Changes in Urolithiasis Referral Patterns for Shock Wave Lithotripsy over a Decade: Was There Adherence to AUA/EAU Guidelines?

Abstract

Objective

The primary objective was to assess changes in referral patterns of urolithiasis for shock wave lithotripsy (SWL) over a decade. The secondary objective was to evaluate the effect of the number of years of practice of referring physicians on these referral patterns.

Methods

A retrospective review of SWL database was performed for consecutive referrals for SWL at a tertiary stone center between December 1999 and December 2013. Patient demographics and stone characteristics were assessed. The stone location at the time of referral was used as the reference. Retreatments were excluded. In addition, years of practice of the referring physicians were calculated. The 2007 AUA/EAU guidelines on urolithiasis were considered as a reference.

Results

A total of 8,992 SWL treatments were included. After December 2007, there was a significant increase in the percentage of renal pelvic stones referred for SWL (23.0 vs. 27.1%, p < 0.001). Conversely, proximal ureteral stones significantly decreased after 2007 (24 vs. 18.2%, p < 0.001) including stones > 10 mm (5.1 vs. 2.9%, p < 0.001). Otherwise, there were no changes in the referral patterns for SWL of other stone locations before and after December 2007 (p > 0.05). Furthermore, percentage of stones referred for SWL by urologists practicing for less than 10 years significantly decreased after December 2007 (29.5 vs. 22.8%, p < 0.001).

Conclusions

The significant reduction in the referral of proximal ureteral stones after December 2007 corresponds to the latest AUA/EAU guidelines on management of ureteral stones.

Introduction

Since installation of Human Model 2 electrohydraulic lithotripter in Munich in 1982 [1], shock wave lithotripsy (SWL) has emerged and established itself as a first-line option for management of urolithiasis. However, stone-free rates (SFRs) post-SWL depends on stone-related factors such as size, location and Hounsfield units [2,3,4]. In addition, SWL outcomes also depend on patient-related factors such as skin-to-stone distance and renal anomalies [5,6], operator-related factors such as urologists and radiological technologists [4,7,8], and the type of lithotripter used [9].

The latest American Urological Association/European Association of Urology (AUA/EAU) guidelines published in December 2007 recommended that either SWL or ureteroscopy are acceptable first-line treatment options for treatment of proximal ureteral stones due to comparable overall SFRs (82 and 81%, respectively) [10,11]. However, a higher SFR was noted for proximal ureteral stones > 10 mm managed by ureteroscopy rather than SWL (79 vs. 68%). Therefore, these guidelines recommended ureteroscopy as an alternative first-line option for management of patients with proximal ureteral stones.

Previous studies on SWL referral patterns have revealed mixed results. The study of Grampsas et al. [12] showed that there were no significant changes in the referral patterns from 1987 till 1996. However, this group did not include mid and distal ureteral locations. On the other hand, Lorber et al. [13] showed that referrals for proximal and distal ureteral stones significantly increased while referrals for renal pelvic and staghorn stones significantly decreased. However, the study period was only till August 2007. Therefore, there have not been any studies examining tertiary stone centre referral patterns before and after the publication of the latest AUA/EAU guidelines. Therefore, the aim of the present study was to assess changes in the location of stones managed by SWL at a single tertiary center over the period from December 1999 to December 2013 and evaluate whether there was adherence to the AUA/EAU guidelines. The second aim was to evaluate the effect of the number of years of practice of referring physicians on these referral patterns. We hypothesize that there were changes in the referral patterns of ureteral stones after the publication of the AUA/EAU guidelines. In addition, we hypothesize that the younger urologists would refer fewer patients for SWL.

Patient and Methods

A retrospective review of prospectively collected SWL database was performed for consecutive patients referred for SWL at a tertiary stone center between December 1999 and December 2013. Patients' electronic database contained data regarding patient age, sex, location, size, and laterality. These data were recorded upon presentation to the stone centre. SWL has been conducted in our institution since 1984 using Siemens Lithostar (Siemens Medical Solutions, Erlangen Germany) till August 2004, Philips Litho Diagnost M (Philips Healthcare, Eindhoven, Netherland) till June 2009, and Storz Modulith SLX-F2 (Storz Medical, Kreuzlingen, Switzerland) till present. The first 2 lithotripters had electrohydraulic generators while the last one is an electromagnetic lithotripter with dual focal zones.

