Understanding Renal Tubular Acidosis (RTA) for Internal Medicine Boards
TL;DR Summary: A comprehensive educational breakdown comparing Type 1, Type 2, and Type 4 renal tubular acidosis including diagnostic flowcharts.
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).
Discussion & Comments