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. (Reprinted with permission from Mount DB, Zandi-Nejad K: Disorders of potassium balance. In: Brenner and Rector's The Kidney, 8th ed, Brenner BM [ed]. Philadelphia, Saunders, 2008.)