Acute kidney injury incidence, recovery, and long-term kidney outcomes among hospitalized patients with COVID-19 and influenza.

Introduction Acute kidney injury (AKI) is a common complication in patients with severe COVID-19. We sought to compare the AKI incidence and outcomes among patients hospitalized with COVID-19 and with influenza. Methods This was a retrospective cohort study of patients with COVID-19 hospitalized between March and May 2020 and historical controls hospitalized with influenza A or B between January 2017 and December 2019 within a large health care system. Cox proportional hazards models were used to compare the risk of AKI during hospitalization. Secondary outcomes included AKI recovery, mortality, new-onset chronic kidney disease (CKD), and ≥25% estimated glomerular filtration rate (eGFR) decline. Results A total of 2425 patients were included; 1091 (45%) had COVID-19, and 1334 (55%) had influenza. The overall AKI rate was 23% and 13% in patients with COVID-19 and influenza, respectively. Compared with influenza, hospitalized patients with COVID-19 had an increased risk of developing AKI (adjusted hazard ratio [aHR] = 1.58; 95% confidence interval [CI], 1.29–1.94). Patients with AKI were more likely to die in the hospital when infected with COVID-19 versus influenza (aHR = 3.55; 95% CI, 2.11–5.97). Among patients surviving to hospital discharge, the rate of AKI recovery was lower in patients with COVID-19 (aHR = 0.47; 95% CI, 0.36–0.62); however, among patients followed for ≥90 days, new-onset CKD (aHR = 1.24; 95% CI, 0.86–1.78) and ≥25% eGFR decline at the last follow-up (aHR = 1.36, 95% CI, 0.97–1.90) were not significantly different between the cohorts. Conclusion AKI and mortality rates are significantly higher in patients with COVID-19 than influenza; however, kidney recovery among long-term survivors appears to be similar.