Acute kidney injury as an independent predicting factor for stage 3 or higher chronic kidney disease after nephrectomy.

BACKGROUND: The association between postoperative acute kidney injury (AKI) and long-term renal function after nephrectomy has not been fully explored, with accurate prognostic models in which AKI is an independent predicting variable still being absent. METHODS: We conducted a retrospective study of 528 patients who underwent unilateral radical nephrectomy or partial nephrectomy owing to renal cell carcinoma between January 2013 and December 2016. Postoperative AKI was defined as an absolute increase in serum creatinine level by 0.3 mg/dl or ≥5 0% increase from the preoperative value within 48 hours after surgery. The endpoint was the time to the incident stage 3 or higher chronic kidney disease (defined as eGFR<60 ml/min/1.73m²), or any claim for initiation of dialysis. Cox proportional hazards regression analysis was conducted to construct the final model. Internal validation was performed using 10-fold cross-validation. The model was evaluated in discrimination by Harrell's C-index and area under curve (AUC) values, and calibration by calibration plots. RESULTS: Five hundred twenty-eight patients were finally enrolled in the study cohort, and the median follow-up period was 38 months. Among 528 admitted patients, 232 (43.9%) developed AKI, and stage 3 or higher CKD occurred in 47 (8.9%) patients during the follow-up time, with 33 in 47 patients (70.2%) having postoperative AKI. AKI was significantly correlated with poor prognosis of renal function (HR = 3.079, P < 0.001). After the adjustment of conventional predictors, AKI was still independently related to kidney function deterioration, and the correlation was influenced by the severity of AKI. Five variables were selected to establish the prognostic model, including age, surgery type, preoperative estimated glomerular filtration rate, preoperative blood urea nitrogen, and postoperative AKI. The model had good discrimination, with the Harrell's C-index of 0.92 (95% CI 0.89-0.95), and AUC values varying from 87.7 to 95.7 at different time points. CONCLUSIONS: AKI during the perioperative period is an independent predicting factor of stage 3 or higher CKD after nephrectomy.