Diagnostic Accuracy of CT, Ultrasound, and Clinical Scoring in Differentiating Acute Appendicitis from Gastrointestinal Mimickers

Abstract

Background: Acute appendicitis is one of the most common surgical emergencies; however, differentiating it from gastrointestinal mimickers remains a clinical challenge, particularly in resource-limited settings.

Objective: To evaluate and compare the diagnostic accuracy of computed tomography (CT), ultrasonography (US), and clinical scoring systems in differentiating acute appendicitis from gastrointestinal mimickers.

Methods: This prospective cross-sectional diagnostic accuracy study was conducted at department of surgery indus medical college, Tando Muhammad Khan from 1st February 2025 to 31st January 2026, included 231 consecutive patients presenting with suspected acute appendicitis. Clinical assessment was performed using the Alvarado and Appendicitis Inflammatory Response (AIR) scores. All patients underwent ultrasonography, while CT was performed in cases with inconclusive or discordant findings.

Results: Acute appendicitis was confirmed in 156 (67.5%) patients, while 75 (32.5%) were diagnosed with gastrointestinal mimickers. The Alvarado score demonstrated sensitivity of 82.7% and specificity of 64.0%, whereas the AIR score showed sensitivity of 85.3% and specificity of 69.3%. Ultrasonography achieved sensitivity of 87.2%, specificity of 72.0%, and overall accuracy of 82.7%. CT demonstrated the highest diagnostic performance with sensitivity of 95.5%, specificity of 90.0%, overall accuracy of 93.3%, and AUC of 0.94. The negative appendectomy rate was 8.8%.

Conclusion: CT scan showed superior diagnostic accuracy in differentiating acute appendicitis from gastrointestinal mimickers, followed by ultrasound. Clinical scoring systems were effective for initial risk stratification but insufficient as standalone diagnostic tools.