The location of the original stone referred for SWL was used to evaluate the referral pattern. Therefore, patients referred for retreatment of the same stone or its fragments were excluded. Stone location was recorded in the database by the urologist performing SWL and the referring urologist was identified from the database. The AUA/EAU guidelines were released in December 2007. Therefore, this date was considered as a cutoff to compare the changes in referral patterns before and after December 2007. Stone locations were categorized into upper and middle calices, lower calices, renal pelvis, proximal ureter, mid-ureter, and lower ureter. Furthermore, referring physicians and their years of practice were assessed to see whether there was an effect of the number of years of practice on the referral patterns and guidelines adherence.

Statistical Analysis

Data analysis was done using the commercially available Statistical Package of Social Sciences for windows (SPSS, Chicago, IL), version 20. Descriptive data were presented in terms of means and 95% confidence interval (CI) of the mean. Continuous variables were compared using Student t-test while Fisher's exact test was used to compare categorical variables with two-tailed p < 0.05 considered as statistically significant. Pearson's correlation analysis was used to detect changes in stone location over time. A multivariate general linear model was used to detect the possible confounders.

Results

A total of 8,992 SWL treatments were analyzed, including 4,954 (55.1%) on the left side with a mean overall stone size of 9.6 ± 3.9 mm. The mean stone size in terms of stone locations were 9.1 ± 3.6, 9.6 ± 3.9, 12.2 ± 4.8, 8.9 ± 3.1, 8.7 ± 2.9, and 7.7 ± 2.4 mm for the upper and middle calices, lower calyx, renal pelvis, proximal ureter, mid-ureter, and lower ureter, respectively. The overall proportions of patients treated for stones ≤ 10 mm significantly increased over time (r = 0.79). However, the proportion of patients managed for proximal ureteral stones significantly decreased after December 2007 (r = −0.64) with concomitant progressive increase in pelvic stones (r = 0.72).

A total of 5,322 (59.2%) were included from December 1999 till December 2007 and 3,670 (40.8%) from January 2008 till December 2013 (table 1). There was no significant difference between both groups in terms of left-sided stones (55.3 vs. 53.2%, p = 0.13) or overall mean stone size (95% CI) [9.3 (8.4–9.7) vs. 9.7 (9.5–9.8) mm, p = 0.72], respectively.

Table 1.

Distribution of patients referred for SWL stratified by stone locations before and after December 2007

Stone location	Dec. 1999–Dec. 2007 No. (%)	Jan. 2008–Dec. 2013 No. (%)	p
Upper and mid calices	658 (12.4%)	492 (13.4%)	0.22
Lower calyx	1061 (19.9%)	690 (18.8%)	0.29
Renal pelvis	1225 (23.0%)	995 (27.1%)	< 0.001
Proximal ureter	1277 (24%)	668 (18.2%)	< 0.001
Mid ureter	329 (6.2%)	260 (7.1%)	0.21
Distal ureter	772 (14.5%)	565 (15.4%)	0.42
Total	5322 (59.2%)	3670 (40.8%)	NA

In terms of stone location, the proximal ureter was the most common location for SWL referral prior to December 2007, whereas renal pelvis was the most common location for SWL referral after January 2008 (table 1). After December 2007, the percentage of renal pelvic stones referred for SWL significantly increased (23.0 vs. 27.1%, p < 0.001). On the other hand, proximal ureteral stones referred for SWL significantly decreased after December 2007 (24.0 vs. 18.2%, p < 0.001) including not only stones > 10 mm (5.1 vs. 2.9%, p = 0 < 0.001) but also stones ≤ 10 mm (18.9 vs. 15.3%, p < 0.001) (table 1, fig. 1 and 2). Otherwise, there were no changes in the referral patterns for SWL of other stone locations in terms of the upper and middle calyceal stones (p = 0.22), lower calyceal stones (p = 0.29), middle ureteral stones (p = 0.21), and lower ureteral stones (p = 0.42) before and after December 2007, respectively (table 1).

Fig. 1.

Changes in urolithiasis referral patterns for SWL.

Fig. 2.

Percentage of proximal ureteral stones referred for SWL before and after December 2007 stratified by stone size.

The referring urologists' years of practice were available for 8,603 (96%) of all SWL procedures, including 4,949 (93%) before December 2007 and 3,591 (98%) after December 2007. Of interest, the percentage of stones referred for SWL by physicians in practice for less than 10 years significantly decreased after December 2007 (29.5 vs. 22.8%, p < 0.001) (fig. 3).

Fig. 3.

Changes in urolithiasis referral patterns before and after December 2007, stratified by the number of referring physicians' years of practice.

