Acute Kidney Injury Adjusted for Parenchymal Mass Reduction and Long-Term Renal Function after Partial Nephrectomy

We sought to evaluate the association of postoperative acute kidney injury (AKI) adjusted for parenchymal mass reduction with long-term renal function in patients undergoing partial nephrectomy. A total of 629 patients undergoing partial nephrectomy were reviewed. Postoperative AKI was defined by the Kidney Disease: Improving Global Outcomes (KDIGO) serum creatinine criteria, by using either the unadjusted or adjusted baseline serum creatinine level, accounting for renal parenchymal mass reduction. Estimated glomerular filtration rates (eGFRs) were followed up to 61 months (median 28 months) after surgery. The primary outcome was the functional change ratio (FCR) of eGFR calculated by the ratio of the most recent follow-up value, at least 24 months after surgery, to eGFR at 3-12 months after surgery. Multivariable linear regression analysis was performed to evaluate whether unadjusted or adjusted AKI was an independent predictor of FCR. As a sensitivity analysis, functional recovery at 3-12 months after surgery compared to the preoperative baseline was analyzed. Median parenchymal mass reduction was 11%. Unadjusted AKI occurred in 16.5% (104/625) and adjusted AKI occurred in 8.6% (54/629). AKI using adjusted baseline creatinine was significantly associated with a long-term FCR (β = -0.129 ± 0.026, p < 0.001), while unadjusted AKI was not. Adjusted AKI was also a significant predictor of functional recovery (β = -0.243 ± 0.106, p = 0.023), while unadjusted AKI was not. AKI adjusted for the parenchymal mass reduction was significantly associated with a long-term functional decline after partial nephrectomy. A creatinine increase due to remaining parenchymal ischemic injury may be important in order to predict long-term renal functional outcomes after partial nephrectomy.