772 FACTORS PREDICTING EARLY AND LATE RENAL FUNCTION AFTER LAPAROSCOPIC PARTIAL NEPHRECTOMY

Abstract

INTRODUCTION AND OBJECTIVES: We prospectively assessed the impact of multiple factors affecting early, intermediate and late renal function after LPN. METHODS: Between 2004–2009, sixty-eight patients with 2 functioning renal units undergoing LPN were prospectively analysed. MDRD and Cockcroft Gault-calculated glomerular filtration rates (GFR), MAG-3 renograms with GFR and differential function were obtained at 1) preoperatively 2) immediately post-op ( 3 days) 3) intermediate post-op (6–12wks) and late post-op (one year). The impact of patient demographics, tumour characteristics and surgical factors on functional renal outcomes were assessed. Correlation analysis was first performed using Spearman correlation to elucidate factors correlated with GFR decline. Subsequent multivariate analysis was performed at each of the postop periods. Paired t-test was used to compare baseline GFR and renograms to these outcomes at each of the postoperative time periods. RESULTS: Spearman correlation determined that age, weight, pre-operative GFR, piece size and warm ischemia time (WIT) were correlated with early decline in GFR. However, multivariate analysis showed that in the immediate time period, only tumor weight and WIT were predictive of decreased renal function (p 0.01). As well, in the late post-op period, only the degree of early/intermediate reduction in renal function was predictive of persistent impaired renal function (p 0.00001). Paired t-test analysis showed that there was significant decline in renal function in the immediate and intermediate time points (p 0.001); this decline did not persist at one year, indicating capacity for late renal recovery (p NS). However, paired t-test using nuclear renogram studies showed that there was persistent dysfunction of the affected kidney at one year postop (41.7% vs 49.4% preop; p 0.001). Taken together, this indicates that late renal recovery may occur as a result of compensation from the contralateral renal unit. CONCLUSIONS: This study confirms the negative impact of warm ishemic time upon early renal function post-LPN. Importantly, this is the first study to show that the degree of initial renal functional loss is a key determinant to renal recovery at one year. Additionally, the function of the affected kidney remains compromised at one year, and recovery of renal function is primarily by compensation from the contralateral kidney.