. However, the use of contrast agents may be contraindicated in patients with renal impairment or a history of allergic reactions. Non-contrast CT (NCCT) offers a potential alternative, but its diagnostic performance has been variably reported across studies. This systematic review and meta-analysis aimed to evaluate the pooled diagnostic accuracy of NCCT in detecting acute appendicitis. <i>Materials and Methods:</i> A comprehensive literature search was conducted across PubMed, Ovid MEDLINE, EMBASE, Cochrane Library, and Google Scholar from inception to June 2025. Studies assessing the diagnostic accuracy of NCCT for acute appendicitis were included. Pooled sensitivity, specificity, and area under the hierarchical summary receiver operating characteristic (HSROC) curve were estimated using a bivariate random-effects model. Study quality was assessed with the QUADAS-2 tool, and publication bias was evaluated using Deeks' funnel plot asymmetry test. <i>Results:</i> Eleven studies comprising 1996 patients met the inclusion criteria. The pooled sensitivity and specificity of NCCT were 0.93 (95% confidence interval; CI, 0.91-0.95) and 0.97 (95% CI, 0.95-0.97), respectively. The area under the HSROC curve was 0.89 (95% CI, 0.83-0.96), indicating moderate diagnostic performance. Heterogeneity was moderate for sensitivity (I² = 48.2%) and substantial for specificity (I² = 77.6%), likely due to differences in study populations and CT acquisition protocols. No significant publication bias was detected (Deeks' test, <i>p</i> = 0.079). <i>Conclusions:</i> NCCT demonstrates moderate diagnostic accuracy for detecting acute appendicitis and offers a practical alternative for patients who cannot receive contrast media. Its safety and rapid applicability make NCCT a useful imaging option in emergency settings, especially when contrast use is limited.