Renal Tubular Acidosis

Question 1

How do you test for distal (type 1) RTA to differentiate it from proximal RTA?

Answer 1

Administer IV bicarbonate to raise the serum bicarbonate to 18 to 20mmol/l. In proximal RTA, this results in an increase in urinary pH and the fractional excretion of bicarbonate to 15-20%. This is not observed in dRTA.

Question 2

Why do patients with pRTA respond to an IV bicarbonate load with an increase in their urinary pH while those with dRTA dont? (Key question for nephrologists)

Answer 2

I need to think on this problem

Question 3

How do you calculate the urinary anion gap?

Answer 3

Na+ + K+ - Cl-. A negative urinary anion gap normally indicates that the patient has GI loss of bicarbonate leading to NAGMA.

Question 4

What is the urinary anion gap actually a surrogate for?

Answer 4

Urinary ammonia. This can be measured in some laboratories. It has a reference range of 15-56mmol/l.