BACKGROUNDCardio-renal syndrome, characterized by simultaneous cardiac and renal impairment, presents significant challenges in patient prognostication and management. This study aimed to investigate the C-reactive protein-to-albumin ratio (CRP/Albumin ratio) as a prognostic marker in patients with cardiorenal syndrome.METHODSThis observational cohort study included consecutive patients hospitalized for cardiorenal syndrome. Baseline demographics, medical history, and prior medication use were recorded. Routine laboratory tests, including serum CRP and albumin, were performed on the first hospitalization day, and their ratio was calculated. Patients were divided into two groups based on the median CRP/Albumin ratio. A transthoracic echocardiographic examination was conducted for each subject. The primary endpoint was in-hospital mortality.RESULTSA total of 135 patients were enrolled (median age: 79 years, median hospitalization: 9 days, 64.5% male). The population was categorized into two groups: Group 1 with CRP/Albumin ratio < 576 and Group 2 with CRP/Albumin ratio ≥ 576. Baseline characteristics and medication use prior to admission were similar, except for a higher prevalence of diabetes and coronary artery disease in Group 2. Co-existing infection and oliguria/anuria were more common in Group 2. There were no significant differences in laboratory parameters and echocardiographic findings. Cox regression analysis revealed that a CRP/Albumin ratio ≥ 576 was an independent predictor of in-hospital mortality (hazard ratio: 3.09, 95% CI 1.22-7.81, p = 0.017), even after adjusting for confounders.CONCLUSIONAn elevated CRP/Albumin ratio was associated with a higher risk of in-hospital mortality in patients with cardiorenal syndrome, highlighting the critical role of inflammation in this population.