To investigate the safety, practicability and effectiveness of CT and B-ultrasound pre-positioning "three-step" percutaneous nephrolithotomy (PCNL) for the treatment of upper urinary tract calculi.

From March 2018 to March 2022, the data of 210 renal calculi and 138 upper ureteral calculi diagnosed in Loudi Central Hospital were retrospectively analyzed. Among them, 164 sides of the study group were operated with "three-step" PCNL with prone position CT and B ultrasonic pre-positioning. In the control group, 184 sides were operated with traditional PCNL in prone position only by manual black and white ultrasound (convex array probe 3.5 MHz) guiding the position.

Two patients in the study group experienced postoperative fever and improved after conservative treatment. In the control group, 6 cases experienced postoperative fever, 1 case established a channel through the spleen, and 11 cases established a channel through the pleura, all of which improved after conservative treatment. There were 26 cases of postoperative bleeding, of which 23 cases improved after conservative treatment such as clamping renal fistulas, 2 cases of massive bleeding were treated with superselective embolization, and 1 case was changed to open nephrectomy for hemostasis. The puncture time for the two groups of surgeries was 3 (3.0, 5.0) min and 8 (7.5, 10.0) min, respectively. The success rates of one-time puncture were 98.2% and 82.1%, and the primary stone clearance rates were 97% and 71.7%, respectively. There were significant differences in puncture time, one-time puncture success rate, primary stone clearance rate, and postoperative complications indicators (P<0.05).

The "three-step" PCNL with CT and B-ultrasound pre-positioning is safer, more practical and more effective than the traditional PCNL in the treatment of upper urinary tract calculi, which can reduce the learning curve, improve the stone clearance rate and reduce the incidence of complications.