Dear Sir,

We read the article by Sener et al. [1] with great interest. We believe that their prospective randomized study which they compared flexible ureterorenoscopy (F-URS) to shock wave lithotripsy in the management of lower pole stones <1 cm in diameter will make precious contribution to the literature for the enlightment of this issue. The authors designed the study so as to discuss success rates, potential complications, invasiveness, requirement for anaesthesia, and hospitalization. They found F-URS superior over ESWL in the treatment of lower pole stones <1 cm in diameter with comparable complication, and higher success rates, and lesser number of treatment sessions.

These treatment modalities attract much attention owing to their higher success rates, minimally invasive characteristics, and lower complication rates in the management of small lower pole stones. However as is known, challenging lower pole anatomy can be quite adversely influential, and restrictive in the success of these treatment modalities. In the present study, as indicated by the authors among the limitations of the study, they did not assess anatomical measurement such as infundibular width (IW), and length (IL), lower pole infundibulopelvic angle (IPA), and pelvicalyceal height (PCH).

As far as we know, the effective role of renal pelvicalyceal anatomy on the success of SWL in the treatment of lower pole stones has been revealed in various studies. İn this context, recently, Resorlu et al. [2] have reported the effective role of pelvicalyceal anatomy in the success of retrograde intrarenal surgery (RIRS) performed for the treatment of lower pole stones. They reported that stone size and IPA were the most important factors effecting stone-free state after RIRS, however IW, IL and PCH had no influence on elimination of stone fragments following F-URS.

Finally, we think that if abovementioned factors which is proven influence the success rates were analyzed in this investigation, this well-designed prospective randomized trial would make even greater contributions to the literature.