Letter to the editor.

First we'd like to thank V. Malkhasyan and Jan Hrbacek [1, 2] for their kind comments.

We thank Jan Hrbácek for his kind comments regarding our institution, we're all very glad your time here was such a positive experience.

Jan Hrbacek is correct in pointing out some of the major shortcomings of the study such as not being able to achieve randomization despite our original intentions as evidenced by the difference in demographics between the groups. However, the selection of the groups was a compromise between true randomization, and patient treatment ethics.

As with any selection process, including randomization, bias can be introduced if all potential confounding factors aren't taken into account from the outset of the study. All must be done within current standard of care. After consulting with all personnel involved, we agreed on the methodology employed. Our selection process resulted in one we were comfortable for finding answers to our questions while maintaining our standards for clinical care.

While there was a lack of true randomization and the patient groups differed significantly, the difference in results cannot be solely attributed to patient selection as the stone free rates achieved were not necessarily correlated with the severity of the disease as can be evidenced by the less effective results of achieved by patients eligible for ESWL. Our results still permit gaining a good perspective on (or adds to the current body of knowledge regarding) risk, cost, benefit considerations that occur with each modality in clinical practice.

They both raise the issue of lack of comparison with ureteroscopic stone ablation using laser.

Both include the EAU Guidelines for Urolithiasis updated in 2011 in their reference list. The guidelines state that Ho:YAG laser lithotripsy is the preferred method when carrying out (flexible) URS with a grade B recommendation.

V. Malkhasyan makes a point regarding improvements in URS regarding caliber and additional lithotrypsy URS devices such as laser. These improvements in devices and techniques make comparisons of treatment modalities a moving target and, as newer devices and techniques arrive, the subject of further study.

Regarding URS laser ablation, this modality wasn't readily available at our institution during the period of study, which is representative of many institutions at the time.