Prospective Evaluation of Learning Curve of Urology Residents for Percutaneous Nephrolithotomy

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We studied the learning curve for percutaneous nephrolithotomy of urology residents according to stone complexity.


The learning curve of 8 residents with no previous experience of solo percutaneous nephrolithotomy was studied. Stones were classified according to complexity using the Guy stone score. Competence was reviewed using 4 markers, namely operative time, fluoroscopic time, complication rate using the modified Clavien grading system and success rate. Analysis was done in 3-month cohorts to determine how and when competence and excellence were achieved during 1 year of training for various grades of stone. The results of resident surgeons were compared with those of experienced endourologist.


Resident surgeons achieved a plateau in mean operative time and fluoroscopic time for grade I stones after 30 to 35 cases but not for more complex stones. Similarly complications were decreased significantly only in grade I stone cases. Resident surgeons also achieved an almost excellent success rate of 87% for grade I stones only.


This study of the learning curve of residents suggests that competence and near excellence is reached after 30 to 35 cases for grade I stones. However the learning curve for complex stones (grades II to IV) is steeper and requires more experience.

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