Abstract: Objective： Contrast enhanced ultrasound (CEUS) is an innovative technique that employs microbubble contrast agents to demonstrate parenchymal perfusion. Ultrasound contrast agent was reported to be directly used in human internal lumen to improve the observation capacity of ultrasound. However, CEUS has never been reported to be used in the guidance of percutaneous renal access in percutaneous nephrolithotomy (PCNL). This study aimed to assess the efficacy of CEUS-guided renal access in PCNL. Methods: In this retrospective study, percutaneous renal access was performed under real-time monitoring of CEUS during PCNL in a cohort of 20 patients with renal stones at Peking University First Hospital. Data regarding patients’ demographic and clinical characteristics, therapeutic regimens, and postoperative information were collected from a comprehensive database containing comprehensive medical records of the patients undergoing PCNL. Briefly, the procedure was as follows. With the patient under general anesthesia, renal access was established by the guidance of CEUS. Afterwords, holmium laser, pneumatic or ultrasonic lithotripsy was used by the same urologist. The patient demographics, stone characteristics and procedure details were noted. Finally, appropriate statistical analyses were performed to evaluate the effectiveness and safety of the CEUS-guided percutaneous renal access in PCNL. Results: All the 20 patients underwent PCNL successfully with the help of CEUS guidance for tract creation. The collecting system was successfully accessed in all the patients, and only one patient underwent re-puncture. All the patients approached through a middle-pole percutaneous access. The median puncture time was 3.9 (2.9-4.6) min, and the median operating time was 112 (98.5-134.5) min. The preliminary stone-free rate of PCNL was 95.0% (19/20) as shown by the kidney, ureter, and bladder (KUB) radiographs 48 h postoperation, and the median decline in hemoglobin level was 10 (5.5-14.5) g/L. Two patients had transient postoperative fever and responded well to antibiotics. In addition, no other major complications were observed. Conclusion: CEUS is a safe and effective alternative way of guidance for percutaneous renal access for PCNL beginners. It makes this procedure more visualized and simpler, and produces clearer images than common ultrasonic ones. PCNL beginners might benefit from this method to shorten the learning curve of PCNL, while it warrants further comparative studies to clarify.

Key words: Percutaneous nephrolithotomy, Percutaneous renal access, Renal stone, Contrast-enhanced ultrasound