AKI Hospitalizations Found to Be Risk Factor for Postdischarge Adverse Events

Hospitalization for an acute kidney injury (AKI) event was identified as a risk factor for several adverse events after hospital discharge, including hospital readmission and mortality, according to findings presented at Kidney Week 2021.

Hospital admission with an acute kidney injury (AKI) diagnosis was found to be a risk factor for multiple adverse patient outcomes post discharge, according to findings1 presented at the American Society of Nephrology’s Kidney Week 2021 virtual meeting.

The study findings showed hospitalizations from an AKI event were found to substantially increase the risk for subsequent death, hospitalization, heart failure, pneumonia, and sepsis vs non-AKI hospitalization.

“These findings highlight the need for early interventions to mitigate the significant morbidity and mortality burden associated with an AKI event in patients…. While the best post-AKI clinical management regimen is yet to be determined, these results underscore the immediate need for close posthospitalization monitoring of individuals with AKI,” said lead author Ivonne H Schulman, MD, program director for the National Institutes of Health, in a statement.2

Patients with AKI have a higher risk of morbidity and mortality. However, there is a lack of robust data to quantify short- to long-term real world outcomes after patients experience hospitalizations for AKI.

The study investigators derived a synthetic retrospective cohort of hospitalized patients with AKI from Optum Clinformatics to quantify mortality and all-cause or selected hospital readmissions at 90 days and at 1 year after an AKI event. The data were collected for all AKI-related hospitalizations that occurred between January 2007 and September 2020 among patients who went more than 2 years without AKI hospitalization.

Overall, 594 patients were identified, and 509 were included in the analysis. The included patients were propensity score matched with 594,509 control subjects who had been hospitalized for causes unrelated to an AKI event. The mean (SD) age of the AKI cohort was 74.1 (13.1) years. Breaking down the cohort by demographics, 47.6% were women, 73.7% were White, 14.1% were Black, 9.7% were non-White Hispanic, and 2.5% were of Asian descent, which was similar to the control cohort.

Hospitalizations in the 2 years before the index admission occurred in 55.9% of the patients in the AKI cohort and 26.5% in the non-AKI cohort. Additionally, 50.3% of the AKI group had chronic kidney disease (CKD) and 34.9% had heart failure, which was similar to the matched patients in the control group.

The patients in the AKI group had a higher 1-year unadjusted cumulative incidence of all-cause hospital readmission compared with the patients in the control group, regardless of the patients’ history with CKD (P < .01).

When the investigators adjusted for baseline characteristics, AKI-related hospitalization was found to be associated with a higher rate of hospital readmission from any cause (HR, 1.77; 95% CI, 1.75-1.80) compared with the group of patients hospitalized for non-AKI–related events. Also, AKI was associated with higher rates of heart failure (HR, 3.16; 95%CI 3.00-3.32), pneumonia (HR, 1.64; 95% CI, 1.54-1.75), sepsis (HR, 3.06; 95% CI, 2.92-3.21), and end-stage renal disease (HR, 7.88; 95% CI, 1.88-33.07) in the first 90 days following hospital discharge compared with patients in the control group.

Furthermore, both rates for crude and adjusted mortality were higher in the AKI group than the control group at 90 days (HR, 3.04; 95% CI, 2.98-3.09) after discharge and at 365 days (HR, 2.39; 95% CI, 2.36-2.42) after discharge. This pattern persisted when the groups were stratified by whether or not the patients had CKD (P < .01).


1. Schulman IH, NGO DA, Chan KL, et al. Readmission and mortality after acute kidney injury hospitalization. Presented at: ASN Kidney Week 2021; November 4-7, 2021; virtual. Abstract TH-OR06.

2. Acute kidney injury linked to poor patient outcomes after hospital discharge. Press release. The American Society of Nephrology. November 4, 2021. Accessed November 4, 2021. https://www.eurekalert.org/news-releases/933649