Association of the Blood Urea Nitrogen-to-Albumin Ratio with Clinical Outcomes in Patients with Cardiorenal Syndrome Presenting to the Emergency Department: A Retrospective Study

Abstract Background Cardiorenal syndrome (CRS) is a complex clinical condition characterized by bidirectional cardiac and renal dysfunction and associated with high morbidity and mortality. Given the limitations of existing cardiac and renal biomarkers, readily accessible prognostic indicators are needed. This study aimed to evaluate the association of the blood urea nitrogen-to-albumin ratio (BAR) with in-hospital mortality, intensive care unit (ICU) admission, and hemodialysis requirement in patients with CRS presenting to the emergency department. Methods This single-center retrospective study included 201 adults with cardiorenal syndrome presenting to a tertiary emergency department between May 1, 2023, and April 30, 2025. Clinical and laboratory characteristics were compared using Welch’s t-test or the Mann–Whitney U test. Receiver operating characteristic (ROC) analysis evaluated discrimination for hemodialysis within 48 hours; paired areas under the curve (AUCs) were compared using DeLong’s test. Results Mean age was 73.22 ± 11.99 years (n = 200), and 103 patients (51.2%) were female. In-hospital mortality occurred in 67 patients (33.3%), ICU admission in 105 (52.2%), and hemodialysis within 48 hours in 58 (28.9%). Median BAR was higher in patients requiring hemodialysis (2.51 vs. 1.75; p < 0.001). The AUC was 0.694 (95% confidence interval, 0.609–0.779). A cutoff of 2.64 yielded 48.3% sensitivity, 88.1% specificity, and a Youden index of 0.364. BAR did not differ significantly by mortality (p = 0.207) or ICU admission (p = 0.209). Its AUC was not significantly different from that of BUN (0.709; p = 0.230), but was higher than that of albumin (0.476; p < 0.001). Conclusions Higher BAR was associated with early hemodialysis requirement in unadjusted analyses, but superiority over BUN alone was not demonstrated. BAR did not differ significantly by mortality or ICU admission. Independent prognostic value and clinical utility require further evaluation.