Shockwave Lithotripsy Practice Pattern Variations Among and Between American and Canadian Urologists: In Support of Guidelines

Abstract

Purpose:

Shockwave lithotripsy (SWL) is a widely utilized form of treatment for urolithiasis. There are new evidence-based recommendations regarding pre-SWL patient work-up and the performance of SWL. The purpose of this study is to determine practice patterns for SWL and to determine if regional variation exists between Canada and the United States.

Materials and Methods:

A 19-question survey was prepared. Canadian urologists were surveyed through e-mail correspondence. In the United States, members of the Endourologic Society and members of two large stone management groups were surveyed. Canadian and American results were compared using the chi-square and Fisher's exact tests.

Results:

Ninety-four Canadian urologists and 187 U.S. urologists completed the survey. Practice patterns differed between countries. Intravenous sedation was more commonly used in Canada (Canada 94.7% vs United States 17.9%, p < 0.001); routine antibiotics were more commonly given in United States (Canada 2.1% vs United States 78.1%, p < 0.001); a shock rate of 2 Hz was more common in Canada (Canada 76.6% vs United States 16.2%, p < 0.00001); rate of discontinuing ASA for renal and ureteral stone treatment was higher in the United States (renal Canada 88.3% vs United States 95.7%, p < 0.02; ureteral Canada 62.4% vs 90.3%, p < 0.0001); and ureteral stents were more commonly used if treating a large stone or patients with solitary kidneys in the United States (large stones Canada 58.2% vs United States 88.8%, p = 0.0001; solitary kidney Canada 50.6% vs 66.3%, p = 0.02).

Conclusions:

This study highlights the absence of standardization of SWL. Significant regional differences exist in practice patterns and performance of SWL between Canadian and American urologists.

Introduction

Shockwave lithotripsy (SWL) was introduced for the treatment of urolithiasis in the 1980s¹ and has become a commonly used minimally invasive treatment modality for renal and ureteral stones. In the 1990s, SWL accounted for 51% to 54% of procedures for stone treatment in the United States.² Recent reports have documented an increase in the use of ureteroscopy and laser lithotripsy for the treatment of ureteral and renal stones with a decreased use of SWL.³ SWL is still, however, an important first line treatment for stone disease. SWL outcomes are highly variable and depend upon numerous factors such as patient and stone characteristics, the technical performance of SWL, follow-up imaging modality utilized, the number of treatments on a given stone, and the definition of treatment “success” (i.e.: stone free vs so-called “insignificant fragments”). Previous guidelines regarding the use of SWL for the treatment of urolithiasis exist from both the European Association of Urology (EAU) and the American Urological Association (AUA)^4
–6; however, these guidelines cover the indications for SWL in the treatment of urolithiasis. The AUA's “White Paper” outlines current perspectives in the safety of SWL.⁷ More recently, the EAU has published guidelines regarding the performance of SWL.⁸

This study was performed to identify Canadian and American practice patterns with respect to the preprocedural work-up and performance of SWL to determine if lithotripsy centers in Canada and the United States utilize similar treatment strategies. The secondary aim was to investigate the technical performance of SWL and the incorporation of evidence for optimal SWL performance at SWL centers in Canada and the United States. We hypothesize that there is great variability in the technical performance of SWL in both countries and wish to raise the question: are best practice guidelines for SWL supported to optimize treatment outcomes, minimize patient morbidity and, subsequently, minimize costs to our healthcare systems?

Materials and Methods

This study utilized a 19-question survey (Fig. 1). The survey covered three main domains of SWL: the preprocedural work-up of the patient, the technical performance of SWL (e.g.: shock power, number, and rate of delivery), and measures taken to prevent complications (e.g.: holding antiplatelet medications, use of stents, and antibiotic usage). The survey was administered to Canadian urologists at each of the 16 stationary lithotripsy units in Canada. American urologists working with two large mobile lithotripter partnerships (Midwest Stone Management, Fortec Lithotripsy) were surveyed using paper surveys and members of the Endourologic Society were surveyed using SurveyMonkey^®.

