Differing Between Diarrhea and Metabolic Acidosis

In patients that have a non-anion get metabolic acidosis and are having diarrhea and hypokalemia we expect that the kidney should be trying to hold on to as much potassium as it can so urine potassium should be very low or less than 15. In a patient that has an RTA the kidney is not responding appropriately to either acidosis or to potassium loss so we expect higher urine potassium and the urine potassium of greater than 15. And so this mechanism I really like because it is really looking at overactivity of aldosterone. So in a patient withhypokalemia and metabolic alkalosis the question is where is that extra aldosterone coming from and if we can