STONE DISEASE

The Learning Curve in the Training of Percutaneous Nephrolithotomy
Tanriverdi O, Boylu U, Kendirci M, Kadihasanoglu M, Horasanli K, Miroglu C
2nd Urology Department, Sisli Etfal Training and Research Hospital, Istanbul, Turkey
Eur Urol. 2007; 52: 206-11

• Objectives: To investigate the learning curve in the training of percutaneous nephrolithotomy (PCNL).
• Methods: A total of 104 PCNL cases were included in this evaluation to define the learning curve of a surgeon with no previous experience at performing solo PCNL. Two parameters of expertise were reviewed, namely the operation and fluoroscopic screening times. The operation time was calculated as the beginning of access with the needle until the nephrostomy tube was placed and secured. PCNL procedures were analyzed in seven sets of 15 cases regarding the operation and fluoroscopy times, stone size, stone clearance rate, blood transfusion rate, and estimated blood loss.
• Results: The mean operation time was 2.4 h for the first 15 patients. It decreased to a mean of 1.5 h for cases 46 through 60. No further decrease in the operation time was observed after case 60. The fluoroscopic screening time was a peak of 17.5 min in the first 15 cases, whereas it dropped to a mean of 8.9 min for cases 46 through 60. The decline in the mean fluoroscopy screening time continued in cases 61 to 104, but the decline was not significant. There was no significant difference in stone size, stone clearance rate, blood transfusion rate, and estimated blood loss among each set of cases.
• Conclusions: This study suggests that the surgical competence in PCNL can be reached after 60 cases. PCNL and fluoroscopy times drop to a steady-state level after performing 60 procedures.
  
  
• Editorial Comment
  It is important first to note that this study reflects the learning curve for only one surgeon, and one would anticipate a range of learning curves dependent on prior experience with other procedures that require the Seldinger technique and fluoroscopic guidance and certainly innate skills might play a role. If safety is the primary outcome, then the transfusion rate suggests that after 15 cases, competency is achieved. If efficiency is the primary outcome, then the fluoroscopic time and operative time suggests that after 60 cases, competency is achieved. However, if stone-free results are the bar to judge competency, it appears that more experience is needed. The authors report only a 75% stone-free rate, though a liberal definition of 3 mm residual fragments or less was utilized. In addition, one should note that though 17% of patients had staghorn calculi and more had upper calyceal stones, only 4% of patients had an upper calyceal puncture. Defining the learning curve for an intercostal puncture may require another study!

Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA
E-mail: endourol@yahoo.com