30-day readmissions after an acute kidney injury hospitalization

Background — The risk of hospital readmission in acute kidney injury (AKI) survivors is not well understood. We estimated the proportion of AKI patients who were rehospitalized within 30 days and identified characteristics associated with hospital readmission.

Methods — We conducted a population-based study of patients who survived a hospitalization complicated by AKI from 2003-2013 in Ontario, Canada. The primary outcome was 30-day hospital readmission. We used a propensity score model to match patients with and without AKI, and a Cox proportional hazards model with death as a competing risk to identify predictors of 30-day readmission.

Results — We identified 156,690 patients who were discharged from 197 hospitals after an episode of AKI. In the subsequent 30 days, 27,457 (18%) patients were readmitted, 15,988 (10%) visited the emergency department, and 7480 (5%) died. We successfully matched 111,778 patients with AKI 1:1 to patients without AKI. The likelihood of 30-day readmission was higher in AKI patients than those without AKI (hazard ratio [HR] 1.53, 95% CI 1.50-1.57). Factors most strongly associated with 30-day rehospitalization were the number of hospitalizations in the preceding year (adjusted HR 1.45 for ≥ 2 hospitalizations, 95% CI 1.40-1.51) and receipt of inpatient chemotherapy (adjusted HR 1.44, 95% CI 1.32-1.58).

Conclusions — One in five patients who survive a hospitalization complicated by AKI is readmitted in the next 30 days. Better strategies are needed to identify and care for AKI survivors in the community.