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Renal 2 > Renal Tubular Acidosis > Flashcards

Renal Tubular Acidosis Flashcards

1
Q

Bicarbonate

where is it filtered?

where is it reabsorbed?

by what channels?

A

Bicarbonate

  1. filtered by the glomerulus (bulk filtration)
  2. reabsorption
    1. 90% in Proximal Tubule
      1. Na-H exchange​
      2. Type II RTA
    2. 10% in distal nephron
      1. Hydrogen secretion via proton pump (H-ATPase)
      2. Type I RTA
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2
Q

What is the major mode of acid excretion in the body?

where does it occur?

what ion is it secreted with?

A

The major mode of acid excretion in the body is ammonium (NH4) in the collecting tubules

when ammonium is excreted it is secreted with chloride

it can also be excreted along with phosphate. When this is the case it is referred to as titratable acidity.

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3
Q

defects in distal hydrogen excretion are what type of RTA?

A

Type I

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4
Q

defects that reduce capacity to reclaim filtered bicarbonate in the proximal tubule is what type of RTA?

A

Type 2 (proximal)

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5
Q

Reductions in aldosterone secretion or responsiveness is what type of RTA?

A

Type 4 (hypoaldosteronism)

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6
Q

Potassium

  1. where does reabsorption take place?
  2. where does secretion take place?
  3. what stimulates secretion?
A

Potassium

  1. reabsorption of potassium takes place in the proximal tubule and the loop of henle. Almost 100% of potassium is reabsorbed.
  2. secretion is the primary mechanism for excretion. it takes place in the collecting duct
  3. secretion is stimulated by Aldosterone and the distal delivery of sodium and water to the collecting duct.
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7
Q

Type 1 RTA

  1. impaired ______
  2. what are the two mechanisms known that can cause this?
  3. Bicarbonate levels can fall to <_____. This type of acidosis is ______ severe than Type 2.
A

Type 1 RTA

  1. impaired hydrogen ion secretion in the distal nephron
  2. Two mechanism known:
    1. decreased activity of the proton pump (H-ATPase)
    2. increased luminal hydrogen ion permeability
  3. Bicarbonate levels can fall to <10meq/L. This type of acidosis is more severe than Type 2.

**The proton pump is the primary defense mechanism against acidosis because it secretes ammonium

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8
Q

What are some causes of type 1 RTA?

  1. Primary
  2. Secondary
    1. autoimmune
  3. Drugs

Which is most likely to occur in children?

A

Causes of type 1 RTA

  1. Primary
    1. idiopathic- most likely to occur in children
    2. familial
  2. Secondary
    1. autoimmune
      1. Sjogrens Syndrome
      2. SLE
  3. Drugs: Amphotericin B, Toluene
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9
Q

More causes of Type 1 RTA

  1. Secondary
    1. Nephrocalcinosis
  2. Other:
A

More causes of Type 1 RTA

  1. Secondary
    1. Nephrocalcinosis
      1. hyperparathyroidism, sarcoidosis, Vit D intoxication, idiopathic hypercalcuria
  2. Other: Medullary sponge kidney
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10
Q

Type 2 RTA

  1. this is a decrease in the proximal _______ reabsorptive capacity
  2. What are some common drugs that can cause this?
  3. what is the serum bicarbonate level?
  4. why is this type of RTA less severe than type 1?
A

Type 2 RTA

  1. this is a decrease in the proximal bicarbonate reabsorptive capacity
  2. Carbonic anhydrase inhibitors can cause type 2 RTA
  3. The serum bicarbonate level is 14-20 meq/L
  4. This type of RTA is less severe because the distal nephron can reabsorb some of the bicarbonate that has escaped
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11
Q

What syndrome is type 2 RTA associated with?

What are some associated factors with this syndrome?

A

Fanconi Syndrome- a general proximal tubular dysfunction (decreased reabsorption in general)

glucosuria

phosphaturia

uricosuria

aminoaciduria

tubular proteinuria

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12
Q

What levels of potassium excretion do we expect in type 2 RTA?

  1. in the absence of alkali?
  2. if alkali is administered?
A

potassium levels vary in type 2 RTA depending on the administration of alkali

  1. in the absence of alkali the plasma bicarb falls until filtered bicarb is reduced to a level that permits reabsorption (Na/K transport is normal)
  2. if alkali is administered, filtered bicarb level increases to a level that exceeds reabsorptive capacity. This increaes the distal delivery of Na, bicarb, and water which increases K secretion leading to hypokalemia
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13
Q

what is the kidney’s role in maintaining acid base balance?

