REN and chronic kidney disease: The high incidence of CVD in ESKD relates to traditional CVD-risk factors such as hypertension and diabetes (often present in CKD patients), but also CKD-specific alterations that may cause (micro)vascular dysfunction: increases in circulating levels of waste products such as uremic toxins (e.g., asymmetric dimethylarginine (ADMA), altered renal endocrine factors (renin-angiotensin-aldosterone-system, vitamin D, erythropoietin), anemia, serum calcium and phosphate levels [16,17,18].