Abstract
In order to maintain the homeostasis of life, kidney receives 20% of blood flow (1L/min) in cardiac output. Despite of blood pressure changing, the glomerular filtration rates are kept at 100mL / min. Proximal tubules reabsorb more than 99% of fluid and biogenic substances in solute (i.e. glucose, amino acid and so on) those are essential for maintenance of homeostasis. Complex anatomical structures of kidney contribute to this mechanism that is likely to ultimate recycling system of fluid as well as the efficient waste removal.
Chronic kidney disease (CKD) has been recognized as the great risk factor for cardiovascular events. The interaction so-called “cardio-renal association” may be related to “strain vessel theory” that is based on the anatomical similarity of special vascular structures among brain, heart and kidney. Therefore, the existence of proteinuria suggests impairment of glomeruli as well as cerebra-cardiac vascular damages except cases involving in immunological nephritis. In the guideline of CKD 2012, both estimated Glomerular filtration rate (eGFR) and urinary protein excretion are recognized as risk factor for cardiovascular events. However, the first line therapy for controlling blood pressure changed in CKD patients without proteinuria. The combination of long acting calcium channel blockers with other anti-hypertensive agents are also recommended for CKD patients instead of blind prescription of inhibitors for renin angiotensin system.
To evaluate accurate renal functions is important for appropriate drug therapies in CKD patients. In general, the estimation of eGFR using serum creatinine by MDRD formula is popular but is not always correct. The patients with less muscle mass such as elderly, women, children and bedridden people show lower levels of serum creatinine than we speculate. Therefore, the estimation using serum cystatin C is better for estimation of eGFR, which may be allowed in every 3 month in outpatients.
