APPLICATION OF ULTRASOUND FOR IMMEDIATE STONE CLEARANCE ASSESSMENT IN LATERAL MINI-PERCUTANEOUS NEPHROLITHOTOMY

Abstract

Objectives: To evaluate the value and accuracy of intraoperative ultrasound (IOUS) for the immediate detection of residual stones compared to postoperative NCCT in patients undergoing lateral mini-PCNL.

Methods: A prospective case series study was conducted on 37 patients at Hue Central Hospital from January 2025 to June 2025. After the surgeon confirmed the stone-free kidney via endoscopy, intraoperative ultrasound was performed for re-evaluation. The results were compared against postoperative NCCT, with clinically significant residual fragments defined as >4 mm.

Results: The mean patient age was 54.8±9.7 years, with an average stone size of 26.35±8.2 mm. The mean operative time was 75.2±15.8 minutes. The final stone-free rate assessed by IOUS was 81.1%, while the final stone-free rate determined by NCCT (residual stones ≤4 mm) was 75.7%. Compared to NCCT, IOUS for detecting residual stones >4 mm demonstrated a sensitivity of 66.7%, specificity of 96.4%, positive predictive value of 85.7%, and negative predictive value of 90.0%. The overall accuracy was 89.2%, with an area under the receiver operating characteristic curve (AUC) of 0.815.

Conclusions: IOUS is an effective, safe, and valuable diagnostic tool for detecting residual stones during mini-PCNL in the lateral decubitus position. This method helps increase stone-free rates and reduce radiation exposure without increasing complications. Despite some limitations with minimal stone fragments, the high negative predictive value empowers surgeons to confidently conclude the procedure.

Keywords: lateral position; ultrasound; assessment of stone clearance; residual stones