Abstract
Objective: To compare the diagnostic performance of ultrasonography (US) and non-contrast low-dose computed tomography (LDCT) in patients with suspected acute appendicitis (AA) in Duhok, Iraq.
Methodology: This prospective paired diagnostic-accuracy study included 150 patients who underwent both US and LDCT between February and November 2025. Histopathology following appendectomy served as the reference standard. Diagnostic accuracy measures were calculated. Results: Of 150 patients, 93 (62.0%) underwent appendectomy, with histopathology confirming AA in 85 and excluding it in eight. US demonstrated sensitivity of 35.3%, specificity of 50.0%, positive predictive value (PPV) of 88.2%, negative predictive value (NPV) of 6.8%, and accuracy of 36.6%. Corresponding LDCT values were 69.4%, 100%, 100%, 23.5%, and 72.0%, respectively. LDCT showed significantly higher sensitivity and overall accuracy than US (McNemar p<0.001 for both). However, the specificity difference was not statistically significant (P=0.125).
Conclusion: Non-contrast LDCT demonstrated superior sensitivity and diagnostic accuracy compared with US among histopathologically verified patients. However, partial verification bias, limited histopathology-negative cases, non-blinded interpretation, and inclusion of children restrict generalizability. LDCT may serve as a second-line imaging modality following negative, equivocal, or nondiagnostic US rather than replacing US as the initial investigation.

Key words: Ultrasonography, low dose computed tomography, acute appendicitis.