Diagnosis of acute kidney injury and its association with in-hospital mortality in patients with infective exacerbations of bronchiectasis: cohort study from a UK nationwide database

Background: Many patients with bronchiectasis have recurrent hospitalisations for infective exacerbations. Acute kidney injury (AKI) is known to be associated with increased in-hospital mortality. This study examined the frequency of AKI, associated risk-factors, and the association of AKI with in-hospital mortality among patients with bronchiectasis. Methods: Anonymised data of patients with non-cystic fibrosis bronchiectasis from the UK Clinical Practice Research Datalink, linked to Hospital Episode Statistics, were used to identify hospitalisations with a primary diagnosis of lower respiratory tract infection (LRTI), from 2004 to 2013. After estimating the proportion of AKI diagnoses, a multivariable logistic regression model was constructed to investigate which background factors were associated with AKI. In-hospital mortality was compared between hospitalisations with and without an AKI diagnosis, with subsequent logistic regression analyses carried out for the association between AKI and in-hospital mortality. Results: Of 7804 hospitalisations due to LRTI observed in 3477 patients with bronchiectasis, 230 hospitalisations involved an AKI diagnosis, an average of 2.9 %. However, the percentage increased from less than 2 % in 2004 to nearly 5 % in 2013. After taking this temporal change into account, AKI was independently associated with older age, male sex, decreased baseline kidney function, previous history of AKI, and a diagnosis of sepsis. In-hospital mortality was 33.0 % (76/230) and 6.8 % (516/7574), in hospitalisations with and without AKI, respectively (P < 0.001). After adjustment for confounding factors, diagnosis of AKI remained associated with in-hospital mortality (Odds ratio 5.52, 95 % confidence interval: 3.62-8.42). Conclusions: Among people with bronchiectasis hospitalised for infective exacerbations, there is an important subgroup of patients who develop AKI. These patients have substantially increased in-hospital mortality and therefore greater awareness is needed.