REN and portal hypertension: Ascites, dilutional hyponatremia and hepatorenal syndrome are three clinical manifestations of the same physiopathological disorder: cirrhotic portal hypertension, hyperproduction of nitric oxide, arterial vasodilation with reduction of efficient arterial volume, which have as consequences renal vasoconstriction, sympathetic stimulation, the stimulation of renin–angiotensin–aldosteron system and of vasopressin secretion.