Only Size Matters in Stone Patients: Computed Tomography Controlled Stone-Free Rates after Mini-Percutaneous Nephrolithotomy

Abstract

Objective: To examine and predicting stone-free rates (SFRs) after minimally invasive-percutaneous nephrolithotomy (mini-PNL) based on computed tomography (CT), instead of X-ray or ultrasound control. Patients and Methods: We identified 146 mini-PNL patients with pre- and postoperative CT scans. Patient and stone characteristics were assessed. Stone-free status was defined as ≤3 mm residual fragment after mini-PNL according to postsurgery CT scan. Multivariable logistic regression analyses predicted stone-free status after mini-PNL. Results: Overall, 62 (42.5%) patients achieved stone-free status after mini-PNL. In multivariable analyses, stone size was the only independent predictor for stone-free status (OR 0.9; p = 0.02). Patients with stones > 20 mm were less likely to achieve stone-free status, than those harboring stones 10–20 mm (OR 0.3; p = 0.009). SFRs according to stone size categories (< 10, 10–20, and > 20 mm) were 33.3, 50.5, and 25%. Body mass index (BMI) and stone density (Houndsfield units) were no independent predictors for stone-free status after mini-PNL. Conclusions: We report lower SFRs than expected. Stone size was the only independent predictor for stone-free status after mini-PNL. Patients with larger stones need to be informed about high risk of additional interventions. High BMI and high stone density do not represent a barrier for stone-free status after mini-PNL.