The diagnostic approach to hyperkalemia. See text for details. ACEI, angiotensin-converting enzyme inhibitor; acute GN, acute glomerulonephritis; ARB, angiotensin II receptor blocker; ECV, effective circulatory volume; LMW heparin, low-molecular-weight heparin; PHA, pseudohypoaldosteronism; TTKG, transtubular potassium gradient. (From Mount DB, Zandi-Nejad K: Disorders of potassium balance, in The Kidney, 8th ed, BM Brenner [ed]. Philadelphia, Saunders, 2008; with permission.)