Assessing renal recovery after acute kidney injury in elderly patients: a retrospective cohort study

We aimed to examine different acute kidney injury (AKI) recovery patterns in elderly patients and assess their association with long-term outcomes after AKI. This retrospective study included elderly patients admitted to the Chinese PLA General Hospital between 2007 and 2022. Early recovery was defined as renal function recovery documented a week after AKI diagnosis. Recovery of AKI was defined as being alive for over 7 days and when the patient's serum creatinine level returned to below 1.2 times, the baseline value for at least 2 days post-AKI. A total of 1395 elderly patients were enrolled for eventual analysis; their median age was 88 years. Using the Kidney Disease Improving Global Outcomes stage, 51.7%, 25.9%, 22.4% were in stages 1, 2, and 3, respectively. Four patterns are observed. The most common (423; 30.3%) patients showed late recovery after day 7. The remaining patients (337; 24.2%) had never fully recovered; early recovery was sustained (230; 16.5%) during follow-up, but almost as many patients with early recovery had one or more recurrences (255; 18.3%). Patients with different phenotypes had distinct outcomes, and the 1-year survival rates were 79% for early sustained recovery, 64% for recurrent AKI, and less than 41% for patients who had never recovered. Relative to early sustained recovery, late recovery was related to a 2-fold increase in the 1-year mortality. Four different recovery phenotypes were detected based on the clinical course seven days after AKI diagnosis. These phenotypes contribute to the identification of patients suitable for treatment.