Ultra-mini flexible percutaneous nephrolithotomy in the treatment of moderate-size kidney stones: a new instrument, a preliminary prospective study.

Ultra-mini PNL is increasingly preferred in the treatment of kidney stones. Unlike routine applications of the ultra-mini PNL technique, we aimed to perform kidney stones treatment with an epiduroscopic device that can pass through 11-13-Fr ureteral access sheaths with a flexible structure and which is routine in neurosurgical practice. The study was planned prospectively. The study included 52 patients with mid-sized kidney stones who had presented to our clinic between July 2017 and January 2019. The ultra-mini percutaneous nephrolithotomy was carried out with epiduroscopy routinely used in neurosurgery practice, which can pass through 11-13-Fr ureteral access and has a flexible structure. The perioperative and postoperative parameters were analyzed. The mean operation time was 45.6 ± 4.8 min and entry was provided through a single entry (from the calyx appropriate to the lower pole) in all patients; a second entry tract was not required. No DJ catheter or nephrostomy tube was installed in any patient and the procedures were completed totally without a tube. The mean reduction in hemoglobin values was determined as 0.33 (0.1-1.1) g/dL. None of the patients needed transfusion and no patient developed acute kidney injury. Clinically significant (≥ 3 mm) residual stone was observed in 2 (4%) of the 52 patients, while clinically insignificant (≤ 3 mm) stones were observed in 50 patients (96%). The mean length of hospital stay was 2.5 ± 0.9 days. Ultra-mini flexible percutaneous nephrolithotomy is an effective and safe method in the treatment of medium-sized kidney stones.