FIG. 1.

SWL practice pattern survey. SWL = shockwave lithotripsy.

Responses from Canadian and American urologists' were compared using Fisher's exact test or chi-square test as indicated. All statistical analyses were performed using SAS version 9.2 software (SAS Institute, Inc., Cary, NC).

Results

A total of 97 Canadian urologists from 16 centers and 187 American urologists completed the survey. Sixty-seven percent of Canadians surveyed were in academic practice. Approximately 30 percent of American urologists surveyed were in academic practice.

Canadian results

Sixty-two percent (10/16) of Canadian centers perform electrocardiograms (ECGs) before SWL based on an age-based cut-off for those with no cardiac risk factors, with a median age of 50 years or older to have a routine ECG. Other centers would perform ECGs in patients with a history of hypertension (31%), history of coronary artery disease (50%), arrhythmia (56%), or “medically complex” patients (6%) regardless of age.

Fifty-one percent of centers routinely perform a urine culture to screen for asymptomatic bacteriuria before SWL, and only 2% of Canadian urologists surveyed routinely used prophylactic antibiotics before SWL. Ninety-five percent use intravenous sedation/analgesia during SWL (instead of general anesthesia) and 68% routinely have an anesthetist present during treatment.

Gating (delivery of shockwaves during the refractory period of the cardiac cycle) was reported to be used by 78% of urologists in Canada if treatment was causing arrhythmia, but it was not used routinely. The majority, 76%, of Canadian urologists routinely use a shock rate of 2 Hz (120 shockwaves/min), while 26% use a rate of 1.5 Hz, and 16% routinely use 1 Hz. There was some variability in shock rate with some urologists decreasing from 2 to 1.5 Hz for stones larger than 1 cm. For renal stones, most (64%) urologists stopped treatment at a max of 3000 shocks; for ureteral stones, 69% halt at 3000 shocks and 29% go as much as 3500 to 4500 shocks.

Eighty-eight percent and 62% of Canadian urologists routinely hold acetylsalicylic acid (ASA) before treatment of renal stones and ureteral stones, respectively. Fifty-one percent will routinely stent patients with solitary kidneys before SWL and 58% will stent patients with large stones (typically with a cut-off of >1.5 cm).

American results

Forty-nine percent of American urologists reported that an ECG was performed before SWL with a median age of 50 years or older receiving an ECG. Regardless of age, the percentage of respondents reporting that an ECG is performed before SWL if the patient had a history of hypertension was 31%, coronary artery disease, 59%, and arrhythmia, 59%.

Seventy-eight percent of American urologists reported using routine prophylactic antibiotics. Intravenous sedation was used by 17.9% of American urologists with the vast majority (82%) performing SWL under general anesthesia; 98% of American urologists reported having an anesthetist present during SWL.

Gating was reported to be used by 12% of American urologists routinely and by 73% if an arrhythmia developed during treatment. Sixteen percent of American urologists routinely use a shock rate of 2 Hz, 45% use a rate of 1 Hz, and 41% reported using a rate between 1 and 1.5 Hz (typically 1.5 Hz or 90 shockwaves per minute), with some respondents reporting lowering the rate depending on the size of the stone. The number of shocks delivered was generally greater for mid/distal ureteral stones with a median of 3000 shocks vs a median of 2800 shocks for stones in the kidney/proximal ureter. Twenty-four percent and 40% would go above 3000 shocks in the kidney/proximal ureter and mid/distal ureter, respectively.

Ninety-six percent of American urologists routinely hold ASA before SWL for renal stones; 90% hold ASA for ureteral stones. Sixty-six percent of American urologists will stent patients with solitary kidneys and 89% will stent patients with large stones, with a median size to stent of 1.3 cm.

Variation Between Canada and United States

Table 1 summarizes differences between Canadian and American urologists.

Table 1.

