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World J Urol. 2011 Dec;29(6):749-53. doi: 10.1007/s00345-010-0553-3. Epub 2010 Apr 18.

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

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  • 1Department of Urology, University Hospital Tuebingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany.



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.

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