PRedictive Accuracy of Initial Stone Burden Evaluation.

The current EAU and AUA guidelines still base the recommendations for stone treatment on cumulative stone diameter, a linear measurement of the stone burden. Multiple nomograms rather use the stone burden's surface area to predict post-operative outcomes. More recently, volume has been prposed as the most accurate measure of stone burden and the variable to be reported in stone treatment literature. Although inuitively a three dimensional evaluation is most likely the most accurate representation of the stone burden to be treated.

Several reports however have compared different ways of measuring stone burden and could not confidently identify volume as the most accurate predictor of surgical outcomes.

With this study, we aim to prospectively collect data on a large group of patients that have a pre-operative CT scan available. This imaging will be used to assess the stone burden in different ways, linear, two dimensional and three dimensional. Both procedural and post-operative data will be collected to identify which of the measurements is most accurate in predicting outcomes such as stone free status, operative time and complications such as bleeding. Patients can be included regardless of the procedure that is proposed to treat the stone. After inclusion and after having undergone the procedure, at least one post-operative assessment is necessary to be able to evaluate the pre-operative variables against post-operative outcomes.

Inclusion criteria

• Availability of computed tomography imaging
• Undergoing any of the previously described procedures: extracorporeal shockwave lithotripsy, uretero(reno)scopy or percutaneous nephrolithotomy
• Able to read and understand the information regarding the study and able to provide informed consent

Exclusion criteria

• Under the stated age limit
• No pre-operative computed tomography imaging available