Secondary Cardiorenal Syndromes in Children: Focus on Type 3 to 5 Cardiorenal Syndrome

Background: The interaction between the heart and kidneys involves complex mechanisms, leading to a clinical condition known as cardiorenal syndrome (CRS), where dysfunction in one organ leads to impairment of the other. This syndrome can be acute or chronic, affecting both organs simultaneously. Summary: In 2008, the Acute Dialysis Quality Group classified CRS into two main categories: cardiorenal CRS and renocardiac CRS, based on the primary organ affected. Cardiorenal CRS includes two subtypes where heart failure causes kidney injury (types 1 and 2), while renocardiac CRS (types 3 and 4) refers to kidney injury leading to cardiac dysfunction, either from acute kidney injury or chronic kidney disease. Type 5 CRS is termed as secondary CRS which involves both organ dysfunction due to an acute systemic disease, such as sepsis, infections, or chronic conditions like diabetes mellitus. This review examines the cardiovascular involvement in various nephrological diseases commonly seen in clinical practice, with a focus on types 3–5 CRS in children from a nephrology perspective. Key Messages: CRS is common in pediatric patients with cardiac, renal, or systemic conditions and poses a significant risk of mortality. The lack of longitudinal studies or specific biomarkers for the diagnosis, treatment, and follow-up of CRS in children is evident. Aspects such as the development of new biomarkers, ongoing research into neurohormonal mechanisms, meta-analyses, and introduction of algorithms for the follow-up period may reshape patient management. Specific diagnostic tools or therapeutic interventions for CRS management in children should be implemented. Collaborative efforts among pediatricians, cardiologists, and nephrologists are essential for developing effective treatments. Large-scale studies are needed to better understand CRS and develop targeted therapies to improve outcomes for pediatric patients, reducing morbidity and mortality.