Renal Tubular Acidoses AND Inherited Tubular Disorders

The answer first

Renal tubular acidoses (RTAs) are a group of disorders characterised by a non-anion-gap metabolic acidosis resulting from impaired renal acid-base handling. The FRACP candidate must defend the three types: type 1 (distal) — impaired distal acid secretion (hypokalaemic, urine pH greater than 5.5, nephrocalcinosis/nephrolithiasis); type 2 (proximal) — impaired proximal bicarbonate reabsorption (hypokalaemic, urine pH variable, Fanconi syndrome); and type 4 — hypoaldosteronism or aldosterone resistance (hyperkalaemic, urine pH less than 5.5, common in CKD and diabetes). The answer-first synthesis is: suspect RTA in any non-anion-gap metabolic acidosis with a normal or only mildly reduced eGFR; classify by serum potassium (low in type 1 and 2; high in type 4) and urine pH; treat with bicarbonate replacement (oral sodium bicarbonate 1-2 g tds in type 1 and 2; potassium citrate for hypokalaemia; fludrocortisone 0.1 mg daily or potassium-binding resins in type 4). ^{[1] [3]}

References9ShowHide

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