The Critical Role of Calyceal Anatomy in Achieving Stone-Free Status After PCNL: A Prospective Study

Introduction: Percutaneous nephrolithotomy (PCNL) is the gold standard for large renal calculi.This study aimed to prospectively evaluate the impact of specific anatomical parameters, measured on retrograde pyelogram, on stone-free rates (SFR) and perioperative outcomes after PCNL. Methods: This prospective, observational study included 350 patients who underwent PCNL. Preoperative anatomical parameters—including calyx diameter, calyx-to-pelvis distance, infundibulopelvic angle (IPA), and maximum calyx-stone angle (max CSA) were measured on retrograde pyelograms. Outcomes assessed were SFR at 4 weeks, complications (Clavien-Dindo), and haemoglobin drop. Statistical analysis included ROC curve, univariate, and multivariate regression analyses. Results: The overall SFR was 91.7%. ROC analysis identified max CSA as the strongest anatomical predictor of SFR (AUC 0.722), with a cut-off of ≥ 72° (sensitivity 69.0%, specificity 74.5%). On multivariate analysis, tract length > 10 cm (p = 0.011) and GUY’S Score Grade 1 (p = 0.018) were independent predictors of SFR. Major complications (Clavien-Dindo ≥ 2) occurred in 7.4% and were independently predicted by stone density ≤ 950 HU (p = 0.001) and intraoperative bleeding (p = 0.006). A significant haemoglobin drop (≥ 1.95 g/dl) was independently associated with nephrostomy tube requirement (p = 0.032), higher hydronephrosis grade (p = 0.042), max CSA ≥ 72° (p = 0.008), and multiple tracts (p = 0.021). Conclusion: Calyceal anatomy, particularly the maximum calyx-stone angle, is a significant predictor of stone-free status after PCNL. Anatomical parameters also play a role in perioperative morbidity. Preoperative assessment of these factors can aid in surgical planning and patient counselling.