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Nelson - Nephrology > RTA > Flashcards

RTA Flashcards

1
Q

Blood pH in RTA

A

NAGMA (hyperchloremic) in the setting of near normal or normal GFR

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2
Q

Types of RTA

A

Proximal (Type II), Distal (Type I), Combined proximal and distal (Type III), Hyperkalemic (Type IV)

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3
Q

RTA that results from impaired bicarbonate reabsorption

A

Proximal

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4
Q

RTA that results from failure to secrete acid

A

Distal

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5
Q

Approximately 90% of filtered bicarbonate is reabsrobed in the

A

Proximal tubule

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6
Q

Proximal RTA usually occurs as a component of global proximal tubular dysfunction or Fanconi syndrome, which is characterized by

A

1) LMW proteinuria 2) Glycosuria 3) Phosphaturia 4) Amino aciduria 5) Proximal RTA

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7
Q

Drugs that can cause secondary pRTA

A

1) Gentamicin 2) Cisplatin 3) Ifosfamide 4) Sodium valproate

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8
Q

Nutritional condition that can cause pRTA

A

Kwashiorkor

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9
Q

Isolated autosomal recessive pRTA is caused by mutations in

A

Gene encoding the sodium bicarbonate transporter NBC1

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10
Q

Cystinosis is suggested by what clinical finding

A

Cystine crystals in the cornea

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11
Q

Cystinosis is confirmed by measurement of

A

Increased leukocyte cystine content

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12
Q

Specific therapy for Cystinosis is available with cysteamine which acts to

A

Bind to cystine and convert it to cysteine

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13
Q

T/F Oral cysteamine as treatment for Cystinosis does not achieve adequate levels in ocular tissues, so additional therapy with cysteamine eyedrops is required.

A

T

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14
Q

A rare X-linked disorder characterized by congenital cataracts, mental retardation, and Fanconi syndrome

A

Lowe syndrome

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15
Q

In Lowe syndrome, kidneys show

A

Nonspecific tubulointerstitial changes; Thickening of glomerular basement membrane; And changes in proximal tubule mitochondria

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16
Q

Present in the 1st 2 yr of life with severe tubular dysfunction and growth failure

A

Cystinosis

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17
Q

Typically present in infancy with cataracts, progressive growth failure, hypotonia, and Fanconi syndrome

A

Lowe syndrome

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18
Q

Patients with isolated, sporadic, or inherited pRTA present with ____ in the 1st yr of life.

A

Growth failure

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19
Q

How does patients with primary Fanconi syndrome compare to those with isolated pRTA

A

Patients with Fanconi syndrome have additional symptoms secondary to phosphate wasting

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20
Q

Urinalysis in patients with isolated pRTA shows

A

Generally unremarkable except for an acidic urine pH <5.5

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21
Q

Urinary indices in patients with Fanconi syndrome

A

1) Phosphaturia 2) Aminoaciduria 3) Glycosuria 4) Uricosuria 5) Elevated urinary sodium or potassium

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22
Q

In distal RTA, urine pH cannot be reduced to ___ despite the presence of severe metabolic acidosis

A

Less than 5.5

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23
Q

Why is there hyperchloremia in distal RTA

A

Loss of sodium bicarbonate distally, owing to lack of H+ to bind to in the tubular lumen, results in increased chloride absorption (HCO3-Cl exchanger on the basolateral membrane)

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24
Q

Why is there hypokalemia in distal RTA

A

Inability to secrete H+ is compensated by increased K+ secretion distally

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25
Q

Bone disease is common in distal RTA because

A

There is mobilization of organic components from bone to serve as buffers to chronic acidosis

26
Q

Distal RTA is distinguished from pRTA by the presence of

A

1) Nephrocalcinosis 2) Hypercalciuria

27
Q

pRTA is distinguished from dRTA by the presence of

A

Phosphate and massive bicarbonate wasting

28
Q

Characterized by cystic dilation of the terminal portions of the collecting ducts as they enter the renal pyramids

A

Medullary sponge kidney

29
Q

Inability to concentrate urine

A

Hyposthenuria

30
Q

Type IV RTA occurs as the result of

A

Impaired aldosterone production (hypoaldosteronism) or impaired renal responsiveness to aldosterone (pseudohypoaldosteronism)

31
Q

Mechanism for acidosis in Type IV RTA

A

Aldosterone has a direct effect on the H+/ATPase responsible for hydrogen secretion; Hyperkalemia –> inhibition of ammoniagenesis and hence H excretion

