Evaluating the learning curve of total ultrasound guided percutaneous nephrolithotomy in complex renal stones...

To investigate the learning curve of in the training of total ultrasound(US) guided percutaneous nephrolithotomy(PCNL) in complex renal stones using "30-degree principle" technique.

A total of 80 patients were included in this study to evaluate the learning curve of US guided PCNL in an inexperienced novice. They were divided into 8 groups based on timing of the surgery to evaluate the outcomes within the groups. The operator has mastered the"30-degree triangulation" technique for US-guided percutaneous renal puncture by education and theoretical study. Two important parameters were reviewed, namely US screening time and puncture time. Other peri-operative data were also recorded.

The mean US screening time was 509.3 s for the first 10 cases. It decreased significantly to an average of 226.3 s through 30 to 40. Although the US screening time gradually shortened with accumulated experience and stabilized at an average of 152.5 s through 70-80 cases, there was no significant difference between the following groups. Puncture time declined from 558.8 s in the first group to a mean of 202.3 s in the patients 30 to 40. Consistent with the trend in US screening time, although puncture time continued to decrease, there was no significant difference between them in subsequent patient groups. There were no significant differences in the hemoglobin drop, stone-free rate(SFR), post-hospitalization, or severe complication rate between each groups.

The acceptable outcome of PCNL guided by total ultrasound in complex stones could be achieved after 40 cases under the premise of mastering the "30-degree triangulation"technique. The US screening time and puncture time dropped to a relative steady level after 40 times of practice.