Hospital-Acquired Acute Kidney Injury and Hospital Readmission: A Cohort Study

Background Hospital-acquired acute kidney injury (AKI) is associated with increased mortality and resource consumption. Little is known about the association of AKI with short-term hospital readmissions. Study Design Retrospective cohort study. Setting & Participants We investigated whether adult survivors of hospital-acquired AKI were at increased odds for early hospital readmission. Predictor The peak-to-nadir serum creatinine difference during the index hospitalization was used to define AKI according to the KDIGO (Kidney Disease: Improving Global Outcomes) classification and staging system. Measurements Multivariable logistic regression analyses examined the association of AKI with 30-, 60-, and 90-day hospital readmission, adjusting for age, sex, race, Charlson-Deyo comorbidity index score, acute hospital-related factors, common causes of hospitalization, and baseline estimated glomerular filtration rate. Results 3,345 (15%) of 22,001 included patients experienced AKI during the index hospitalization. Compared to the non-AKI group, the AKI group had a significantly higher 30-day hospital readmission rate (11% vs 15%; P < 0.001), which persisted at 60 and 90 days. The AKI group also was more likely to be readmitted to the hospital within 30 days for cardiovascular-related conditions, mainly heart failure ( P < 0.001) and acute myocardial infarction ( P = 0.01). AKI associated independently with higher odds of 30-day hospital readmission (OR, 1.21; 95% CI, 1.08-1.36), which persisted at 60 (OR, 1.15; 95% CI, 1.03-1.27) and 90 days (adjusted OR, 1.13; 95% CI, 1.02-1.25). Results were attenuated in a propensity score−matched cohort of 5,912 patients. Limitations Single-center study of mild forms of AKI; ascertainment bias and outcome misclassification due to the use of administrative codes. Conclusions Our results suggest that survivors of hospital-acquired AKI experience higher odds of early hospital readmission. Transitions of care services may be warranted for such patients to prevent readmissions and reduce health care costs.