Renal tubular acidosis (RTA) is characterized by a hyperchloremic normal anion gap metabolic acidosis due to renal tubular defects in acid-base handling.

Comparing RTA Types

Type 1 (Distal RTA)

  • Defect: Impaired distal H+ secretion.
  • Urinary pH: > 5.5 (inability to acidify urine).
  • Serum Potassium: Hypokalemia.
  • Key Association: Nephrolithiasis (due to hypercalciuria).

Type 2 (Proximal RTA)

  • Defect: Impaired proximal HCO3- reabsorption.
  • Urinary pH: < 5.5 (distal acidification intact).
  • Serum Potassium: Hypokalemia.
  • Key Association: Fanconi syndrome.

Type 4 (Hyperkalemic RTA)

  • Defect: Hypoaldosteronism or aldosterone resistance.
  • Urinary pH: < 5.5.
  • Serum Potassium: Hyperkalemia (defining feature).