Hypokalemic RTA | Hyperkalemic RTA | |||
Type 1 RTA (distal RTA) | Type 2 RTA (proximal RTA) | Type 4 RTA (hypoaldosteronism) | Distal tubule sodium transport defects | |
Primary defect | Impaired distal tubule/collecting duct acidification. | Reduced proximal HCO3 reabsorption. | Decreased aldosterone secretion or aldosterone resistance. | Reduced sodium reabsorption unrelated to aldosterone. |
Plasma HCO3 | Variable. May be below 10 mEq/L. | Usually 12 to 20 mEq/L. | Usually greater than 17 mEq/L. | Usually greater than 17 mEq/L. |
Urine pH | Always >5.3. | Variable. Greater than 5.3 during periods of bicarbonaturia usually related to therapeutic increases in serum [HCO3]. Otherwise <5.3. | Variable. Usually greater than 5.3. | Variable. Usually greater than 5.3. |
Plasma potassium | Usually reduced and generally corrects with alkali therapy. | May be normal or reduced; worsened by bicarbonaturia induced by alkali therapy. | Increased. | Increased. |
Urine anion gap (UAG)/urine osmolal gap (UOG) | UAG >20 mEq/L or UOG <150 mosm/kg. Consistent with low urine ammonium concentration. | Variable. | UAG >20 mEq/L or UOG <150 mosm/kg. Consistent with low urine ammonium concentration. | UAG >20 mEq/L or UOG <150 mosm/kg. Consistent with low urine ammonium concentration. |
Urine Ca/Cr ratio | Increased | Normal | Normal | Normal |
Nephrolithiasis/nephrocalcinosis | Yes | No | No | No |
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