Effect of Stone Composition on Operative Time During Ureteroscopic Holmium:Yttrium-Aluminum-Garnet Laser Lithotripsy With Active Fragment Retrieval

ObjectiveTo assess whether the stone composition affects the operative time of ureteroscopic holmium:yttrium-aluminum-garnet laser lithotripsy (ULL) with active fragment retrieval. The chemical composition of a calculus is known to affect the efficacy with which it is fragmented by a device, such as pneumatic, laser, or shock wave lithotripter. Previous studies examining the efficacy of holmium:yttrium-aluminum-garnet laser lithotripsy have been performed in vitro, but it is not known whether the operative time is significantly affected by the chemical composition of a patient's stone.MethodsWe selected all patients who had undergone ULL for stone disease from July 2008 to January 2011 for a retrospective chart review. We used a standardized operative technique of fragmentation and active retrieval of all fragments identified on full inspection of the entire collecting system using rigid and flexible endoscopes. The stone composition was defined as the presence of a single predominant (>51%) component. Statistical analysis was performed on a per-procedure basis relative to the stone burden, as measured in minutes of operative time per gram of stone.ResultsA total of 187 cases of unilateral ULL with active retrieval of stone fragments confirmed to have a single predominant chemical composition met the inclusion criteria. When accounting for the weight of the recovered stone, no difference was found in the operative time among the apatite, brushite, cystine, calcium oxalate monohydrate, calcium oxalate dihydrate, and uric acid stones.ConclusionAlthough stone composition is widely recognized as an important procedural variable, especially for shock wave lithotripsy, it appears to have little effect on the overall operative time for holmium:yttrium-aluminum-garnet lithotripsy when using active fragment retrieval.