Comparative study of retrograde intrarenal surgery and micropercutaneous nephrolithotomy in the treatment of intermediate-sized kidney stones

Objective: Retrograde intrarenal surgery (RIRS) has proven efficacy with minimal morbidity in the treatment of intermediate-sized kidney stones. The aim of this study was to examine the feasibility of micropercutaneous nephrolithotomy (microperc) for this indication and evaluate its results compared with those of RIRS.

Material and methods: From September to December 2013, we performed a comparative prospective study between RIRS and microperc, with 20 consecutive patients with intermediate-sized (1-3cm) kidney stones. We employed a flexible dual-channel ureteroscope (Cobra, Richard Wolf GmbH) and a Microperc 4.85/8 Fr (with the patient supine) with flexible fiberoptics (0.9mm, 120° and 10,000 pixels) (PolyDiagnost GmbH). The study variables were demographic data, stone characteristics, percentage of stone elimination, complications (Clavien-Dindo), surgical time, hospital stay and need for auxiliary procedures.

Results: The patients underwent RIRS (n=12) or microperc (n=8). There were no differences in the demographics or stone characteristics between the 2 groups. The percentage of stone elimination with RIRS and microperc was 91.7% and 87.5% (P=1), respectively. One of the patients who underwent RIRS (8.3%) experienced postoperative fever; one of the patients who underwent microperc (12.5%) experienced postoperative colic pain (both cases were classified as Clavien I). The operative times were similar: 120min (111.2-148.7) and 120 (88.7-167.5) min for RIRS and microperc (P=.8), respectively. None of the patients required a blood transfusion. The hospital stays were also equivalent: 1 day (1-2) and 1.5 days (1-3.5) for RIRS and microperc (P=.33), respectively. Two patients treated with microperc (25%) required auxiliary procedures (simultaneous RIRS and flexible nephroscopy after percutaneous trajectory dilation to treat, in both cases, a significant fragment that had migrated to an inaccessible calyx), and 1 patient in the RIRS group (8.3%) required percutaneous nephrolithotomy due to unfavorable infundibular-calyceal anatomy (P=.54).

Conclusions: Microperc is a minimally invasive method that is emerging as an effective and safe treatment for intermediate-sized kidney stones. Studies are needed to better evaluate its cost-effectiveness, the need for complementary treatments and its possible complementarity with RIRS when working with patients in the supine position.