Recovery of Kidney Function After Acute Kidney Disease - a Multi-Cohort Analysis

Background
There are no consensus definitions for evaluating kidney function recovery after acute kidney injury (AKI) and acute kidney disease (AKD), nor is it clear how recovery varies across populations and clinical subsets. We present a federated analysis of four population-based cohorts from Canada, Denmark, and Scotland, 2011-2018.
Methods
We identified incident AKD defined by serum creatinine changes within 48 hours, 7 days, and 90 days based on KDIGO AKI and AKD criteria. Separately, we applied changes up to 365 days to address widely used e-alert implementations that extend beyond the KDIGO AKI and AKD timeframes. Kidney recovery was based on resolution of AKD and a subsequent creatinine measurement below 1.2x baseline. We evaluated transitions between non-recovery, recovery, and death up to one year; within age, sex, and comorbidity subgroups; between subset AKD definitions; and across cohorts.
Results
There were 464,868 incident cases, median ages 67-75 years. At one year, results were consistent across cohorts, with pooled mortalities for creatinine changes within 48 hours, 7 days, 90 days and 365 days (and 95% CI) of 40% (34-45%), 40% (34-46%), 37% (31-42%), 22% (16-29%) respectively; and non-recovery of kidney function of 19% (15-23%), 30% (24-35%), 25% (21-29%), 37% (30-43%) respectively. Recovery by 14 and 90 days was frequently not sustained at one year. Older males and those with heart failure or cancer were more likely to die than experience sustained non-recovery, whereas the converse was true for younger females and those with diabetes.
Conclusion
Consistently across multiple cohorts, based on one-year mortality and non-recovery, KDIGO AKD (up to 90 days) is at least prognostically similar to KDIGO AKI (7 days), and covers more people. Outcomes associated with AKD vary by age, sex and comorbidities such that older males are more likely to die, and younger females are less likely to recover.