RTA

Question 1

Blood pH in RTA

Answer 1

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

Question 2

Types of RTA

Answer 2

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

Question 3

RTA that results from impaired bicarbonate reabsorption

Answer 3

Proximal

Question 4

RTA that results from failure to secrete acid

Answer 4

Distal

Question 5

Approximately 90% of filtered bicarbonate is reabsrobed in the

Answer 5

Proximal tubule

Question 6

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

Answer 6

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

Question 7

Drugs that can cause secondary pRTA

Answer 7

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

Question 8

Nutritional condition that can cause pRTA

Answer 8

Kwashiorkor

Question 9

Isolated autosomal recessive pRTA is caused by mutations in

Answer 9

Gene encoding the sodium bicarbonate transporter NBC1

Question 10

Cystinosis is suggested by what clinical finding

Answer 10

Cystine crystals in the cornea

Question 11

Cystinosis is confirmed by measurement of

Answer 11

Increased leukocyte cystine content

Question 12

Specific therapy for Cystinosis is available with cysteamine which acts to

Answer 12

Bind to cystine and convert it to cysteine

Question 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.

Answer 13

T

Question 14

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

Answer 14

Lowe syndrome

Question 15

In Lowe syndrome, kidneys show

Answer 15

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

Question 16

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

Answer 16

Cystinosis

Question 17

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

Answer 17

Lowe syndrome

Question 18

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

Answer 18

Growth failure

Question 19

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

Answer 19

Patients with Fanconi syndrome have additional symptoms secondary to phosphate wasting

Question 20

Urinalysis in patients with isolated pRTA shows

Answer 20

Generally unremarkable except for an acidic urine pH <5.5

Question 21

Urinary indices in patients with Fanconi syndrome

Answer 21

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

Question 22

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

Answer 22

Less than 5.5

Question 23

Why is there hyperchloremia in distal RTA

Answer 23

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)

Question 24

Why is there hypokalemia in distal RTA

Answer 24

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

Question 25

Bone disease is common in distal RTA because

Answer 25

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

Question 26

Distal RTA is distinguished from pRTA by the presence of

Answer 26

1) Nephrocalcinosis 2) Hypercalciuria

Question 27

pRTA is distinguished from dRTA by the presence of

Answer 27

Phosphate and massive bicarbonate wasting

Question 28

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

Answer 28

Medullary sponge kidney

Question 29

Inability to concentrate urine

Answer 29

Hyposthenuria

Question 30

Type IV RTA occurs as the result of

Answer 30

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

Question 31

Mechanism for acidosis in Type IV RTA

Answer 31

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

Question 32

Mechanism for hyperkalemia in Type IV RTA

Answer 32

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

Question 33

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

Answer 33

Aldosterone unresponsiveness

Question 34

Absence of aldosterone leads to what basic pattern of electrolyte imbalance

Answer 34

Elevated urinary sodium with inappropriately low urinary K

Question 35

First step in the evaluation of a patient with suspected RTA

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

NAGMA with normal or low K suggests what types of RTA

Answer 38

I or II

Question 39

Formula for anion gap

Answer 39

Na - (Cl+HCO3)

Question 40

NAGMA is demonstrated by an anion gap of

Answer 40

Less than 12

Question 41

HAGMA is demonstarted by an anion gap of

Answer 41

>20

Question 42

Steps in evaluation of possible RTA

Answer 42

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

Question 43

Urine anion gap in distal RTA

Answer 43

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

Question 44

Urine anion gap in pRTA

Answer 44

(-) gap is consistent with proximal tubule bicarbonate wasting

Question 45

Mainstay of therapy in all forms of RTA

Answer 45

Bicarbonate replacement

Question 46

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

Answer 46

pRTA

Question 47

Large quantities of bicarbonate is defined as

Answer 47

20mEq/kg/24hr

Question 48

Base requirement for distal RTAs is generally in the range of

Answer 48

2-4mEqs/kg/24hr

Question 49

Syndrome manifesting with RTA that usually requires phosphate supplementation

Answer 49

Fanconi syndrome

Question 50

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

Answer 50

Distal RTA

Question 51

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

Answer 51

Thiazide diuretics to decrease urine Ca excretion

Question 52

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

Answer 52

Na-K exchange resin (Kayexalate)

Question 53

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

Answer 53

T, provided serum bicarbonate is maintained within normal levels

Question 54

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

Answer 54

pRTA

Question 55

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

Answer 55

Type I or distal RTA

Question 56

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

Answer 56

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

Question 57

Bone demineralization in distal RTA probably relates to

Answer 57

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

Question 58

Management for rickets in patients with distal RTA

Answer 58

Bicarbonate supplement

Question 59

Management for rickets in patients with pRTA

Answer 59

Both bicarbonate and oral phosphate supplements

Question 60

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

Answer 60

Vitamin D

Question 61

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

Answer 61

Bone demineralization + Vitamin D deficiency