Effect of Slice Thickness on the Diagnostic Accuracy of Non-Contrast CT KUB for Renal Stone Detection

Abstract

Background: Non-contrast computed tomography of the kidneys, ureters, and bladder is the reference imaging modality for suspected urinary tract calculi, but its diagnostic performance may vary according to reconstruction slice thickness. Objective: To evaluate the effect of 1 mm, 3 mm, and 5 mm axial slice thicknesses on renal stone detection, stone visibility, image noise, and radiologist diagnostic confidence in non-contrast CT KUB. Methods: This comparative cross-sectional study included 109 patients aged 18–70 years who underwent non-contrast CT KUB for suspected renal or ureteric stones. Raw CT datasets were reconstructed into 1 mm, 3 mm, and 5 mm axial series and reviewed in randomized order by a blinded radiologist. Stone detection, visibility score, perceived image noise, and diagnostic confidence were recorded. Chi-square testing, one-way ANOVA, and logistic regression were used for analysis. Results: Stone detection was highest on 1 mm slices (81.7%), followed by 3 mm (75.2%) and 5 mm slices (63.3%; p = 0.004). Good visibility declined from 73.4% at 1 mm to 32.1% at 5 mm, while high diagnostic confidence decreased from 56.9% to 11.9% (both p < 0.001). Compared with 1 mm slices, 5 mm slices showed significantly lower odds of stone detection (OR = 0.40, 95% CI: 0.23–0.70; p = 0.002). Conclusion: Thin-slice 1 mm reconstruction improves renal stone detection, visibility, and diagnostic confidence on non-contrast CT KUB, despite higher perceived image noise