Defining the learning curve for percutaneous nephrolithotomy

To define the learning curve for percutaneous nephrolithotomy (PCNL) using three potential surrogate markers of surgical expertise. The learning curve of an endourologist with no previous experience at performing solo PCNL was studied. Three putative parameters of expertise were reviewed, namely, operating time, fluoroscopic screening time, and radiation dose. Operations were analyzed in cohorts of 15 to determine when a plateau was reached for all three variables. Comparison was then made with the results of a surgeon who had performed more than 1600 PCNLs. Stone type and stone clearance rate were also noted. The mean operating time of the novice surgeon fell to a plateau of 92 minutes after 60 cases, but screening time and radiation dose did not plateau until case 115, when values of 231 seconds and 406 cGy/cm2 were recorded, respectively. The senior surgeon had a mean operating time of 98 minutes and screening parameters equivalent to those of the novice surgeon after 115 cases. The complexity of the stones tackled grew with increasing experience, although stone-free rates remained constant. This study of the learning curve of a single surgeon suggests that competence at performing PCNL is reached after 60 cases and excellence after 115. Radiation parameters are a valuable tool in the assessment of operative competence.