A key point emerging from our review is the clear advantage of three-dimensional (3D) volume determination over one-dimensional diameter measurements. While formula-based methods can be sufficient for small, regularly shaped stones, they tend to overestimate the true volume in larger or irregular calculi. In contrast, software-assisted 3D segmentation substantially improves measurement accuracy and reproducibility, minimizing operator variability. Artificial intelligence (AI)-driven solutions further streamline this process by automating segmentation and analysis in near-real time. Additionally, AI-based volumetric assessment further minimizes inter-observer variability.
NCCT is the gold standard for measuring kidney stone volume, although technical factors such as slice thickness, kernel settings, and patient body habitus can affect measurement precision. Alongside NCCT, alternative imaging methods like magnetic resonance imaging and ultrasound hold promise for volumetric stone assessment; however, the available data on their volumetric accuracy remains limited.
Clinically, multiple studies have shown that stone volume is a superior predictor of stone-related events during follow-up, spontaneous stone passage under conservative management, and stone-free rates after shockwave lithotripsy and ureteroscopic stone treatment. While volume measurement does not outperform diameter for percutaneous nephrolithotomy outcomes, it nonetheless offers a more holistic view of overall stone burden.
Looking ahead, the incorporation of standardized volume measurement protocols and AI-based segmentation tools into daily practice could substantially improve patient stratification and personalized treatment planning. As endourologists, we believe that embracing volumetric measurements will ultimately lead to better outcomes for patients with kidney stone disease.
Written by:
- Nico C. Grossmann, MD, Department of Urology, University Hospital Southampton NHS Trust, Southampton, UK; Department of Urology, Kantonsspital Luzern, Lucerne, Switzerland
- Bhaskar K. Somani, MRCS, FEBU, FRCS(Urol), Department of Urology, University Hospital Southampton NHS Trust, Southampton, UK.