Cardio-Renal Syndrome: Interplay between the Heart and Kidneys

Cardio-renal syndrome (CRS) represents a complex bidirectional interaction between heart and kidney dysfunction, significantly contributing to morbidity and mortality worldwide. CRS encompasses five subtypes, characterized by acute or chronic dysfunction in one organ precipitating dysfunction in the other, driven by hemodynamic, inflammatory, and neurohormonal mechanisms. This literature review synthesizes evidence on the pathophysiology, diagnostic approaches, clinical implications, and therapeutic strategies for CRS, based on systematic searches of PubMed, Scopus, and Web of Science using keywords such as “cardio-renal syndrome,” “heart failure” AND “kidney dysfunction,” and “acute kidney injury” AND “cardiac dysfunction” for studies published between 2015 and 2025. Key mechanisms include renin-angiotensin-aldosterone system (RAAS) overactivation, oxidative stress, and endothelial dysfunction, with elevated biomarkers like neutrophil gelatinase-associated lipocalin (NGAL) detected in 80% of CRS cases. Diagnostic tools such as estimated glomerular filtration rate (eGFR) and cardiac imaging are critical but limited by variability in biomarker assays and overlapping clinical presentations. Therapies like RAAS inhibitors and diuretics reduce mortality by 15–25% in CRS type 2, but their efficacy varies across subtypes. This review highlights the need for standardized diagnostics, integrated risk models, and novel therapies to address the heart-kidney axis effectively.