It is fully recognized that ureteroscopy (URS) is gaining popularity among the urologist community. The trend towards this technology is now perceived in most of the countries and for almost all ureteral and renal stone sizes. As the literature evidence level is still limited, the European guidelines continue to recommend shockwave lithotripsy (SWL) or “endourology” modalities for a kidney stone smaller than 2 cm, and SWL or URS for a ureteral stone [1]. Even with this popularity towards the usage of URS, greater evidence and information are needed. The Clinical Research Office of the Endourological Society (CROES) Study group has started to produce interesting and pertinent evidence due to their large prospective database collected in collaboration with 114 centers in 32 countries. It illustrated very well the interest by every endourologist to better describe this minimally invasive procedure. Their findings are helping physicians to understand what is done in the real-world practice for patients with ureteral and kidney stones.

Jean de la Rosette published on behalf of the CROES URS Study group the entirely collected data of 11,885 patients [2]. They showed a low rate of pre-stented patients (19.7% of patients). It is exactly in accordance with the recommendation of the EAU guidelines that do not recommend to pre-stent the patient before a URS [1]. Moreover, what would probably be examined in a near future is the treatment of stone by URS for patients with renal abnormalities and solitary kidney. It is another advantage of this large cohort of patients that provide several renal abnormalities that are rarely observed in real life. It is difficult to publish a study with adequate number of patients with these abnormalities other than doing a multicentric collaboration. Also, they presented a broad range of all the complications following URS including a rate of 0.04% of death. It is raising the concern that URS is maybe considered a minimally invasive and safety procedure with an overall complication rate of 4%, but we should not banalize this technique. We still need to improve data involving the safety and efficiency of this procedure with higher volume cohort to illustrate better the major risks of URS if done with inadvertence.

Likewise, Dr. Kandasami published the first large prospective study of the impact of case volume on outcomes of URS for ureteral stones [3]. The median case volume was 67, and it was decided to be the margin between the low- and high-volume centers. The main findings were patients treated in high-volume center had shorter operative time (39.6 vs 48.3 min, p < 0.001), shorter postoperative length of stay (1.8 vs 2.3 days, <0.001), higher stone-free rate (SFR) (91.9 vs 86.3, <0.001), lesser intraoperative complications (94.8 vs 91.1%, <0.001), lesser total postoperative complications (2.2 vs 3.6%, <0.001) and major complications (0.3 vs 0.8%, <0.003), lesser retreatment rate (7.1 vs 10%, <0.001) and readmission within 3 months (6.4 vs 11.8%, <0.001). It is relatively new and attractive message that reiterated the importance of the technicality beyond this procedure.

The best treatment of renal stones is still now unclear considering the stone-free rate and complications rate following the procedure. Percutaneous nephrolithotomy is currently considered the most efficient in term of SFR, but with a higher rate of complication that could also variate depending on the localization of the stone. The CROES URS study group recently reported the outcomes of FURS for 1210 patients with solitary kidney stones. It is nothing comparable with the existing publications and it provides worldwide information that FURS is efficient for renal stones [4]. Skolarikos A. reported a success rate of 90% (SFR ≤1mm) for a stone of less than 1cm of any location. In addition, for stones up to 15mm, the SFR remains high at 80%. It reemphasizes the usefulness of FURS even for stone between 1 and 2 cm, an aspect that when we look at the guidelines, there is still a gray area [1]. As expected, the probability of stone-free is decreasing with the increasing stone size. With the data provided in their study, patients should be informed that the retreatment rate is 10.7 and 33.3% for stone between 1–2 cm and larger than 2 cm, respectively. Furthermore, for stone larger than 2 cm, there is a higher risk of urinary tract infection (UTI) (3.7% p = NS), postoperative fever (7.4% p < 0.05) and readmission rate (34%) within 3 months. Then, these patients should remain operated only in high-volume center.

Another finding of interest with their large cohort was the matched case-control analysis on antibiotic prophylaxis to evaluate the post-operative infection rates in patients with a negative urine culture before the procedure [5]. Certainly, these findings will have to be confirmed with a randomized controlled trial to avoid bias, but these data certainly rekindle the debate regarding the present guidelines for antibiotic prophylaxis that are currently based on limited evidence. In their analysis, administration of antibiotic prophylaxis differed widely between countries from 13 to 100%. Moreover, it seems that the prevalence of postoperative UTI or fever remains low and unchanged with the use of antibiotic prophylaxis, either for ureteral or kidney stones. High ASA score (III-IV) and being a female conferred higher post-operative fever and UTI. More specifically, Crohn's disease and cardiovascular disease were also associated with a higher risk of UTI than anticoagulation therapy and higher stone burden more likely to develop fever during the postoperative course. This important question about antibiotic prophylaxis is not yet resolve, and significant costs are also related to this matter of interest.

Endourological Society with the CROES URS study group has showed the real interest and collaboration in the endourologist community all around the world. It gives a new perspective on data concerning URS, and it raises the level of knowledge and understanding for this more than ever exerted procedure. Moreover, providing that kind of large database is greatly promising for many of the expectations by endourologists. We are convinced that we will yet learn in the near future from the CROES URS study group publication, and probably by all other collaborative works by the CROES.