Discussion

Clinical guidelines were defined as “systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances” [14]. Their importance is greatly appreciated especially with increasing volume of published medical research. Therefore, no one can deny the impact of clinical guidelines on improving decision making and the outcome of health care by providing the latest and best evidence-based medical care regarding the best treatment options for a given disease. However, clinical practice guidelines may not be followed since selection of one modality versus another depends not only on stone- and patient-related factors but also availability and training of urologists in addition to preferences of patients and urologists [15,16,17].

In the case of urolithiasis, both AUA and EAU have agreed on a consensus guideline in December 2007. Whereas in the 1997 AUA guidelines [18], SWL was the only first-line treatment option for proximal ureteral stones, the revised 2007 AUA/EAU guidelines recommended either SWL or ureteroscopy as a first-line treatment option. The present study assessed the changes in location of stones referred for SWL and whether these changes reflect changes in the AUA/EAU guidelines. The proximal ureteral stones were the most common location being treated with SWL prior to December 2007. However, after December 2007, proximal ureteral stones referred for SWL significantly decreased (24 vs. 18.2%, p < 0.001) (fig. 1). Interestingly, both ≤ 10 mm and > 10 mm proximal ureteral stones significantly decreased after December 2007 (18.9 vs. 15.3%, p < 0.001) and (5.1 vs. 2.9%, p < 0.001), respectively. There are possible explanations for this. First, ureteroscopy is being performed especially for stones > 10 mm. Another explanation is the treatment of patients with medical expulsive therapy as suggested by the same guidelines for patients presenting with stones < 5 mm without any signs of renal impairment or pyelonephritis. These results may suggest adherence of the local urologists with the revised 2007 AUA/EAU guidelines. Previously, clinical guidelines have been shown to change practice patterns dramatically [19]. Several meta-analyses have evaluated the effect of clinical guidelines on the medical practice patterns and have shown that use of guidelines was associated with a moderate positive impact on patient care and outcomes. However, the size of improvements in performance might be varied considerably [20].

In the current study, there was significant increase in the percentage of renal pelvic stones referred for SWL after December 2007 (23.0 vs. 27.1%, p < 0.001). This finding does not contradict the recommendations of clinical guidelines for management of urolithiasis. Excellent SFR could be achieved by SWL for all intra-renal stones < 20 mm except for the lower pole stones [21,22]. Therefore, the EAU guidelines for urolithiasis recommended SWL as the first-line management for these renal pelvic stones [21].

Given the current guidelines, referral patterns also depend on the level of training of the urologist in performing alternative procedures such as ureteroscopy and the availability of different resources such as flexible fiberoptic ureteroscopes and holmium laser lithotripter. In this study, percentage of stones referred by urologists practicing for less than 10 years significantly decreased (29.5% versus 22.8%; p < 0.001). This could be explained by the preference of young urologists for endoscopic procedures over SWL. Scales et al. [23] found that urologists who recently completed residency training used ureteroscopy more often in management of urolithiasis (Odds ratio: 1.05 per year, 95% CI: 1.01–1.09, p = 0.02). Furthermore, they emphasised the preferences of both patients and urologists in choosing one modality versus another. Likewise, a recent analysis of board certification and recertification logs by Matlaga et al. [16] showed that more recently trained urologists were more likely to use ureteroscopy than SWL, where 52% of candidates for initial certification used ureteroscopy whereas SWL was used by the majority of first and second re-certification candidates (57.4 and 60.5%, respectively). Similarly, a recent population-based study over the last 2 decades detected a significant increase in ureteroscopy utilization (24.6–59.5%, p = 0.0002) and a significant decrease in SWL (68.5–33.7%, p < 0.0001). By the end of 2004, ureteroscopy had become the most widely used procedure [24].

There are several limitations of the present study. Besides being a retrospective study, stone locations were not independently confirmed. Furthermore, it is not known whether percutaneous nephrolithotomy, ureteroscopy or medical expulsive therapy was offered to patients not treated with SWL. This is because our centre is a tertiary referral centre where most community urologists refer patients to undergo SWL. However, the present study is the first of its kind in terms of evaluating guidelines adherence in the referral patterns of about 9,000 stones being treated with a tertiary stone center over more than a decade.

Conclusion

The significant reduction in the referral of proximal ureteral stones after December 2007 corresponds to the latest AUA/EAU guidelines on management of ureteral stones. Furthermore, referrals from physicians with less than 10 years of practice significantly decreased after December 2007.