Renal tubular acidosis (RTA)

Question 1

Type 1 (distal)

Answer 1

Defect in collecting tubule’s ability to excrete H+. Untreated patents have urine pH >5.5. Associated with hypokalemia. Increased risk for calcium phosphate kidney stones as a result of increased urine pH and bone resorption

Question 2

Type 2 (proximal)

Answer 2

Defect in proximal tubule HCO3- reabsorption. May be seen with Fanconi’s syndrome. Untreated patients typically have urine pH <5.5. Associated with hypokalemia. Increased risk for hypophosphatemic rickets.

Question 3

Type 4 (hyperkalemic)

Answer 3

Hypoaldosteronism or lack of collecting tubule response to aldosterone. The resulting hyperkalemia impairs ammoniagensis in the proximal tubule, leading to decreased buffering capacity and decreased urine pH.