Ca, PO4, Mg & Stones

Question 1

A patient with elevated PTH, high sCa, and very low urine Ca:Crea ratio (< 0.01), most likely has?

Answer 1

Familial hypocalciuric hypercalcemia (FHH)

Question 2

which of the ff can be caused by topiramate?
1. stones
2. AIN
3. drug induced vasculitis

Answer 2

stones.
topiramate is a CAI & can cause pRTA & dRTA, leading to stone formation

Question 3

does an alkalemic pH increase or decrease iCa?

Answer 3

decrease iCa

Question 4

how does omperazole (PPIs) result in hypomagnesemia?

Answer 4

PPIs decreases GI absorption og Mg by inhibiting TRPM6 chain. Renal Mg can. below.

Question 5

which should be replaced first when both K & Mg are low?

Answer 5

replace Magnesium first. low Magnesium can cause K wasting

Question 6

What is the genetic defect in Familial hypocalciuric hypercalcemia?

Answer 6

a heterozygous inactivating mutation of the CASR gene

Question 7

What type of Magnesium supplement can cause less diarrhea? Mg sulfate or Mg lactate?

Answer 7

Mg lactate

Question 8

at what level of urine oxalate threshold triggers further workup for primary hyperoxaluria?

Answer 8

urine oxalate > 75 mg/d

Question 9

first line treatment for uric acid stones?

Answer 9

Potassium citrate to alkalinize the urine.

Allopurinol is reserved for refractory stones

Question 10

Should you avoid giving K citrate in Calcium phosphate stones?

Answer 10

No need to avoid. No increased risk for calcium phosphate stone formation while on K-citrate.

Question 11

alternative medical therapy option for patients with struvite stones who are not surgical candidates?

Answer 11

Acetohydroxamic acid (urease inhibitor)

Question 12

Name 4 causes of hereditary forms of kidney stone disease?

Answer 12

Primary hyperoxaluria; Cystinuria; APRT deficiency; Dent disease

Question 13

Management of cystinuria?

Answer 13

1. give K-Citrate
2. increase urine volume, reduce salt & protein
3. give cystine-binding thiols (e.g. tiopronin)

Question 14

what is the mutation in Dent disease?

Answer 14

mutation of CLCN5

Question 15

alkali therapy will increase or decrease ammoniagenesis?

Answer 15

decrease ammoniagenesis

Question 16

how to estimate fluid intake needed to prevent cystine stone formation in patients with cystinosis?

Answer 16

divide 24 hour urine cystine by 250

Question 17

Atazanavir is soluble in acidic or alkaline urine pH?

Answer 17

Acidic pH

Question 18

Causes of pseudohyperphosphatemia? (4)

Answer 18

1. Heparin & alteplase
2. Amphotericin B
3. Paraproteinemia
4. Hyperlipidemia

Question 19

3 functions of FGF-23

Answer 19

1. Promotes phosphaturia by inhibiting NaPi-2a and NaPi-2c
2. Reduces calcitriol
3. Inhibits PTH
   Net effect of FGF-23: hypophosphatemia

Question 20

Acute respiratory alkalosis causes (high or low) serum phosphate?

Answer 20

Low serum phosphate.
Increased extracellular CO2 diffusion leads to a rise in intracellular pH, which increases glycolysis (needs ATP), which leads to increased intracellular phosphate uptake

Question 21

Acute metabolic alkalosis causes (high, low, or no effect) on serum phosphate

Answer 21

No effect.
Bicarbonate cannot freely cross the membranes to cause an increase in intracellular pH

Question 22

Chronic respiratory alkalosis causes (high, low) serum phosphate

Answer 22

High serum phosphate.
Due to renal resistance to PTH

Question 23

At what serum phosphate level do you start seeing symptoms related to hypophosphatemia?

Answer 23

Serum Phosphate < 1.5 to 2.0 mg/dL

Question 24

Calculate phosphate deficit

Answer 24

Phosphate deficit = 0.5 x kg body weight x (1.25 - serum PO4)

Question 25

Give 3 examples of vitamin D receptor agonists? (VDRA)

Answer 25

1. Calcitriol 2. Paricalcitol 3. Doxercalciferol

Question 26

Give 2 examples of calcimimetics or CaSR agonists?

Answer 26

Cinacalcet & etecalcitide

Question 27

Use of doxicalciferol may not be optimally effective in (heart failure, liver failure or CKD) patients

Answer 27

Liver failure. Doxicalciferol needs to be hydroxylated at the 24 position in the liver

Question 28

Prior to starting any Vitamin D supplementation, Serum phosphate levels should be ____?

Answer 28

Serum phosphate < 5.5 mg/dL Because vitamin D supplementation may worsen hyperphosphatemia

Question 29

What is the MOA of etecalcitide?

Answer 29

It is a direct CaSR agonist?

Question 30

What is the MOA of cinacalcet?

Answer 30

It changes the conformation of CaSR to better sense sCa

Question 31

Urinary Mg > 20 mg/d indicates what?

Answer 31

Renal Mg wasting

Question 32

Urinary Mg of < 10 mg/d indicates what?

Answer 32

Total body Mg depletion

Question 33

One 10 ml ampule of calcium gluconate contains how much grams of elemental calcium?

Answer 33

90 mg of elemental calcium

Question 34

One 10mL ampule of calcium gluconate contains how much grams of elemental calcium?

Answer 34

272 mg

Question 35

What is the stone size cutoff for medical expulsion therapy?

Answer 35

< 10 mm

Question 36

what medications can be used for medical stone expulsion therapy?

Answer 36

1. Alpha blockers: e.g. tamsulosin 2. CCB, nifedipine only 3. Steroids eg prednisone 20 mg x 10 days

Question 37

6 indications for urgent urology stone consults?

Answer 37

1. Infection with urinary tract obstruction 2. Urosepsis 3. Intractable pain or vomiting 4. Acute kidney failure 5. Obstruction in solitary or transplanted kidney 6. Bilateral obstructing stone

Question 38

What level of FePO4 is associated with renal phosphate wasting?

Answer 38

FePO4 > 5-20%