Variation Between Canadian and American Shockwave Lithotripsy Practice Patterns

	Canada %	United States %	p-Value
IV sedation	94.7	17.9	<0.001^a
Routine urine C + S	51.1	55.2	0.51^a
Routine antibiotics	2.1	78.1	<0.0001^b
Shock rate of 60	16	45.4	<0.0001^a
Shock rate of 120	76.6	16.2	<0.0001^a
Dose escalation	100	87.4	0.0004^b
Stop aspirin for renal stones	88.3	95.7	0.02^a
Stop aspirin for ureteral stones	62.4	90.3	<0.0001^a
Stent solitary kidney	50.6	66.3	0.02^a
Stent large stones	58.2	88.8	<0.0001^a

Chi-square test.

Fisher's exact test.

C+S = culture and sensitivity; IV = intravenous.

Discussion

SWL is a commonly used stone treatment; until recently, there was a relative absence of evidence-based guidelines regarding the performance of SWL. The recent EAU guidelines are evidence based and may be helpful in standardizing SWL treatment.⁸ Our study found that there was considerable variability among urologists regarding the performance of SWL with variability between countries as highlighted in Table 1.

Both the AUA and EAU guidelines recommend screening for asymptomatic bacteriuria before any stone treatment; however, we found that only 51% of Canadian urologists and 55% of American urologists use urine cultures before SWL. Screening for asymptomatic bacteriuria may be underrepresented in this survey as some centers screen with urinary dipstick or urinalysis and not urine cultures in all cases. The AUA guidelines for antibiotic use were updated in 2008 to discontinue recommendation of routine prophylactic antibiotics during SWL.⁹ This recommendation appears to have been adopted by Canadian urologists with only 2% using routine antibiotics; however, 78% of surveyed American urologists reported using routine antibiotics.

The 2007 AUA Urolithiasis Guidelines state that SWL is useful for patients “desiring minimal anesthesia”⁵ since SWL can be performed using intravenous sedation and analgesia protocols instead of general or regional anesthesia utilized for ureteroscopy or more invasive stone treatments. However, the vast majority, 82% of surveyed American urologists use general anesthesia routinely for SWL compared with only 5% of Canadian urologists. There are, however, potential benefits of SWL under general anesthesia with increased treatment success rates because of decreased patient motion.^10,11

All Canadians used a dose escalation protocol, compared with 87% of Americans. Dose escalation protocols have been theorized to decrease the risk of renal damage during SWL,^12,13 which has been shown in animal models with variable clinical results as outlined in the review by McClain and associates.¹⁴

There is evidence that if SWL is performed while a patient is on antiplatelet medications (ASA and clopidogrel), there may be increased risk of bleeding complications such as subcapsular or perinephric hematomas.^15

–19 Rates of performance of SWL while patients are on antiplatelets were higher in Canada compared with the United States with 88% of Canadian urologists discontinuing ASA for renal stones vs 96% of American urologists. Treatment on nonsteroidal anti-inflammatory drugs (NSAIDs) was more common with 62% of Canadians and 85% of Americans holding NSAIDs before treatment of renal stones. NSAIDs are used at some centers, typically outside North America, in SWL analgesia protocols.^20

–23

SWL efficacy is improved when delivered at a slower shock rate (i.e.: 1–1.5 Hz) compared with 2 Hz. There are randomized controlled trials supporting this for both renal and ureteral stones,^24,25 which have been confirmed by meta-analyses.^26,27 The cost-effectiveness of SWL is also improved when a slower shock rate is utilized because of improved stone fragmentation.²⁸ Despite this evidence, 76% of Canadian urologists routinely use a rate of 2 Hz. Only 16% of American urologists routinely reported using 2 Hz, with 45% using a rate of 1 Hz and another 41% using a rate between 1 and 1.5 Hz. The drawback of slower shock rate is increased treatment time.

Stents are typically used before SWL to relieve symptomatic obstruction, in cases of infection, or are inserted prophylactically in an attempt to prevent Steinstrasse and post-SWL complications. However, stents may decrease the clearance of stone fragments after SWL.²⁹ There are cases where pre-SWL stenting may be desired to prevent obstruction—namely solitary kidneys and patients with large stones. Fifty-one percent of Canadian urologists would routinely stent a patient with a solitary kidney vs 66% of American urologists and 58% of Canadian urologists reported routinely stenting patients with large stones vs 89% of American urologists.

