Urolithiasis is a common condition in urology, influenced by environmental and genetic factors. Its prevalence ranges from 7-13% in North America, 5-9% in Europe, and 1-5% in Asia. In Taiwan, the age-adjusted rate for upper urinary tract urolithiasis medical visits was 1,278 per 100,000 in 2010. Renal stones, particularly staghorn stones, require aggressive treatment to prevent infection and renal function loss. How to treat the staghorn stone remains a challenging problem for the practicing urologist. Currently, PCNL is the standard of treating large renal stones, including staghorn stones. With the device's innovation and advance, small calibers of the tract creation have minimal invasive technique, offering the same stone-free rate and fewer comorbidity results. But the minimally invasive procedure treating the large staghorn stone has more difficulty and less stone-free rate. This study evaluates the efficacy and outcomes of single middle access tract miniPCNL in treating complete staghorn stones and identifies factors affecting the stone-free rate (SFR).

A retrospective analysis was conducted on patients undergoing miniPCNL for complete staghorn stones. Data included patient demographics, stone characteristics, perioperative parameters, complications, and postoperative SFR, assessed via imaging. Multivariate analysis was used to determine factors influencing SFR.

The mean operative time for complete staghorn stones was approximately 2 hours. The average postoperative hospital stay was 3 days. The overall SFR was 16.3%. Residual stones were analyzed using postoperative KUB imaging. Residual stones in all three calyces is 16.7% (n=5). Most residual stones (83.4%) were found in one or two calyces. Operation outcome and complications was analyzed. Hemoglobin drop averaged is <0.7 g/dL postoperatively. Three patients required RBC transfusion. Two patients developed fever due to urinary tract infection, and one patient experienced sepsis. No pleural injuries occurred due to the middle calyceal access approach. Overall complication rate is 16.2%. No patient was mortality. Residual stones were evenly distributed among the upper (17 cases), middle (20 cases), and lower (17 cases) calyces. Residual stone size was <1 cm in the majority of cases.

The study demonstrates that single middle access tract miniPCNL is an effective and minimally invasive approach for complete staghorn stone. It's a viable option for complete staghorn stones, achieving a high SFR with manageable complications. Patient selection based on stone characteristics and renal anatomy is crucial for maximizing success rates. Residual stones are primarily distributed among one or two calyces, suggesting the need for adjunctive procedures to improve outcomes. Further studies comparing different access techniques may provide deeper insights into optimizing success rates.