Expert Opinion :
The common causes of hyperkalemia are:
• high-potassium, low-sodium diets
• High concentrations of potassium in intravenous fluid preparations, such as total parenteral nutrition
• Renal failure
• Type 4 RTA
• Drugs: Potassium-sparing diuretics, spironolactone, amiloride, NSAIDs and ACE inhibitors
• Congenital adrenal hyperplasia (CAH) especially 21-hydroxylase deficiency
• Gordon syndrome or pseudohypoaldosteronism Type II, characterized by hyperkalemia and hypertension
This child is on a milk diet and not on any drugs hence dietary and drugs are not the cause. The child’s renal function tests are normal. Hence the child should now be investigated for Type 4 RTA and CAH. This child’s venous blood gas is normal and urinary 17 hydroxyprogesterone and cortisol are normal. Thus one needs to rule out pseudohypoaldosteronism in this child though the blood pressure is normal. The next step would be to do serum aldosterone and renin levels. The decrease may suggest adrenal insufficiency or pseudohypoaldosteronism.