REN and Hypokalemia: Renin measurement is not widely available clinically for cats; therefore, the criteria of elevated plasma aldosterone concentrations in the presence of otherwise unexplained hypokalemia and an adrenal mass on imaging were used, which is the current diagnostic standard for cats.62,63 It is of interest to us that in our recent prospective study of PA in humans,18 only 3 of 170 patients had a plasma Na+ <140 mmol/L.