This study is limited by its nature as a survey and the differing administration between the Canadian and American groups. The response rate in Canada was excellent (94%); however, the U.S. data were determined by multiple methods, including Endourologic Society survey, and by surveying members of two large stone treatment groups in the United States. As such, no true sample size was calculated for a response rate for urologists in the United States. The results may not be generalizable to all urologists across the United States. The Canadian group also had higher respondents in academic practice (67% of Canadians surveyed vs 30% of Americans surveyed). However, despite more Canadians being in academic practice, Canadians did not follow all evidence-based best practices such as using a lower shock rate of 1 to 1.5 Hz. Despite these limitations, our study suggests that there are significant variations in the performance of SWL between Canada and the United States, including some practice patterns that may result in less than optimal treatment outcomes or potential increased risk for complications. There has been an absence of Canadian guidelines regarding performance of SWL; however, recently published guidelines for treatment of ureteral stones includes some information on improving SWL outcomes.³⁰

Conclusions

This study found that there are statistically significant differences in SWL practice patterns in Canada compared with the United States, based on survey responses. American urologists who were more likely to use general anesthesia with routine prophylactic antibiotics, at a slower shock rate, were more likely to stent patients with solitary kidneys or large stones and were less likely to treat patients on ASA compared with Canadian urologists. We believe this study supports the use of evidence-based guidelines to standardize pre-SWL work-up and the technical performance of SWL to maximize patient outcomes and minimize potential morbidity and complications.

Footnotes

Acknowledgments

The study authors acknowledge the Endourologic Society, as well as the Midwest Stone Management and Fortec Lithotripsy, with dissemination of the survey to the American respondents.

Author Disclosure Statement

Dr. Honey discloses a financial relationship with Cook Medical. Dr. Pace discloses a financial relationship with Cook Medical. None of these relationships poses a conflict of interest for this research. Drs. Lantz, McKay, Ordon, and Monga have no disclosures.

Abbreviations Used

References

Chaussy

, Brendel

, Schmiedt

. Extracorporeally induced destruction of kidney stones by shock waves. Lancet, 1980; 2:1265–1268.

Pearle

, Calhoun

, Curhan

, et al. Urologic diseases in America project: Urolithiasis. J Urol, 2005; 173:848–857.

Ordon

, Urbach

, Mamdani

, et al. The surgical management of kidney stone disease: A population based time series analysis. J Urol, 2014; 192:1450–1456.

Tiselius

, Ackermann

, Alken

, et al. Guidelines on urolithiasis. Eur Urol, 2001; 40:362–371.

Preminger

, Tiselius

, Assimos

, et al. 2007 Guideline for the management of ureteral calculi. Eur Urol, 2007; 52:1610.

Preminger

, Assimos

, Lingeman

, et al. Chapter 1: AUA guideline on management of staghorn calculi: Diagnosis and treatment recommendations. J Urol, 2005; 173:1991–2000.

American Urological Association Education and Research, Inc. Current perspective on adverse effects in shock wave lithotripsy. 2009. Available at: http://www.auanet.org/common/pdf/practices-resources/quality/white-papers/whitepaper.pdf (accessed June 28, 2016 ).

Turk

, Petrik

, Sarica

, et al. EAU guidelines on interventional treatment for urolithiasis. Eur Urol, 2016; 69:475–482.

Wolf

Jr. , Bennett

, Dmochowski

, et al. Best practice policy statement on urologic surgery antimicrobial prophylaxis. J Urol, 2008; 179:1379–1390.

10.

Eichel

, Batzold

, Erturk

. Operator experience and adequate anesthesia improve treatment outcome with third-generation lithotripters. J Endourol, 2001; 15:671–673.

11.

Sorensen

, Chandhoke

, Moore

, et al. Comparison of intravenous sedation versus general anesthesia on the efficacy of the Doli 50 lithotriptor. J Urol, 2002; 168:35–37.