32
Q

Mechanism for hyperkalemia in Type IV RTA

A

Aldosterone is a potent stimulant for K secretion in the collecting tubule

33
Q

More common cause of Type IV RTA: Adrenal gland disorder (e.g. Addison disease, CAH) vs Aldosterone unresponsiveness

A

Aldosterone unresponsiveness

34
Q

Absence of aldosterone leads to what basic pattern of electrolyte imbalance

A

Elevated urinary sodium with inappropriately low urinary K

35
Q

First step in the evaluation of a patient with suspected RTA

A

1) Confirm presence of NAGMA 2) Identify electrolyte abnormalities 3) Assess renal function 4) Rule out other causes of bicarbonate loss such as diarrhea

36
Q

Patients who have persistent metabolic acidosis despite correction of volume depletion likely has RTA

A

F, protracted diarrhea can deplete their total-body bicarbonate stores and can have persistent acidosis despite apparent restoration of volume status; where a patient has a recent history of severe diarrhea, full evaluation for RTA should be delayed for several days to permit adequate time for reconstitution of total-body bicarbonate stores

37
Q

Conditions that can lead to falsely low bicarbonate levels, often in association with an elevated serum K

A

1) Traumatic blood draws such as heel-stick specimens 2) Small volumes of blood in “adult-size” specimen collection tubes 3) Prolonged specimen transport time at room temp

38
Q

NAGMA with normal or low K suggests what types of RTA

A

I or II

39
Q

Formula for anion gap

A

Na - (Cl+HCO3)

40
Q

NAGMA is demonstrated by an anion gap of

A

Less than 12

41
Q

HAGMA is demonstarted by an anion gap of

A

> 20

42
Q

Steps in evaluation of possible RTA

A

1) First step as above 2) Urine pH to distinguish distal from proximal causses (less than 5.5 = pRTA, >6 = dRTA) 3) (Optional) Compute urine anion gap [(urine Na + urine K) - urine Cl 4) UA (glycosuria, proteinuria, hematuria) 5) Ca-Crea ratio 6) Renal UTZ

43
Q

Urine anion gap in distal RTA

A

(+) gap suggests a deficiency of ammoniagenesis and, thus, the possibility of dRTA

44
Q

Urine anion gap in pRTA

A

(-) gap is consistent with proximal tubule bicarbonate wasting

45
Q

Mainstay of therapy in all forms of RTA

A

Bicarbonate replacement

46
Q

Patients with this type of RTA often require large quantities of bicarbonate

A

pRTA

47
Q

Large quantities of bicarbonate is defined as

A

20mEq/kg/24hr

48
Q

Base requirement for distal RTAs is generally in the range of

A

2-4mEqs/kg/24hr

49
Q

Syndrome manifesting with RTA that usually requires phosphate supplementation

A

Fanconi syndrome

50
Q

Patients with this type of RTA should be monitored for development of hypercalciuria

A

Distal RTA

51
Q

Patients with symptomatic hypercalciuria (recurrent gross hematuria, nephrocalcinosis, or nephrolithiasis) can require what medication

A

Thiazide diuretics to decrease urine Ca excretion

52
Q

Patients with type IV RTA can require chronic treatment for hyperkalemia with

A

Na-K exchange resin (Kayexalate)

53
Q

T/F Patients with treated isolated proximal or distal RTA can demonstrate improvement in growth

A

T, provided serum bicarbonate is maintained within normal levels

54
Q

Rickets may be present in primary RTA, particularly in what type of RTA

A

pRTA

55
Q

Bone demineralization without overt rickets usually is detected in what type of RTA

A

Type I or distal RTA

56
Q

T/F The circulating levels of 1,25(OH)2D in patients with either type of RTA are generally decreased

A

F, generally normal; decreased in cases where there is a concomitant CKD

57
Q

Bone demineralization in distal RTA probably relates to

A

Dissolution of bone because the calcium carbonate in bone serves as a buffer against the metabolic acidosis due to the hydrogen ions retained by patients with RTA

58
Q

Management for rickets in patients with distal RTA

A

Bicarbonate supplement

59
Q

Management for rickets in patients with pRTA

A

Both bicarbonate and oral phosphate supplements

60
Q

This is required to offset the secondary hyperparathyroidism that complicates oral phosphate therapy in patients with RTA

A

Vitamin D

61
Q

Patients with Type II RTA and primary Fanconi syndrome may present with “double osteomalacia” which is defined as

A

Bone demineralization + Vitamin D deficiency

Nelson - Nephrology (13 decks)

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