Shock wave lithotripsy correlates with stone density on preoperative computerized tomography

Purpose: We reviewed our experience with the Dornier (R) Doli S lithotriptor to address 2 questions. 1) What is the stone-free rate? 2) Can a stone-free outcome be predicted by preoperative computerized tomography? Materials and Methods: The records of 76 consecutive patients undergoing shock wave lithotripsy for solitary urinary calculi 5 to 20 min in diameter were studied retrospectively. Pretreatment noncontrast computerized tomography was reviewed to determine Hounsfield density. The shock wave lithotripsy outcome was determined at 12 weeks on imaging and categorized as 1) stone free, 2) any residual fragments or 3) stone unchanged. Results: Of the patients 28 (37%) were stone free, 11 (14%) had residual fragments and 37 (49%) had stones that remained unchanged on computerized tomography after a single treatment with shock wave lithotripsy using a Dornier Doli S. Stones of patients rendered stone free had a lower median density compared to stones in patients with residual fragments and unchanged stones (684 vs 1,034 and 920 HU, respectively, p = 0.04). The stone-free rate for stones less than 1,000 HU was 46% vs 17% for stones 1,000 HU or greater (p = 0.01). Conclusions: The combined stone-free and fragmentation rate was 51%, lower than in other published reports. In patients with calculi greater than 1,000 HU shock wave lithotripsy achieved a stone-free rate of only 17%. Patients should be informed of the likelihood of treatment failure or need for auxiliary procedures if the Doli S lithotriptor is used, particularly for stones greater than 1,000 HU.