Renal Tubular Acidosis

Question 1

What is Renal Tubular Acidosis

Answer 1

Renal tubular acidosis (RTA) comprises a series of disorders characterized by impaired acid handling.

It manifests as normal anion gap metabolic acidosis (NAGMA) with maintained renal function. The condition comes in three main types, namely Type 1 (distal), Type 2 (proximal), and Type 4 (hyperkalaemic)

Question 2

Whats is Type 1 RTA ? (distal)

Answer 2

-inability to generate acid urine (secrete H+) in the distal tubule

-causes hypokalaemia

-complications include nephrocalcinosis and renal stones

-causes include :
idiopathic rheumatoid arthritis,
SLE
Sjogren’s
amphotericin B toxicity
analgesic nephropathy

Question 3

What is Type 2 RTA? (proximal)

Answer 3

decreased HCO3- reabsorption in the proximal tubule

causes hypokalaemia

complications include osteomalacia

causes include idiopathic as part of Fanconi syndrome
Wilson’s disease
cystinosis
outdated tetracyclines
carbonic anhydrase inhibitors (acetazolamide, topiramate)

Question 4

What is Type 3 RTA (mixed)?

Answer 4

extremely rare

caused by carbonic anhydrase II deficiency

results in hypokalaemia

Question 5

What is Type 4 RTA (hyperkalaemic)?

Answer 5

reduction in aldosterone leads in turn to a reduction in proximal tubular ammonium excretion

causes hyperkalaemia

causes include hypoaldosteronism, diabetes

Question 6

NAGMA + raised urine pH + history of nephrolithiasis

(dry eyes + dry mouth)

Answer 6

RTA Type 1

• Sjogren’s - associated with renal tubular acidosis type 1

Question 7

How do I calculate the anion gap?

Answer 7

(Na+ + K+) - (HCO3- + Cl-)

Question 8

Normal anion gap metabolic acidosis (NAGMA) range?

Answer 8

The normal range is 10-18mmol/L.