Renal Biomarkers and Albuminuria Predict Early Adverse Outcomes in Cardiorenal Syndrome Type 2

Background/Objectives: Cardiorenal syndrome type 2 (CRS-2) is characterized by progressive renal dysfunction caused by chronic heart failure (HF) and is associated with increased morbidity and mortality. However, the prognostic value of renal biomarkers in patients with CRS-2 hospitalized for decompensated HF remains unclear. Methods: This prospective observational cohort study included 200 consecutive patients hospitalized for decompensated HF in the Intensive Care Unit of the Clinic for Internal Medicine at the University Clinical Centre Tuzla between April and October 2025. CRS-2 was defined as chronic HF with chronic kidney disease persisting for ≥3 months before admission according to KDIGO criteria. Patients were followed for three months. The primary composite outcome was all-cause mortality or initiation of renal replacement therapy. Results: CRS-2 was identified in 130 patients (65.0%) and was associated with higher in-hospital mortality (32.3% vs. 11.4%, p = 0.002) and three-month mortality (44.6% vs. 21.4%, p = 0.002). Within the CRS-2 subgroup, patients who experienced the primary composite outcome had higher admission levels of cystatin C and urinary albumin-to-creatinine ratio (UACR) and lower estimated glomerular filtration rate (eGFR). ROC analysis demonstrated moderate discriminative ability of cystatin C (AUC 0.739) and UACR (AUC 0.733). In Cox regression analysis, cystatin C (HR 1.534, 95% CI 1.263-1.863, p < 0.001) and UACR (HR 1.003, 95% CI 1.001-1.006, p = 0.001) were significantly associated with the primary composite outcome. Conclusions: Renal dysfunction markers, particularly cystatin C and albuminuria, are associated with early adverse outcomes in CRS-2 patients hospitalized for decompensated HF. Routine assessment of these biomarkers may provide additional prognostic information and support risk assessment in this high-risk population.