Primary hyperaldosteronism is usually suspected when a hypertensive patient is found to be hypokalaemic. This diagnostic clue, however, may be missed unless blood samples are taken properly; sampling without occlusion or muscular exercise is essential, and the plasma must be rapidly separated from the red cells. In addition, the patient should have an adequate sodium intake since, with a low sodium diet, there will be little sodium for distal tubular sodium-potassium exchange and thus hypokalaemia will not persist. Once primary hyperaldosteronism is suspected, the diagnosis must be confirmed by demonstrating suppression of plasma renin activity and elevation of plasma aldosterone levels (Fig. 10.6).
