PCNL Without Reverse Catheterization in the Split-leg Prone Position: A Randomized Controlled Trial.

### 1. Research Background Percutaneous nephrolithotomy (PCNL) is currently the first-line treatment for upper urinary tract stones larger than 2 cm. It is minimally invasive and enables rapid recovery, so it has gained patients' approval. When performing PCNL, most urologists first place a ureteral catheter retrogradely into the ureter on the affected side with the patient in the lithotomy position, and then change the patient to the prone position for percutaneous renal puncture and stone extraction. The retrogradely inserted catheter can be used for injecting water or contrast agents in reverse, which facilitates percutaneous renal puncture and also prevents stone fragments from entering the ureter during the lithotripsy process. However, when performing PCNL in the standard prone position, it may sometimes be difficult to place an anterograde internal stent or treat ureteral stones, requiring the patient to be changed back to the lithotomy position again. This entails another round of disinfection and draping, thus increasing the workload of the medical team and prolonging the operation time.

In recent years, with urologists gaining more experience in percutaneous renal puncture and the improvement of the quality of ultrasound images, the application of ultrasound-guided percutaneous renal puncture and fistulization has become increasingly popular, being no less effective than X-ray. Ultrasound-guided percutaneous renal puncture and fistulization does not rely on retrograde pyelography. Even experienced urologists do not need to perform retrograde intubation and water injection to form an "artificial hydronephrosis", which saves the operation time required for the traditional procedure of retrograde intubation in the lithotomy position followed by changing to the prone position, and also avoids the risk of infection caused by the possible increase in renal pelvic pressure during retrograde water injection. However, not placing a retrograde catheter may lead to difficulties in puncturing a non-hydronephrotic kidney. During the PCNL lithotripsy process, if stone fragments enter the ureter and are difficult to manage anterogradely, retrograde ureteroscopic treatment is required again, which is difficult to perform in the traditional simple prone position and requires changing back to the lithotomy position. In fact, retrograde ureteroscopic operations can be carried out in the split-leg prone position, which can meet various requirements for anterograde and retrograde operations during PCNL in a single position. This is the particular advantage of PCNL in the split-leg prone position.

Direct percutaneous renal puncture and stone extraction under ultrasound guidance without retrograde intubation in the split-leg prone position can save the operation time of the traditional procedure of intubation in the lithotomy position followed by changing to the prone position. However, there is a risk of stone fragments entering the ureter during lithotripsy. This can be addressed by retrograde ureteroscopy in the split-leg prone position. In addition, higher technical requirements are imposed on ultrasound-guided percutaneous renal puncture. Whether this technique is feasible still needs to be clinically verified.

• 2. Research Objectives To conduct a single-center, prospective, randomized, controlled study to explore the safety, feasibility, and potential advantages of percutaneous nephrolithotomy without retrograde intubation in the split-leg prone position.

• **Primary outcome measures**: The time to establish the first tract, operation time.

• **Secondary outcome measures**: Stone-free rate, surgical complications.

• 3. Research Design