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Nelson - Nephrology > RTA > Flashcards

Flashcards in RTA Deck (61):
1

Blood pH in RTA

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

2

Types of RTA

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

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RTA that results from impaired bicarbonate reabsorption

Proximal

4

RTA that results from failure to secrete acid

Distal

5

Approximately 90% of filtered bicarbonate is reabsrobed in the

Proximal tubule

6

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

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

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Drugs that can cause secondary pRTA

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

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Nutritional condition that can cause pRTA

Kwashiorkor

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Isolated autosomal recessive pRTA is caused by mutations in

Gene encoding the sodium bicarbonate transporter NBC1

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Cystinosis is suggested by what clinical finding

Cystine crystals in the cornea

11

Cystinosis is confirmed by measurement of

Increased leukocyte cystine content

12

Specific therapy for Cystinosis is available with cysteamine which acts to

Bind to cystine and convert it to cysteine

13

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

T

14

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

Lowe syndrome

15

In Lowe syndrome, kidneys show

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

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

Cystinosis

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

Lowe syndrome

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

Growth failure

19

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

Patients with Fanconi syndrome have additional symptoms secondary to phosphate wasting

20

Urinalysis in patients with isolated pRTA shows

Generally unremarkable except for an acidic urine pH <5.5

21

Urinary indices in patients with Fanconi syndrome

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

22

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

Less than 5.5

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Why is there hyperchloremia in distal RTA

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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Why is there hypokalemia in distal RTA

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

25

Bone disease is common in distal RTA because

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

26

Distal RTA is distinguished from pRTA by the presence of

1) Nephrocalcinosis 2) Hypercalciuria

27

pRTA is distinguished from dRTA by the presence of

Phosphate and massive bicarbonate wasting

28

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

Medullary sponge kidney

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Inability to concentrate urine

Hyposthenuria

30

Type IV RTA occurs as the result of

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

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Mechanism for acidosis in Type IV RTA

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

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Mechanism for hyperkalemia in Type IV RTA

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

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

Aldosterone unresponsiveness

34

Absence of aldosterone leads to what basic pattern of electrolyte imbalance

Elevated urinary sodium with inappropriately low urinary K

35

First step in the evaluation of a patient with suspected RTA

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

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

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

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

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

NAGMA with normal or low K suggests what types of RTA

I or II

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Formula for anion gap

Na - (Cl+HCO3)

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NAGMA is demonstrated by an anion gap of

Less than 12

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HAGMA is demonstarted by an anion gap of

>20

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Steps in evaluation of possible RTA

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

Urine anion gap in distal RTA

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

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Urine anion gap in pRTA

(-) gap is consistent with proximal tubule bicarbonate wasting

45

Mainstay of therapy in all forms of RTA

Bicarbonate replacement

46

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

pRTA

47

Large quantities of bicarbonate is defined as

20mEq/kg/24hr

48

Base requirement for distal RTAs is generally in the range of

2-4mEqs/kg/24hr

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Syndrome manifesting with RTA that usually requires phosphate supplementation

Fanconi syndrome

50

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

Distal RTA

51

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

Thiazide diuretics to decrease urine Ca excretion

52

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

Na-K exchange resin (Kayexalate)

53

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

T, provided serum bicarbonate is maintained within normal levels

54

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

pRTA

55

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

Type I or distal RTA

56

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

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

57

Bone demineralization in distal RTA probably relates to

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

Management for rickets in patients with distal RTA

Bicarbonate supplement

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Management for rickets in patients with pRTA

Both bicarbonate and oral phosphate supplements

60

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

Vitamin D

61

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

Bone demineralization + Vitamin D deficiency