Trends in Renal Stone Clearance after Ureteroscopy: A Review

Background and ObjectivesStone clearance rate in ureteroscopy has varied over the years. This study aims to review the stone clear-ance rate over the last 25 years and assess the change over time. We have analyzed the reasons for the peaks and troughs in stone clearance rate to see if it correlates with any factors such as the introduction of new technology like the holmium laser, flexible ureteroscopy, access sheaths, and digital ureteroscopy. Material and MethodsWe performed a PubMed search (August 2019) for papers including the terms “lithiasis”, “stone clear-ance”, “calculi”, “kidney stone”, “ureteric stone”, “ureteroscopy”, “holmium laser”, “retrorenal surgery” in their title and published between the years 1994 and 2019. The stone size, stone clearance rate and mode of imaging to determine clearance rates were recorded. For data analysis, only prospective studies with a minimum of 50 patients and ureteroscopy arm of prospective randomized controlled trials were included. ResultsWe reviewed 16 papers with a total of 1,689 patients with renal stones. Average stone clearance was 80% and the median stone size was 11.0mm. Stone clearance was determined by either: Computed tomography (CT) scan (8 studies), x-ray alone (3 studies), x-ray and ultrasound (3 studies) or not mentioned (2 studies). CT scan yielded lower stone clearance rates than x-ray due to the increased detail shown on CT. For studies that used absolute clearance with no residual stones, average clearance was 52%, and this stone clearance rate increased as the cut-off size used to determine the stone-free rate was increased.ConclusionThis study highlights that stone clearance rate after ureteroscopy varies significantly amongst different pa-pers because of the stone size used to define ‘stone-free rate’ and the method of imaging used to determine stone clearance. The study also shows that stone clearance rates have not improved significantly over time, despite the introduction of advances in technology.