Clinical Chemistry

Question 1

What is typical of type 1 RTA?

Answer 1

*Renal Tubular Acidosis
*Failure to acidify urine after acid load is typical of type 1 RTA.
type 1 (distal)
*Type 1 RTA is caused by insufficient H+ excretion at the distal tubule. Therefore, the kidney is unable to eliminate excessive acid and acidify the urine in situations of systemic acidosis.

Question 2

What is typical of type 2 RTA?

Answer 2

Losses of bicarbonate in the proximal renal tubule are characteristic of type 2 RTA
2 (proximal)

Question 3

What is RTA?

Answer 3

*RTA = renal tubular acidosis
(kidney function)
RTA is defined as hyperchloremic metabolic acidosis (normal anion gap) caused by urinary losses of acid as a result of tubular defects. It can be subclassified as type 1 (distal), 2 (proximal), and 4 (hyporeninemic hypoaldosteronism). Type 3 refers to a mixed proximal and distal condition and does not represent a distinct clinical entity.

Question 4

Define type 1 RTA

Answer 4

Type 1 RTA is caused by insufficient H+ excretion at the distal tubule. Therefore, the kidney is unable to eliminate excessive acid and acidify the urine in situations of systemic acidosis.
*Since acid excretion is reduced, sodium preferably exchanges with potassium at the distal tube, and hypokalemia can be present.

Question 5

What can cause type 1 RTA?

Answer 5

Causes include calcium-induced tubular damage,
drugs (e.g., lithium, amphotericin B, nonsteroidal anti-inflammatory drugs),
toxins (toluene),
paraproteins,
autoimmune disorders,
genetic defects in distal transporters (SLC4A1, ATP6V1B1, ATP6V0A4).

Question 6

Sodium and potassium in type 1 RTA

Answer 6

Since acid excretion is reduced, sodium preferably exchanges with potassium at the distal tube, and hypokalemia can be present.
*In hyperkalemic type I RTA, the sodium load to the distal tube is reduced and therefore potassium secretion is impaired. This can result from any cause of marked volume depletion with enhanced proximal tubule reabsorption of sodium or from inhibition of distal sodium reabsorption with potassium-sparing diuretics, lithium, trimethoprim, sickle cell nephropathy, lupus nephritis, or urinary obstruction.

Question 7

Is type 1 RTA always hypokalemic?

Answer 7

No
*In hyperkalemic type I RTA, the sodium load to the distal tube is reduced and therefore potassium secretion is impaired. This can result from any cause of marked volume depletion with enhanced proximal tubule reabsorption of sodium or from inhibition of distal sodium reabsorption with potassium-sparing diuretics, lithium, trimethoprim, sickle cell nephropathy, lupus nephritis, or urinary obstruction.