Measuring kidney stone volume - practical considerations and current evidence from the EAU endourology section

This narrative review provides an overview of the use, differences, and clinical impact of current methods for kidney stone volume assessment.

The different approaches to volume measurement are based on noncontrast computed tomography (NCCT). While volume measurement using formulas is sufficient for smaller stones, it tends to overestimate volume for larger or irregularly shaped calculi. In contrast, software-based segmentation significantly improves accuracy and reproducibility, and artificial intelligence based volumetry additionally shows excellent agreement with reference standards while reducing observer variability and measurement time. Moreover, specific CT preparation protocols may further enhance image quality and thus improve measurement accuracy. Clinically, stone volume has proven to be a superior predictor of stone-related events during follow-up, spontaneous stone passage under conservative management, and stone-free rates after shockwave lithotripsy (SWL) and ureteroscopy (URS) compared to linear measurements.

Although manual measurement remains practical, its accuracy diminishes for complex or larger stones. Software-based segmentation and volumetry offer higher precision and efficiency but require established standards and broader access to dedicated software for routine clinical use.