Micro-percutaneous nephrolithotomy (Microperc) for renal stones, outcomes and learning curve

To report the effectiveness, reliability and learning curve of Microperc, a minimal invasive percutaneous technique using a 4.85-Ch (16-gauge) sheath, in the treatment of nephrolithiasis.

31 consecutive Micropercs for nephrolithiasis<2.5cm were performed by 2 operators in 2 different institutions from the 1st of May 2015 to 31st of December 2017.

The mean size of stones was 19mm±11mm, and mean density was 1048±249UH. Stones were located in lower calyx in 21/31(68%), medium calyx in 3/31(10%), pelvis in 4/31(12%) and were multi-caliceal in 3/31(10%). Five patients (16%) had urinary diversion (4 ileal conduits, 1 enterocystoplasty with Mitrofanoff+bladder neck closure) all of those having neurological disease (2 multiple sclerosis, 3 spinal cord injury). Mean operating time was 83±35min and decreased after short period for both operators. 9/31(29%) patients had complication: 8 (26%) had fever (Clavien II) and 1 (3%) had renal colic pain (Clavien III) (required JJ stent). Stone-free was obtained in 13/31(42%) and 11/31(36%) had residual microfragments<3mm which did not require further treatment, corresponding to a technical success of 78% (24/31). Success rate was similar in patients with urinary diversion and patients with normal anatomy.

This study showed that Microperc was an effective technic for kidney stone treatment with low complication rate, acceptable operating time and short learning curve. Microperc was useful for stones in the lower calyx and/or urinary diversion where retrograde ureteroscopy could reach its limits.

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