Long-Term Impact of the COVID-19 Associated AKI: The Relationship between Kidney Recovery and Mortality in a 10-Month Follow-Up Cohort Study

INTRODUCTION: Coronavirus-2019 disease (COVID-19)-associated acute kidney injury (AKI) and its short and mid-term effect on kidney has been well established in the previous literature, indicating a high number of AKI in hospitalized patients associated with high rates of mortality, followed by high rates of unresolved kidney injury at the time of discharge. However, the long-term impact of AKI and its resulting lack of recovery at the time of discharge has not been investigated. Herein, we sought to explore the possible relationship between AKI and unresolved kidney injury and post-discharge mortality. METHOD: In this cohort study, patients hospitalized with COVID-19 who survived until discharge were followed for a median of 9.6 months. AKI during hospitalization based on the staging according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria and kidney injury status at discharge and other comorbidities and mortality during the follow-up period were recorded. The desired association was investigated using Cox proportional hazards regression after adjustment for potential confounders. RESULT: Among 1,017 discharged patients, 298 patients (29.3%) experienced AKI during hospitalization according to KDIGO criteria, of whom 178 patients (59.7%) were diagnosed with unresolved kidney injury at the time of discharge. After adjusting for potential confounders, Cox regression indicated that AKI stage 3 (hazard ratio (HR): 4.56, 95% confidence interval (CI): 1.89–10.99, p = 0.001) and unresolved kidney injury at the time of discharge (HR: 2.09, 95% CI: 1.18–3.73, p = 0.011) were significantly associated with mortality during the post-discharge period. Additionally, Kaplan-Meier curves for overall survival indicated an increased risk of mortality in patients with stage 2, stage 3 AKI, and unresolved kidney injury at the time of discharge (p < 0.001). CONCLUSION: Overall, it was shown that patients with COVID-19 who develop AKI, mainly stage 2 and 3, and patients with unresolved kidney injury at the time of discharge, were at an increased risk of mortality, even after hospitalization for an extended period of time.