COVID-19-Associated Acute Kidney Injury and Longitudinal Kidney Outcomes.

Importance: COVID-19 infection is associated with a high incidence of acute kidney injury (AKI). Although rapid kidney function decline has been reported in the first few months after COVID-19-associated AKI (COVID-AKI), the longer-term association of COVID-AKI with kidney function remains unknown. Objective: To assess long-term kidney outcomes of patients who had COVID-19-associated AKI. Design, Setting, and Participants: This was a retrospective longitudinal multicenter cohort study conducted in a large hospital system using electronic health records data on adult hospitalized patients with AKI and COVID-19 or other illnesses. Included patients were hospitalized during the COVID-19 pandemic (March 2020-June 2022), were screened for SARS-CoV-2, had AKI, and survived to discharge, or had been hospitalized during the 5 years before the pandemic (October 2016-January 2020), had a positive influenza A or B test result, had AKI, and survived to discharge. Patients were followed up for a maximum of 2 years after hospital discharge. Data analyses were performed from December 2022 to November 2023. Exposure: COVID-19 and influenza. Main Outcomes and Measures: The primary outcome was major adverse kidney events (MAKE), defined as a composite of mortality and worsened kidney function (estimated glomerular filtration rate [eGFR] decline by ≥25% from discharge eGFR or kidney failure requiring dialysis). Multivariable time-to-event analyses were performed to compare MAKE between individuals with COVID-AKI and those who had AKI associated with other illnesses hospitalized during the same period. For further comparison, this outcome was assessed for a historic cohort of patients with influenza-associated AKI. Results: The study cohort included 9624 hospitalized patients (mean [SD] age, 69.0 [15.7] years; 4955 [51.5%] females) with AKI, including 987 patients with COVID-AKI, 276 with influenza-associated AKI, and 8361 with AKI associated with other illnesses (other-AKI). Compared with the other 2 groups, patients with COVID-19-associated AKI were slightly younger in age, had a higher baseline eGFR, worse baseline comorbidity scores, higher markers of illness severity, and longer hospital stay. Compared with the other-AKI group, the COVID-AKI group had lower MAKE (adjusted hazard ratio [aHR], 0.67; 95% CI, 0.59-0.75) due to lower all-cause mortality (aHR, 0.31; 95% CI, 0.24-0.39) and lower rates of worsened kidney function (aHR, 0.78; 95% CI, 0.69-0.88). Conclusions and Relevance: The findings of this multicenter cohort study indicate that survivors of hospitalization with COVID-AKI experience lower rates of MAKE, long-term kidney function decline, and mortality compared with patients with AKI associated with other illnesses.

Association of clinical characteristics with urine uromodulin in children with chronic kidney disease.

BACKGROUND: Uromodulin is the most abundant protein in the urine of healthy adults, and higher urine concentrations mark better tubular health. Greater kidney size and function are predictors of higher uromodulin levels in adults. Urine uromodulin has not yet been studied in children with chronic kidney disease (CKD). Thus, we sought to determine the relationship between age and kidney function with urine uromodulin levels in children with CKD. METHODS: In the CKD in Children (CKiD) cohort, we utilized multivariable linear regression to evaluate the relationship of age and eGFR with urine uromodulin levels. The primary outcome was uromodulin indexed to urine creatinine (Umod/Cr, mg/g), which was log2-transformed given its skewed distribution. RESULTS: Among 677 CKiD participants, the median age was 11.8 years (8.2-15.3), the median eGFR was 49 ml/min/1.73 m2 (37-63), the etiology of CKD was glomerular disease in 31%, and the median Umod/Cr level was 0.114 mg/g (0.045-0.226). In the multivariable models, each one-year older age was associated with 0.18 (12%) lower log2(Umod/Cr) and 0.20 (13%) lower log2(Umod/Cr) among those with non-glomerular and glomerular disease, respectively (p < 0.001). However, we did not find a statistically significant association between eGFR and Umod/Cr in either participants with non-glomerular or glomerular disease (p = 0.13 and p = 0.58, respectively). CONCLUSIONS: Among children with CKD, older age is significantly associated with lower Umod/Cr, independent of eGFR. Further studies are needed to comprehensively evaluate age-specific reference ranges for urine uromodulin and to evaluate the longitudinal relationship of uromodulin with both age and eGFR in children with CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.