Blood urea nitrogen to albumin ratio predicts risk of acute kidney injury and in-hospital mortality associated with immunological and surgical diseases: A retrospective analysis of 1994 patients

• The incidence of AKI and in-hospital mortality associated with immunological and surgical diseases is 46.3% and 19.6%, respectively. • BAR, as a marker of inflammation, nutritional status and renal function, is a good predictor of the development of AKI and in-hospital mortality. • BAR ≥ 0.28 and BAR ≥ 0.6were independently associated with the occurrence of AKI and in-hospital mortality, respectively. Acute kidney injury (AKI) is a common complication in hospitalized patients and contributes to high in-hospital mortality. Blood urea nitrogen to albumin ratio (BAR) represents a marker of inflammation, nutritional status, and renal function that predicts the prognosis of different diseases. The aim of this study was to investigate the relationship between BAR and the incidence of AKI and in-hospital mortality in patients with immunological and surgical diseases. We retrospectively enrolled hospitalized patients with immunological and surgical diseases at the West China Hospital of Sichuan University from 1 January 2010 to 1 April 2024. Logistic regression models for AKI and in-hospital mortality were performed. Of the 1994 admissions, AKI occurred in 923 (46.3 %) patients, and 390 (19.6 %) patients died in hospital. In multivariate logistic regression analysis, the predictive role of BAR ≥ 0.28 for AKI remained significant in both adjusted model 1 (OR = 4.879), adjusted model 2 (OR = 4.831), adjusted model 3 (OR = 5.275), adjusted model 4 (OR = 3.039), and adjusted model 5 (OR = 2.709). BAR ≥ 0.6 for in-hospital mortality remained significant in both adjusted model 1 (OR = 5.210), adjusted model 2 (OR = 5.210), adjusted model 3 (OR = 4.861), adjusted model 4 (OR = 3.372), and adjusted model 5 (OR = 3.424). After adjusting for multiple confounders, this association persisted across subgroups. In patients with immunological and surgical diseases, BAR is useful for early identification of patient at high risk of AKI and in-hospital mortality.