REN and hypertensive disorder: The etiology of hypertension in CKD is complicated and the result of a number of factors, including decreased glomerular mass, decreased sodium excretion and an extracellular volume expansion, an overactive sympathetic nervous system that increases peripheral vasoconstriction, an activation of hormones including the renin-angiotensin-aldosterone system (RAAS), and endothelial dysfunction [52].