Shock wave lithotripsy (SWL): outcomes from a national SWL database in New Zealand

Abstract

Objectives: To present the national outcomes for New Zealand of over 9000 stone cases treated with SWL at 21 centres over a 20 year period.

Subjects/patients and methods: Stone cases treated with SWL on board the Mobile Medical Technology (MMT) vehicle between 19 June 1995 and 1 December 2014 were identified, and data collection undertaken prospectively for patient, stone and treatment characteristics, and retrospectively for treatment outcomes. The primary outcome was treatment success, defined as complete stone clearance or clinically insignificant residual fragments (CIRFs) of ≤4 mm. Secondary outcomes were stone free rate, complications and auxiliary procedures, and all statistical analyses were descriptive.

Results: 9538 stone cases (7769 patients) were included. The overall, cumulative success rate was 58.7%; this included 45.1% that were stone free and 13.5% in which there were CIRFs ≤4 mm. Success rates varied widely by stone size and location. Overall rates of urinary tract infection, perinephric haematoma, hospital admission and ureteral stent placement were 1.1%, 0.2%, 6.8% and 4.1%, respectively. Variations in SWL protocols across centres limits the overall reliability of our findings.

Conclusion: SWL remains a low morbidity management option requiring careful patient selection. This study provides valuable data for patient counseling and the formation of evidence based guidelines in SWL. The MMT SWL service has demonstrated that is it possible to deliver a high volume specialist stone service without requiring patients to travel further for treatment.

Keywords: Kidney stones; Lithotripsy; Nephrolithiasis.