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

Abstract

ObjectivesTo present the national outcomes for New Zealand of over 9 000 stone cases treated with SWL at 21 centres over a 20 year period. Subjects/patients and methodsStone 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 ≤4mm. Secondary outcomes were stone free rate, complications and auxiliary procedures, and all statistical analyses were descriptive. Results9 538 stone cases (7 769 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 ≤4mm. 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. ConclusionSWL 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. KeywordsKidney stones, Nephrolithiasis, Lithotripsy IntroductionUrolithiasis comprises a significant and growing proportion of urological practice, with international epidemiological data demonstrating a global increase in its incidence and prevalence in recent decades [1][2][3]. This has important economic implications for healthcare services: a recent analysis estimated that the cost of stone disease will be >$5 billion per annum by 2030 in the USA [4]. Since its inception in the 1980s, shock wave lithotripsy (SWL) has become a well established treatment option for urolithiasis, demonstrating superior outcomes in morbidity and postoperative recovery than surgery, with relatively few contraindications [5,6]. The European Association of Urology (EAU) guidelines recommend SWL as the first line management option for proximal ureteral stones <10mm, and an equivalent first line option to endourology for renal stones <20mm, proximal ureteral stones >10mm and distal ureteral stones <10mm [7]. In spite of this, reports indicate that the rate of SWL use has plateaued or decreased in recent years alongside a surge in the use of ureteroscopy with the holmium laser [8][9][10][11], and despite evidence suggesting similar success rates between management options [7]. The current evidence examining the use of SWL demonstrates wide variation in clinical outcomes, with overall stone free rates (SFRs) ranging from 40.2% to 96.8%, and is limited to studies reporting small coho...

Current ESWL practice and outcomes in the UK: A multicentre snapshot

“…The current study also confirms the current understanding that SWL outcomes are inversely proportional to stone size, 10 with success rates decreasing from 65% for those under 5 mm, to 50% for those stones greater than 15 mm. A lack of data on stone composition, including those with, for example, cystine urolithiasis, prevents any comment on the use of SWL for such patient groups.…”

“…9 However, other large multicentre studies have shown similar low SFRs, with 45% SFRs in over 9000 cases treated at multiple centres in New Zealand. 10 There may be several reasons both for this discrepancy and the variability between centres investigated in this study. The first is the method of follow-up undertaken to determine SFRs and the nomenclature used to define it when comparing results from this study and those in the published literature.…”

“…A recent multicentre study has shown SFRs in different locations in the kidney can vary from that expected in the literature, and, for example, can be higher for lower pole stones, with rates between 61% and 66% for stones under 10 mm, dependent on size, than for stones elsewhere in the kidney. 10 Stone location is also important when considering success following SWL treatment for ureteric stones: A meta-analysis 16 found SFRs of 82% following SWL to stones in the proximal ureter, 73% in the mid-ureter, and 74% in the distal ureter. In addition, SFRs were lower for ureteric stones >10 mm in diameter when managed with SWL.…”

“…9 Outcomes based on several centres are less commonly published, but a recent publication from a national SWL database in New Zealand suggest stone-free rates (SFRs) of 45%. 10 Factors shown to affect outcome are stone size and composition including Hounsfield Units, stone location, skin to stone distance, body mass index (BMI) of the patient, and the presence of abnormal renal anatomy. 11,12 In addition, outcomes are also thought to be influenced by treatment protocol and experience of the operator in administering SWL.…”

Comparison of safety and outcomes of shock wave lithotripsy between elderly and non-elderly patients

“…A large national SWL database in New Zealand showed that common post-SWL complications included pain managed with intravenous or suppository analgesics (5.9%), perinephric hematoma (0.2%), urinary tract infection (1.1%), urosepsis (0.04%), and hospital admission (6.8%) 13. In the present study, the elderly group had a higher complication rate than the non-elderly group (23.8% vs 15.5%, P <0.05).…”