A

H+ ions are added to ammonia creating ammonium in the kidney, this is the main way that the body excretes acid.

the kidney also controls the secretion of bicarb

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14
Q

Should you give alkali treatment to a patient with type 2 RTA?

A

NO.

the filtered bicarb exceeds the body’s capacity for reabsorption. This increases the distal delivery of Na and water to the distal nephron which stimulates secretion of potassium. This can eventually lead to hypokalemia

**Give Potassium along with any alkali

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15
Q

Type 4 RTA

  1. a problem with _______
  2. this leads to a ______ rate of proton secretion in the distal tubule
  3. what is the serum bicarbonate level?
  4. what is the major contributor to metabolic acidosis?
A

Type 4 RTA

  1. a problem with aldosterone synthesis or the action of aldosterone in the kidney
  2. this leads to a reduced rate of proton secretion in the distal tubule
  3. The serum bicarbonate level is usually >15 meq/L
  4. Hyperkalemia is the major contributor to the metabolic acidosis. Increased levels of potassium inhibit ammoniagenesis and reduces urinary ammonium excretion
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16
Q

How do you correct the acidosis in type 4 RTA?

A

you can correct the acidosis by correcting the potassium handling in the kidney

17
Q

Complications of RTA

type 1, type 2, or type 4

  1. Demineralization of bones
  2. Nephrolithiasis/Nephrocalcinosis
  3. Hypokalemia
  4. Hyperkalemia
A

Complications of RTA

type 1, type 2, or type 4

  1. Demineralization of bones- Type 2
  2. Nephrolithiasis/Nephrocalcinosis- Type 1
  3. Hypokalemia- Type 1 and type 2
  4. Hyperkalemia type 4
18
Q

Treatment

  1. Type 1
  2. Type 2
  3. Type 4
A

Treatment

  1. Type 1 (distal)- oral alkali suppliments and potassium supplements
  2. Type 2- (made worse with oral alkali suppliments but you still treat with them. so you give potassium along with the treatment. Treat children more agressibely
  3. Type 4: lower the serum K (thiazide or loop diuretic)
19
Q

What is a normal anion gap?

A

a normal anion gap is 12

a normal anion gap occurs when the decrease in bicarb is matched by an equal increase in Cl (hyperchloremic metabolic acidosis)

an increased AG happens when an unmeasured anion is added

20
Q
A
21
Q

how do we correct the AG for hypoalbuminemia?

A

2.5 x [albumin] = expected AG

22
Q

when do we calculate a urine anion gap?

what is the sign of an inappropriate renal response?

A

when a person has metabolic acidosis with a normal anion gap

it is an indirect measurement of urinary ammonium excretion

a positove UAG in teh setting of metabolic acidosis is a sign of an inappropriate renal response

23
Q

Type 1:

  1. Seurm Bicarb:
  2. effect on serum K
  3. effect on urine pH
A

Type 1:

  1. Seurm Bicarb: <10
  2. effect on serum K: hypokalemia that will correct with alkali
  3. effect on urine pH: >5.3
24
Q

Type 2:

  1. Defect:
  2. Seurm Bicarb:
  3. effect on serum K
  4. effect on urine pH
A

Type 2:

  1. Defect: reduced proximal bicarb reabsorption
  2. Seurm Bicarb: 12-20 mEq/L
  3. effect on serum K: hypokalemia that is made worse with alkali
  4. effect on urine pH: variable.
    1. >5.3 if serum bicarb exceeds reabsorptive threshold
    2. <5.3 if bicarb is reduced to a level that can be largely reabsorbed
25
Q

Type 4:

  1. Defect:
  2. Serum bicarb:
  3. urine pH:
  4. plasma K:
A

Type 4:

  1. Defect: decreased aldosterone secretion or aldosterone resistance
  2. Serum bicarb: >17 mEq/L
  3. urine pH: <5.3
  4. plasma K: hyperkalemia
26
Q

Causes of Type 4 RTA:

  1. decreased aldosterone production:
  2. Aldosterone resistance:
A

Causes of Type 4 RTA:

  1. decreased aldosterone production:
    1. renal disease
    2. NSAIDs
  2. Aldosterone resistance:
    1. ENaC inhibitors
      1. K sparing diuretics (eplerenone, spironolactone)
      2. antibiotics (trimethoprim)

Renal 2 (18 decks)

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