The Cumulated Stone Diameter: A Limited Tool for Stone Burden Estimation

Area of Science:

• Urology
• Medical Imaging
• Nephrology

Background:

• Accurate preoperative estimation of kidney stone burden is crucial for successful retrograde intrarenal stone surgery (RIRS).
• Standardization of stone burden assessment methods is needed to improve patient outcomes.

Purpose of the Study:

• To compare the performance of three main methods for estimating kidney stone burden.
• To identify the most effective method for preoperative evaluation in RIRS.

Main Methods:

• Prospective evaluation of 142 patients undergoing RIRS from January 2012 to June 2013.
• Pre- and postoperative CT scans were used to estimate stone burden via cumulative stone diameter (M1), Ackermann's formula (M2), and sphere formula (M3).
• Comparison of the predictive value of each method for postoperative stone-free status.

Main Results:

• The overall stone-free rate was 64%.
• All three methods (M1, M2, M3) predicted stone-free status for stones <20 mm.
• For stones >20 mm, Ackermann's formula (M2) and the sphere formula (M3) were significant predictors, with M3 showing independent association in multivariate analysis.

Conclusions:

• Kidney stone burden estimation is a key predictor of RIRS outcomes.
• For stones <20 mm, M1, M2, and M3 provide accurate estimations.
• For stones >20 mm, volume calculation using the sphere formula (M3) is recommended for improved prediction of stone-free status.