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Patients With COPD, Acute Kidney Injury at Risk for Hospital Readmission, Study Says


Prevention of acute kidney injury should be top of mind when discharging patients with chronic obstructive pulmonary disease (COPD) from the hospital, according to a recent study.

Patients with acute kidney injury (AKI) and hospitalized for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) were at higher risk of 30- and 90-day readmission, according to a paper published in BMC Nephrology.

Investigators from Massachusetts General Hospital in Boston retrospectively studied 356,990 patients hospitalized with AECOPD in order to determine the link between AKI and readmission risks in this population. Prior studies have indicated a relationship between AKI and AECOPD, but the study authors wrote that there is a gap in the literature for longitudinal studies.

The patients in the analysis were hospitalized adults over the age of 40 years with a principal discharge diagnosis of COPD. The investigators collected data about the patients’ sex, age, race/ethnicity, primary insurance type, estimated household income, patient residence, diagnosis and procedure codes, comorbidities, hospital course, and disposition.

Most of the patients were older (median age: 71 years), male (42%), and white (74%), the study authors determined. During index hospitalization, 7% of patients had a new diagnosis of AKI. The study authors noted that the AKI group was more likely to be older and male.

In total, 16% of patients had at least 1 readmission within 30 days after their primary hospitalization, the investigators found. After 90 days of index hospitalization, 31% of patients had at least 1 readmission, they added.

However, for the AKI patients, the investigators noted a significant difference among all-cause 30- and 90-day readmission rates compared to the overall group. The AKI group had a significantly higher risk of 30-day readmission and a 90-day readmission, the study authors said. This remained true when the investigators further broke the data down to include patients aged 65 years or older only, women only, or patients without chronic kidney disease. After the study authors stratified the data by dialysis use, the AKI group had higher 30- and 90-day readmission rates compared to those without AKI.

The most frequent cause for readmission among patients without AKI was COPD, followed by pneumonia, respiratory failure, and asthma. The study authors learned that the AKI patients were more likely to be readmitted due to non-respiratory diseases, such as sepsis, acute renal failure, or congestive heart failure. The reasons for readmission were not different for 30- or 90-day readmissions, the study authors found after making a list of the top 5.

The study authors also said that patients with AKI and hospitalized for AECOPD had an approximately 2-fold higher mortality rate within 6 months than those without AKI. While prior research has shown that AKI is a risk factor for subsequent infections like tuberculosis and sepsis, the study authors’ findings “warrant clarification,” they said.

“We found that patients with AKI had a 50% higher risk of all-cause readmissions during 30 days after their index hospitalization when compared to those without AKI,” the study authors concluded. “This significant association persisted after the adjustment for potential confounders… For clinicians, our findings underscore the importance of prevention of AKI and post-discharge care in this population.”


Hirayama A, Goto T, Hasegawa K. Association of acute kidney injury with readmissions after hospitalization for acute exacerbation of chronic obstructive pulmonary disease: a population-based study. BMC Nephrol. 2020;21(116) doi: 10.1186/s12882-020-01780-2.

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