Hospital-Acquired Acute Kidney Injury and Readmissions

Having to complete excessive paperwork when discharging a patient is an unenviable part of the medical intern’s job description.  I learned the hard way that no patient could be discharged unless the “green core-measure sheet” was filled out.  I would gradually come to appreciate the reason for this emphasis; that conditions listed on that sheet (myocardial infarction, congestive heart failure, pneumonia, COPD) put patients at a high likelihood of “bouncing back” to the hospital within 30 days. And if there is one thing that hospital administrators don’t like, it is excess readmissions. The Accountable Care Act actually requires the federal government to reduce payments to hospitals with high rates of readmission.  That “core-measure sheet” was essentially a way of ensuring that standard evidence-based care was provided to patients to reduce readmission rate, and post-hospital transition of care was appropriate.

Acute kidney injury (AKI) is not on the list of disease states associated with the highest hospital readmission risk. But should it be? That is the question that Koulouridis et al explored in a retrospective cohort study recently published in the AJKD. Reports from the US Renal Data System (USRDS) show a higher 30-day readmission rate among patients with AKI than those without, but this data relies on administrative codes to define AKI.  Furthermore, AKI has been linked with higher risk of hospital readmission in patients with heart failure and after cardiac surgery. Koulouriidis, et al instead used predefined criteria for AKI in a more diverse, unselected population.

The authors conducted a single-center retrospective study of 22,001 patients with mild AKI (defined in the article as “AKI stage 1, in accordance with the KDIGO AKI classification and staging system”). Compared to the non-AKI group, the AKI group had significantly higher 30-day, 60-day, and 90-day readmission rates. Interestingly, the AKI group also was more likely to be readmitted to the hospital within 30 days for cardiovascular-related conditions (heart failure, acute myocardial infarction). The odds ratio for hospital admissions was also independently higher for AKI patients at 30, 60, and 90-days (attenuated results were seen in a propensity score−matched cohort of 5,912 patients, though).


The 30-, 60-, and 90-day hospital readmission rates among patients with and without acute kidney injury (AKI) during the index hospitalization in the (A) primary (unmatched) cohort and (B) secondary (propensity score–matched) cohort. ∗P < 0.001; ∗∗P = 0.05 versus no AKI. Fig 1, Koulouridis et al AJKD, ©National Kidney Foundation.

It is known that AKI is associated with increased hospital mortality, length of stay, and post-acute care. Kouloursis, et al’s analysis, while not demonstrating any causality between AKI and rehospitalization, is hypothesis generating. Systematic studies of transition of care are needed of such patients, especially given that this study showed a possible link between current AKI and future readmission for MI or heart failure. While such studies may take years, these results demand heightened vigilance from primary doctors and nephrologists once such patients get discharged. Perhaps an assessment of kidney function and a comprehensive follow-up visit should be standard care within a few weeks post discharge? Maybe a home-nurse visit to assess for decompensation may help?

While the medical intern may not be thrilled about having to check off one more box on the core-measure sheet, a proactive approach could reduce readmissions and be better for our patients.

Dr. Veeraish Chauhan
eAJKD Contributor

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