Diagnostic approach to hypokalemia: hypokalemia with total body potassium depletion secondary to extrarenal losses. In the absence of redistribution, measurement of urinary potassium is helpful in determining whether hypokalemia is due to renal or to extrarenal potassium losses. The normal kidney responds to several (3 to 5) days of potassium depletion with appropriate renal potassium conservation. In the absence of severe polyuria, a "spot" urinary potassium concentration of less than 20 mEq/L indicates renal potassium conservation. In certain circumstances (eg, diuretics abuse), renal potassium losses may not be evident once the stimulus for renal potassium wasting is removed. In this circumstance, urinary potassium concentrations may be deceptively low despite renal potassium losses. Hypokalemia due to colonic villous adenoma or laxative abuse may be associated with metabolic acidosis, alkalosis, or no acid-base disturbance. Stool has a relatively high potassium content, and fecal potassium losses could exceed 100 mEq per day with severe diarrhea. Habitual ingestion of clay (pica), encountered in some parts of the rural southeastern United States, can result in potassium depletion by binding potassium in the gut, much as a cation exchange resin does. Inadequate dietary intake of potassium, like that associated ith anorexia or a "tea and toast" diet, can lead to hypokalemia, owing to delayed renal conservation of potassium; however, progressive potassium depletion does not occur unless intake is well below 15 mEq of potassium per day.

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