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Question 16#

The following are true for renal tubular acidosis (RTA) except:

a. Type 1 RTA is the failure of H+ secretion in the distal nephron tubules
b. Type 1 RTA is the failure of H+ secretion is characterised by hyperchloraemic metabolic acidosis (normal anion gap)
c. Type 1 RTA typically form calcium phosphate stones
d. Treatment of distal RTA should not be undertaken with potassium citrate, which has the effect of increasing urine pH
e. The ammonium chloride acidification test with a urinary pH > 5.5 being indicative of RTA

Correct Answer is D

Comment:

Answer D

Renal tubular acidosis (RTA) is a family of diseases characterised by failure of tubular H+ secretion and urinary acidification. Type 1 RTA is the failure of H+ secretion in the distal nephron tubules and is characterised by hyperchloraemic metabolic acidosis (normal anion gap), a high urinary pH (>5.5, alkaline urine) and low serum bicarbonate. The disease also has low sodium levels, there is a female predominance and due to the low citrate they are predisposed to calcium stones and in particular calcium phosphate stones. The condition is treated with potassium citrate solution. In Type 2 RTA, there is a failure of bicarbonate reabsorption (loss) in the proximal tubule of the nephron with similar characteristics to Type 1 RTA except citrate levels are normal therefore no stones form. The ammonium chloride acidification test (100 mg/kg) is one of the tests used to diagnose RTA with a urinary pH of >5.5 indicative of a failure of urinary acidification, and supportive of the diagnosis of dRTA.

Treatment of distal RTA include correction of the metabolic acidosis, with potassium citrate being one of the treatment options.