genitourinary disorders
Renal Tubular Acidosis
Diagnosis of RTA
Suspected in patients with metabolic acidosis with normal anion gap or with unexplained hyperkalemia Serum and urine pH, electrolyte levels, and osmolalities Often, testing after stimulation (eg, with ammonium chloride, bicarbonate, or a loop diuretic) RTA is suspected in any patient with unexplained Metabolic Acidosis (low plasma bicarbonate and low blood pH) with normal anion gap. Type 4 RTA should be suspected in patients who have persistent hyperkalemia with no obvious cause, such as potassium supplements, potassium-sparing diuretics, or Type 1 RTAis confirmed by a urine pH that remains>5.5 during systemic acidosis. The acidosis may occur spontaneously or be induced by an acid load test (administration of ammonium chloride 100 mg/kg orally). Normal kidneys reduce urine pH to<5.2 within 6 hours of acidosis. Type 2 RTAis diagnosed by measurement of the urine pH and fractional bicarbonate excretion during a bicarbonate infusion (sodium bicarbonate0.5 to 1.0 mEq/kg/hour [0.5 to 1.0 mmol/L] IV). In type 2, urine pH rises above 7.5, and the fractional excretion of bicarbonate is>15%. Because IV bicarbonate can contribute to hypokalemia, potassium supplements should be given in adequate amounts before infusion. Type 4 RTAis confirmed by a history of a condition that could be associated with type 4 RTA, chronically elevated potassium, and normal or mildly decreased bicarbonate. In most cases plasma renin activity is low,aldosteroneconcentration is low, and cortisol is normal. 