, Volume 29, Issue 6, pp 749-753

The learning curve in minimally invasive percutaneous nephrolitholapaxy: a 1-year retrospective evaluation of a novice and an expert

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The aim of this study was to compare a novice surgeon with an expert surgeon independently performing minimally invasive percutaneous neprolitholapaxy (PCNL) excluding the influence of the expert in the learning curve.


Clinical records of 84 patients (novice: n = 35; expert: n = 49) undergoing minimally invasive PCNL between 04/2007 and 04/2008 were retrospectively reviewed for the following parameters: drop in hemoglobin, operative and fluoroscopy time, length of hospital stay, stone-free rate and complication rate. Complications were graded according to the Clavien classification. Statistical analysis was carried out by student’s t test (Chi-square test) with p < 0.05 considered significant.


The novice surgeon experienced longer median operative and fluoroscopy time, lower stone-free rate and higher re-treatment rate (all p < 0.005) but no longer length of hospital stay (p = 0.19) compared to the experienced surgeon. The novice showed a notable improvement in operating time (p = 0.0208). Altogether, 16 complications occurred in 84 minimally invasive PCNL (19.1%) with five patients (6.0%) encountering grade III complications. Four patients (8.2%) treated by the expert surgeon developed complications (all grade I/II) compared to 12 of the patients (34.3%) treated by the novice surgeon (p = 0.0265). All grade III complications occurred in the first 20 patients of the novice surgeon group.


Despite longer operating time and a lower initial stone-free rate, the novice showed a significant improvement with growing experience and a low rate of higher grade (≥IIIa) complications. This demonstrates that the concept of minimally invasive PCNL can also be learned by urologists who do not have the support of an experienced colleague without endangering patient safety.

D. Schilling and G. Gakis contributed equally to this article.