ULTRASOUND VERSUS COMPUTED TOMOGRAPHY IN THE DIAGNOSIS OF ACUTE APPENDICITIS: A COMPARATIVE REVIEW OF DIAGNOSTIC ACCURACY, IMAGING STRATEGY, AND CLINICAL OUTCOMES

Abstract

Background: Acute appendicitis is the most common surgical emergency of the abdomen, yet its clinical diagnosis remains imprecise. Ultrasonography (US) and computed tomography (CT) are the two dominant cross-sectional imaging modalities used to confirm the diagnosis, but institutions differ markedly in how, and in what sequence, they deploy them. Objective: To synthesize contemporary comparative evidence on the diagnostic accuracy, operational efficiency, and safety of US versus CT — used alone, in combination, or as staged (conditional) strategies — for the diagnosis of acute appendicitis in adolescents and adults. Methods: Five comparative studies published between 2010 and 2025 (one prospective multicenter diagnostic-accuracy study, one prospective single-center cohort, one international two-center retrospective comparison, and two single-center cross-sectional/retrospective analyses; pooled N = 1,772 patients) were identified and analyzed. Data on sensitivity, specificity, positive and negative predictive values, false-positive/negative-appendectomy rates, imaging turnaround time, and CT-utilization were extracted and tabulated for comparison; findings were synthesized narratively and illustrated graphically. Results: CT consistently outperformed US in sensitivity (88-100% vs. 68-91%) and specificity (71-100% vs. 50-98%) across all five studies. A conditional (US-first, CT-only-if-inconclusive) strategy reduced CT utilization by roughly half to five-sixths (17.9-47.2% of imaged patients vs. 100% under an immediate-CT policy) while achieving a sensitivity for appendicitis (95-96%) statistically indistinguishable from an immediate-CT policy, at the cost of a modestly higher false-positive rate (14% vs. 8% in the largest series). US was markedly faster to obtain (median 20-38 minutes) than CT (median 184-194 minutes) and shortened emergency-department length of stay by roughly 90-150 minutes per patient, without ionizing radiation or contrast exposure. Conclusion: A staged, US-first diagnostic pathway with selective (conditional) use of CT for negative or inconclusive ultrasound examinations offers a favorable balance of diagnostic accuracy, radiation stewardship, resource use, and patient throughput, and should be considered the preferred default strategy for suspected acute appendicitis in adults where institutional expertise in appendicular ultrasound is available. CT alone or as a first-line test remains appropriate where US expertise or accessibility is limited, or when a rapid, highly specific diagnosis is clinically imperative.