From COVID-19-Associated Acute Kidney Injury to Long-Term Kidney Dysfunction: Recovery Phenotypes, Risk Stratification, and Post-COVID Renal Surveillance

Background: COVID-19-associated acute kidney injury (AKI) is common in severe disease, but its long-term kidney implications are heterogeneous and incompletely defined. Objective: To synthesize recovery phenotypes and longitudinal outcomes, reconcile conflicting evidence on whether COVID-associated AKI differs from other-cause AKI, and set out implications for surveillance and management. Methods: The evidence base was assembled through a targeted PubMed/MEDLINE search for COVID-19 and kidney dysfunction (January 2020 to August 2026), hand-searching of reference lists, and direct retrieval of pivotal longitudinal cohorts and clinical practice guidelines. Longitudinal cohorts and comparative studies were prioritized. Findings: AKI severity, duration, kidney replacement therapy, lower baseline estimated glomerular filtration rate (eGFR), and incomplete early recovery consistently identify patients at greatest risk. Longitudinal studies disagree on whether COVID-AKI confers more risk than AKI from other illnesses: early cohorts reported steeper eGFR loss, whereas a later 9624-patient cohort found lower adjusted major adverse kidney events. This divergence reflects differences in kidney reference point, outcome construction, ascertainment, and handling of competing death rather than genuine contradiction. Population studies show long-term kidney failure is concentrated after hospitalization and severe disease. Candidate biomarkers remain investigational. Conclusions: Post-COVID kidney risk is severity- and phenotype-dependent rather than universal. Follow-up is most defensible after hospitalized AKI, incomplete recovery, advanced chronic kidney disease (CKD), dialysis, or transplantation and applies existing post-AKI guidance rather than a COVID-specific schedule. Survivors who meet Kidney Disease: Improving Global Outcomes (KDIGO) criteria for CKD at three months, namely a GFR below 60 mL/min/1.73 m2 or a persistent marker of kidney damage, become eligible for guideline-directed therapy, though no trial has enrolled on recent AKI. Prospective studies should test whether structured follow-up improves outcomes.