RTA

Question 1

Which of the following is the most characteristic finding in Proximal Renal Tubular Acidosis (Type 2 RTA)?
A) Hyperkalemia
B) Persistent urine pH >5.5 despite acidemia
C) Glycosuria, aminoaciduria, and phosphaturia (Fanconi syndrome)
D) Low urinary ammonium excretion

Answer 1

Answer: C) Glycosuria, aminoaciduria, and phosphaturia (Fanconi syndrome)

Rationale:
Proximal RTA (Type 2) is often due to generalized proximal tubular dysfunction, which is characteristic of Fanconi syndrome. This results in glycosuria, aminoaciduria, and phosphaturia. Hyperkalemia (A) is more characteristic of Type 4 RTA. Persistent urine pH >5.5 despite acidemia (B) is seen in distal RTA (Type 1). Low urinary ammonium excretion (D) is more common in distal RTA and Type 4 RTA due to impaired acid excretion.

Question 2

A patient with Proximal RTA (Type 2) is given sodium bicarbonate therapy. What is the most likely electrolyte abnormality to develop?
A) Hyperkalemia
B) Hypokalemia
C) Hypernatremia
D) Hypercalcemia

Answer 2

Answer: B) Hypokalemia

Rationale:
In proximal RTA, bicarbonate therapy enhances the delivery of bicarbonate to the distal nephron, which stimulates renal potassium secretion, leading to hypokalemia. Hyperkalemia (A) is characteristic of Type 4 RTA. Hypernatremia (C) and hypercalcemia (D) are not primary findings in proximal RTA.

Question 3

Which of the following findings is characteristic of distal (Type 1) RTA?
A) Hypokalemia, nephrocalcinosis, and inappropriately high urine pH
B) Hyperkalemia, low urine pH, and high ammonium excretion
C) High urine pH, hyperkalemia, and nephrolithiasis
D) Low urine pH, low urinary ammonium excretion, and hyperkalemia

Answer 3

Answer: A) Hypokalemia, nephrocalcinosis, and inappropriately high urine pH

Rationale:
Distal RTA (Type 1) is associated with hypokalemia, nephrocalcinosis, and an inappropriately high urine pH (>5.5) due to impaired hydrogen ion secretion in the distal tubule. Hyperkalemia (B and C) is more characteristic of Type 4 RTA. Low urine pH (D) is not a feature of distal RTA.

Question 4

Which type of renal tubular acidosis is associated with hyperkalemia despite only a modest reduction in glomerular filtration rate (GFR)?
A) Proximal RTA (Type 2)
B) Distal RTA (Type 1)
C) Generalized distal RTA (Type 4)
D) None of the above

Answer 4

Answer: C) Generalized distal RTA (Type 4)

Rationale:
Type 4 RTA is characterized by hyperkalemia that is disproportionate to the reduction in GFR due to impaired potassium and acid secretion. This is commonly seen in conditions such as diabetic nephropathy and chronic tubulointerstitial disease. Proximal RTA (A) and distal RTA (B) are typically associated with hypokalemia.