Clinical study of the puncture success rate during ultrasound-guided percutaneous nephrolithotomy

Objective To evaluate the success rate during ultrasound-guided percutaneous nephrolithotomy (PCNL) and analyze the reasons of puncture failure. Methods A retrospective analysis was performed based on the data of 58 patients who underwent ultrasound-guided PCNL by 4 experienced urologists(10 years' experience of PCNL and more than 80 cases per year)in our center from August 2018 to November 2018. Of all the 58 patients, there were 36 males and 22 females (aged from 22 to 73 years) with the mean age of 51 years. The calculi ranged from 9 mm to 93 mm, with the average of 26.5 mm. The separation of renal collecting system ranged from 5 mm to 30 mm, with the average of 15.1 mm. All of the 58 patients underwent one-stage PCNL and the numbers of punctures, the numbers of percutaneous tubes and the reasons for failure were recorded. Results All percutaneous tubes and surgeries were established and done successfully. Of all the 118 punctures, 74 punctures succeeded by detecting the urine and 68 surgery tracts were established (6 punctures failed because of the dilation). The total puncture success rate was 62.7%(74/118). Of the total 74 successful punctures, 56.8%(42/74)succeeded at the first puncture, 28.4%(21/74)succeeded at the second puncture and 14.9%(11/74)succeeded at least after three punctures. The success puncture rate of the 4 urologists were 59.2%(29/49), 64.1%(25/39), 66.7%(16/24), 66.7%(4/6)respectively, and there were no statistical differences between the puncture success rates of the urologists (P=0.679). Each channel needed 1.7 punctures on average. Fouty-four punctures failed without detecting the urine, including 20 failed punctures because of the puncture tract deviation, 17 punctures without seeing the urine after the core needle being removed, 7 punctures no display on the ultrasound imagine. There were 33 punctures to be tubeless while other 35 indwelling the nephrostomy tubes. Five nephrostomy tubes' position were different with the preoperationally predicted position which means the discrepancy rate was 14.3%(5/35). One patient had complications and classified as Grade II or above on the modified Clavien Grading System of aerothorax. Conclusions The puncture success rate during ultrasound-guided PCNL is not satisfied. The main reasons of puncture failure are the deviation of puncture tract, unclear imaging of puncture tract and other unclear reasons( puncture needle went too deep or superficially or tip of the needle embedded into the stone). Key words: Kidney calculi; Percutaneous nephrolithotomy; Puncture; Success rate