Incidence and outcomes of Acute Kidney Injury requiring renal replacement therapy: a retrospective cohort study

Background: Incidence of Acute Kidney Injury (AKI) requiring dialysis is rising globally and is associated with high mortality and morbidity. Aim: To examine the incidence of AKI requiring renal replacement therapy (RRT) in the Tayside region of Scotland and the impact of RRT for AKI on morbidity, mortality and length of hospital stay. Methods: 178 patients (>18 years of age) received acute RRT between 1 January 2012 and 31 December 2012 were retrospectively selected for inclusion into our longitudinal cohort study. Incidence rate was calculated. Length of hospital stay, likely cause of AKI, renal recovery and mortality data were collected for a, during a 1 year follow up period or until death. Chi-square testing was used to compare morbidity and mortality data between subgroups. RRT-free survival and time-until-event (death or RRT) analysis was performed using Kaplan-Meier plots. Cox-regression was used to examine associations between age, sex, diabetes and CKD on survival. Results: Incidence of AKI requiring RRT was 430 per million population per year. Median length of hospital stay was 21 days. In-patient mortality was 36%, mortality at 90 days was 44% and at 1 year 54%. Median time from start of RRT until death or chronic RRT was 90 days (95% CI 14-166). 1-year cumulative RRT-free survival was 26% in the ward, 36% in HDU and 48% in ICU subgroups. Diabetes, gender and CKD at baseline did not affect RRT-free survival in our cohort. A quarter of the cohort regained full renal function and 15% of survivors were on a chronic dialysis programme at 1 year. Conclusions: Our study has given a comprehensive summary of renal outcomes and mortality after a single episode of AKI requiring RRT. Our findings confirm that dialysis-dependent AKI is associated with increased length of hospital stay, high mortality and loss of renal function long term emphasizing the importance of recognition and prevention of AKI.