Exploration of the Feasibility of Mini-Percutaneous Nephrolithotomy with Gravity-Assisted Low-Pressure Irrigation in the Treatment of Renal Stones with “Cat’s Paw Sign” Pyonephrosis Instead of Multiple Percutaneous Drainage

Introduction: To investigate the feasibility of mini-percutaneous nephrolithotomy (mPCNL) with gravity-assisted low-pressure irrigation in managing renal pelvic stones complicated by multiple calyceal pyonephrosis (characterized by the “cat’s paw sign” on CT scan) as an alternative to multiple percutaneous drainage. Methods: A retrospective analysis was conducted on 7 patients (4 males, 3 females; mean age 52.1 years) who underwent one-stage mPCNL between 2019 and 2023. Meticulous preoperative antibiotic prophylaxis was administered, and intraoperative perfusion pressure was maintained below 100 cm H₂O using gravity irrigation. Results: All operations were completed successfully without major complications (Clavien-Dindo grade >2). Two patients experienced transient fever, which resolved with targeted treatment. Key outcomes included stable preoperative hemoglobin levels (mean: 107.86 g/L) and manageable postoperative inflammatory markers (CRP: 35.54 mg/L at 12 h postoperatively). Conclusions: mPCNL combined with gravity-assisted low-pressure irrigation is a practical alternative for resource-limited centers, enabling single-tract decompression of all obstructed calyces, immediate stone clearance, and acceptable complications. It is particularly suited for small renal pelves with obstructing stones, providing prompt relief of obstruction and infection while minimizing renal parenchymal damage. However, as a pilot study, the small sample size warrants further multicenter studies for validation.