12.

Willis

, Evan

, Connors

, et al. Prevention of lithotripsy-induced renal injury by pretreating kidneys with low-energy shock waves. J Am Soc Nephrol, 2006; 17:663–673.

13.

Connors

, Evan

, Blomgren

, et al. Effect of initial shock wave voltage on shock wave lithotripsy-induced lesion size during step-wise voltage ramping. BJU Int, 2009; 103:104–107.

14.

McClain

, Lange

, Assimos

. Optimizing shock wave lithotripsy: A comprehensive review. Rev Urol, 2013; 15:49–60.

15.

Bahceci

, Tuzcu

, Akay

, et al. Serious clopidogrel associated renal hematoma in a type 2 diabetic patient with primary hyperparathyroidism after extracorporeal shock wave lithotripsy. Saudi Med J, 2005; 26:1007–1009.

16.

Knorr

, Woodside

. Large perirenal hematoma after extracorporeal shock-wave lithotripsy. Urology, 1990; 35:151–153.

17.

Razvi

, Fuller

, Nott

, et al. Risk factors for perinephric hematoma formation after shockwave lithotripsy: A matched case-control analysis. J Endourol, 2012; 26:1478–1482.

18.

Ruiz

, Saltzman

. Aspirin-induced bilateral renal hemorrhage after extracorporeal shock wave lithotripsy therapy: Implications and conclusions. J Urol, 1990; 143:791–792.

19.

Sare

, Lloyd

, Stower

. Life-threatening haemorrhage after extracorporeal shockwave lithotripsy in a patient taking clopidogrel. BJU Int, 2002; 90:469.

20.

Akcali

, Iskender

, Demiraran

, et al. Randomized comparison of efficacy of paracetamol, lornoxicam, and tramadol representing three different groups of analgesics for pain control in extracorporeal shockwave lithotripsy. J Endourol, 2010; 24:615–620.

21.

Mezentsev

. Meta-analysis of the efficacy of non-steroidal anti-inflammatory drugs vs. opioids for SWL using modern electromagnetic lithotripters. Int Braz J Urol, 2009; 35:293–297.

22.

Ozkan

, Erdemir

, Erkorkmaz

, et al. Comparison of three different analgesic protocols during shockwave lithotripsy. J Endourol, 2012; 26:691–696.

23.

Tokgoz

, Yurtlu

, Hanci

, et al. Comparison of the analgesic effects of dexketoprofen and diclofenac during shockwave lithotripsy: A randomized, double-blind clinical trial. J Endourol, 2010; 24:1031–1035.

24.

Pace

, Ghiculete

, Harju

, et al. Shock wave lithotripsy at 60 or 120 shocks per minute: A randomized, double-blind trial. J Urol, 2005; 174:595–599.

25.

Honey

, Schuler

, Ghiculete

, et al. A randomized, double-blind trial to compare shock wave frequencies of 60 and 120 shocks per minute for upper ureteral stones. J Urol, 2009; 182:1418–1423.

26.

, Lin

, Zhang

, et al. Optimal frequency of shock wave lithotripsy in urolithiasis treatment: A systematic review and meta-analysis of randomized controlled trials. J Urol, 2013; 190:1260–1267.

27.

Semins

, Trock

, Matlaga

. The effect of shock wave rate on the outcome of shock wave lithotripsy: A meta-analysis. J Urol, 2008; 179:194–197.

28.

Koo

, Beattie

, Young

. Improved cost-effectiveness and efficiency with a slower shockwave delivery rate. BJU Int, 2010; 105:692–696.

29.

Elkoushy

, Hassan

, Morehouse

, et al. Factors determining stone-free rate in shock wave lithotripsy using standard focus of Storz Modulith SLX-F2 lithotripter. Urology, 2011; 78:759–763.

30.

Ordon

, Andonian

, Blew

, et al. CUA Guideline: Management of ureteral stones. CUAJ, 2015; 9:E837–E851.