Systematic reviews of RCTs are valuable since they inform evidence-based health care decision making and the development of clinical treatment guidelines. Stone disease has many possible treatments, which makes comparative efficacy assessment particularly important. One of the first comparative assessments of ureteral calculi was the 1997 AUA Ureteral Stones Clinical Guidelines Panel summary report.27
At that time the panel stated that the quality of the reviewed literature was so poor that no recommendations could be made without including retrospective clinical case series. The panel ultimately concluded that SWL was first line treatment for stones 1 cm or less in the proximal ureter while stones in the distal ureter could be treated with SWL or URS.
Recognizing the intervening publication of several new RCTs since the guidelines panel summary,27
in 2007 the Cochrane Collaboration4
and the EAU/AUA Nephrolithiasis Guideline Panel28
provided systematic reviews and meta-analyses of ureteral calculus management. The Cochrane Collaboration indicated that URS was associated with a superior SFR but complications and hospitalization were also greater for the URS cohorts.4
However, overall the quality of evidence was poor and further studies were required to better define optimal treatment practices. This review had several design limitations, including the fact that no distinction was made between SWL done with the HM3 lithotripter and other devices. Based on observational data it is a generally accepted tenet that the HM3 is associated with significantly greater treatment success than subsequent lithotripters. Our indirect comparison also showed that the HM3 had results superior to those of other SWL devices for distal stones.
The recent RCT by Zehnder et al comparing the HM3 to the Modulith® SLX-F2 SWL device confirmed that the older HM3 device has better outcomes.29
That study was published too late to be included in our meta-analysis. Also, the Cochrane Review did not account for stone location, which is also a significant predictor URS success.4
In contrast, the EAU/AUA panel analysis was done according to stone site but it also did not account for the different generations of SWL devices used in the source studies, ie SWL-HM3 vs SWL-other.28
The EAU/AUA panel ultimately found that for patients with ureteral stones URS was associated with a greater SFR and this finding was particularly pronounced in the distal ureter. However, the EUA/AUA panel and the Cochrane Collaboration4
recommended that additional RCTs should be done to improve practice guidelines.
In an ideal system robust RCTs would simultaneously compare all interventions of interest. In the realm of stone disease such a trial would incorporate URS, SWL and PNL. However, since such studies are not readily available, indirect comparisons among studies can provide useful evidence. In our analysis the results of multiple RCTs were used to directly and/or indirectly compare treatments to each other in a network meta-analysis. We assessed unambiguous metrics associated with surgical stone treatment, which allowed the most equitable comparisons among treatment modalities, including SFR, retreatment procedures and surgical complications. However, this systematic literature search was limited to the published English language literature. Thus, unpublished conference abstracts, which may not have been published due to publication bias, would have been excluded from analysis.
Our network meta-analysis of patients with distal ureteral calculi showed that URS has advantages over SWL. Immediately after treatment URS was significantly superior to SWL in regard to SFR. However, that difference became smaller with time, which was a consequence of re-treatments. To that end when comparing the SWL and URS cohorts, patients initially treated with URS required fewer re-treatment procedures. In some regards our findings are not surprising or unexpected. The EAU/AUA Panel also reported that URS for distal ureteral calculi was associated with a greater SFR.28
As in the EAU/AUA analysis, in our series source studies were geographically diverse and likely included surgeons with varying skills and technology.
What may be as important as our mentioned findings on distal ureteral calculi is our inability to draw meaningful conclusions when assessing studies of proximal ureteral and renal calculi. Of the literature searched only 4 RCTs were identified for proximal ureteral calculi,19–22
of which 2 were restricted to a stone burden of 1.5 to 2 cm, much larger than the size stone routinely encountered in practice.20,21
The other 2 studies also included patients with renal stones with such great variability in clinical characteristics and outcome metrics that meaningful comparisons were not possible.19,22
Going forward, what is most needed to better elucidate the optimal treatment approaches to proximal ureteral and renal calculi are robustly designed RCTs. However, given the relative scarcity of such studies in the previous decade, it is unlikely that a significant number of these studies will rapidly populate the medical literature in the coming years. In the absence of such studies the next level of appropriate evidence would be well designed observational studies. Our review identified that there is no uniform approach to defining preoperative stone size or location, associated ancillary treatments or even the stone-free outcome. To maximize the benefit of observational studies it is important to develop a commonly accepted terminology that will best permit a comparison of interventions for stone disease.