Dear Editor,

We thank you for this opportunity to publishing our article as well as this response letter. In the article, we compared patients treated by flexible ureterorenoscopy (F-URS) against shock wave lithotripsy (SWL), in lower pole stones smaller than 1 cm. In the article, we excluded the patients with steep (<30°) infundibulopelvic angles (IPA) [1]. Recently, we were made aware of a letter, proposing including the patients we excluded.

We thank the authors for proposing the article, but we believe it would be best to exclude the patients with steep IPA. In European Association of Urology guidelines on Urolithiasis, it is proposed that worse success rates are accomplished when IPA is <30° [2]. Even though SWL is still recommended for lower pole stones, we believe patients with steep infundibulopelvic angles would add considerable bias to the study against SWL.

If the goal is to investigate the lower pole anatomy on success and complication rates especially for SWL, the study design should be constructed differently. As there are abundant samples in the literature, we did not plan to clear the path to treat lower pole stones with complex lower pole anatomy, but we look forward to reading the article by the authors.