Renal Tubular Acidosis

Question 1

Renal Tubular acidosis is associated with what blood gas finding?

Answer 1

hyperchloraemic metabolic acidosis
(normal anion gap).

Question 2

Describe the four types of Renal Tubular Acidosis

Answer 2

RTA1 - distal
RTA2 - proximal
RTA3 - mixed
RTA4 - hyperkalaemic

Question 3

Pathophysiology of RTA1

Answer 3

• inability to generate acidic urine (secrete H+) in distal tubule
  => hypokalaemia
  => nephrocalcinosis
  => renal stones

Question 4

What often causes RTA type 1(distal)?

Answer 4

• idiopathic
• Rheumatoid arthritis
• SLE
• Sjogren’s
• amphotericin B toxicity
• analgesic nephropathy

Question 5

Pathophysiology of RTA2

Answer 5

• decreased HCO3- reabsorption in proximal tubule
  => hypokalaemia
  => osteomalacia

Question 6

Causes of RTA2 (proximal)

Answer 6

• idiopathic
• Fanconi syndrome
• Wilson’s disease
• cystinosis
• tetracyclines
• carbonic anhydrase inhibitors (acetazolamide, topiramate)

Question 7

Pathophysiology of RTA3

Answer 7

• carbonic anhydrase II deficiency
  => hypokalaemia

Question 8

Pathophysiology of RTA4

Answer 8

• reduction in aldosterone
  => reduction in proximal tubular ammonium excretion

=> HYPERkalaemia

Question 9

Causes of RTA4 (hyperkalaemic)

Answer 9

• hypoaldosteronism
• diabetes