Objective: This study aimed to identify predictive factors for percutaneous nephrolithotomy (PCNL) bleeding risks. With better risk stratification, bleeding in high-risk patient can be anticipated and facilitates early identification.

Methods: A prospective observational study of PCNL performed at our institution was done. All adults with radio-opaque renal stones planned for PCNL were included except those with coagulopathy, planned for additional procedures. Factors including gender, co-morbidities, body mass index, stone burden, puncture site, tract dilatation size, operative position, surgeon's seniority, and operative duration were studied using stepwise multivariate regression analysis to identify the predictive factors associated with higher estimated hemoglobin (Hb) deficiency.

Results: Overall, 4.86% patients (n=7) received packed cells transfusion. The mean estimated Hb deficiency was 1.3 (range 0-6.5) g/dL and the median was 1.0 g/dL. Stepwise multivariate regression analysis revealed that absence of hypertension (p=0.024), puncture site (p=0.027), and operative duration (p=0.023) were significantly associated with higher estimated Hb deficiency. However, the effect sizes are rather small with partial eta-squared of 0.037, 0.066, and 0.038, respectively. Observed power obtained was 0.621, 0.722, and 0.625, respectively. Other factors studied did not correlate with Hb difference.

Conclusion: Hypertension, puncture site, and operative duration have significant impact on estimated Hb deficiency during PCNL. However, the effect size is rather small despite adequate study power obtained. Nonetheless, operative position (supine or prone), puncture number, or tract dilatation size did not correlate with Hb difference. The mainstay of reducing bleeding in PCNL is still meticulous operative technique. Our study findings also suggest that PCNL can be safely done by urology trainees under supervision in suitably selected patient, without increasing risk of bleeding.