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1.5 cm stone in the lower calyx: flexible ureteroscopy versus percutaneous nephrolithotomy: in favor of percutaneous nephrolithotomy.

DOI:10.1097/MOU.0000000000000630 The treatment of lower pole stones (LPS) is the field of great controversy in the literature. Each one of the available treatment options has its own advantages and disadvantages especially for stones 20 mm or less [1]. EAU guidelines propose shock wave lithotripsy (SWL), flexible ureteroscopy (fURS) or percutaneous nephrolithotomy (PNL) for the management of lower calyceal stone, setting in the same time some prerequisites regarding the existence of favorable or not anatomy [1]. It is more than well established in our everyday clinical practice that PNL is the gold standard procedure for large and complex renal stones despite increased complication rates compared with its rivalries (fURS and SWL). No consensus exits though, for the ideal procedure for stones in the ‘gray zone’, such as stones between 1 and 2 cm. Things are getting even more complex because of stone position in the renal calyceal system especially when stones are situated in the lower calyx. The answer to the aforementioned difficult question has been the field of interest for several contemporary studies. In one of them, a randomized control trial, including nearly 600 patients, a trend towards the superiority of PNL compared with fURS was demonstrated in terms of, stone-free rate (SFR) 87.3% for PNL vs. 82.1% for fURS, need for retreatment 4 vs. 9% and need for auxiliary procedures 12 vs. 18% without these results succeeding in reaching statistical significance. Complication rates were slightly increased but not statistically significant for the PNL group compared with fURS [2]. On the same pace, the results of the most recent metaanalysis confirm the superiority of PNL for lower pole stones 2 cm or less, reporting a SFR 91.3% for PNL vs. 68.5% for fURS (risk ratio 1.32 P<0.01 and I1⁄457). Despite the fact that there was no sub-group analysis for stones less than 2 cm and greater than 2 cm, the authors conclude that PNL is the most efficient method for treating stones with size between 1 and 2 cm [3]. Increased invasiveness of PNL compared with fURS led to the development of miniaturized