Disorders Of Phosphate Hyperphosphatemia

Question 1

What is hyperphosphatemia defined as?

Answer 1

Serum [Pi] > 4.5 mg/dL

Question 2

What is the term for a spurious increase in serum [Pi]?

Answer 2

Pseudohyperphosphatemia

Question 3

In which conditions has pseudohyperphosphatemia been described?

Answer 3

• Hyperglobulinemia
• Hypertriglyceridemia
• Hyperbilirubinemia

Question 4

What causes the spurious increase in serum phosphate levels?

Answer 4

Interference of proteins and triglycerides in the colorimetric assay of phosphate

Question 5

What are the three major categories of true hyperphosphatemia causes?

Answer 5

• Addition of phosphate from ICF to ECF compartment
• Decrease in kidney excretion of phosphate
• Drugs

Question 6

What are the most significant causes of hyperphosphatemia in clinical practice?

Answer 6

Acute and chronic kidney diseases

Question 7

What is one endogenous cause of phosphate addition to the ECF compartment?

Answer 7

Hemolysis

Question 8

What is a cause of phosphate addition to the ECF compartment that is exogenous?

Answer 8

Oral intake or through IV route

Question 9

What condition involves the release of phosphate from muscle cells?

Answer 9

Rhabdomyolysis

Question 10

What syndrome involves the release of phosphate from tumor cells due to chemotherapy?

Answer 10

Tumor lysis syndrome

Question 11

Fill in the blank: Chronic kidney disease G4 and G5 leads to decreased kidney excretion of _______.

Answer 11

phosphate

Question 12

What is the effect of excess vitamin D on phosphate levels?

Answer 12

Increased gastrointestinal absorption of phosphate

Question 13

What is the mechanism of action for bisphosphonates regarding phosphate?

Answer 13

Decreased phosphate excretion, cellular shift

Question 14

True or False: Diabetic ketoacidosis causes a shift of phosphate from ICF to ECF.

Answer 14

True

Question 15

What genetic mutations are associated with familial tumor calcinosis?

Answer 15

• GALNT3
• FGF-23
• KLOTHO

Question 16

What can lead to phosphate absorption from enemas?

Answer 16

Phosphate-containing enemas (Fleet enema)

Question 17

What are immune checkpoint inhibitors associated with in terms of phosphate levels?

Answer 17

Tumor lysis syndrome (release from tumor cells)

Question 18

What serum phosphate levels are common in patients with Acute Kidney Injury (AKI)?

Answer 18

Between 5 and 10 mg/dL

In cases of AKI caused by rhabdomyolysis, tumor lysis syndrome, hemolysis, or severe burns, levels may reach as high as 20 mg/dL.

Question 19

List the mechanisms for hyperphosphatemia in Acute Kidney Injury (AKI).

Answer 19

• Decreased kidney excretion
• Release from injured muscle
• Movement of phosphate out of cells during acute metabolic acidosis

Question 20

What happens to phosphate homeostasis in early stages of Chronic Kidney Disease (CKD)?

Answer 20

It is maintained by progressive increase in phosphate excretion by surviving nephrons

This results in an increase of ( ext{FE}_{ ext{PO4}} ) > 35 %.

Question 21

What role does FGF-23 play in phosphate excretion in early CKD?

Answer 21

It inhibits 1,25(OH)$_2$D$_3$ production, stimulating PTH secretion which increases phosphate excretion.

Question 22

What is the GFR in CKD stages G4 and G5?

Answer 22

Less than 30 mL/min

Question 23

How does Klotho deficiency contribute to hyperphosphatemia in CKD G4 and G5?

Answer 23

It causes resistance to FGF-23 action on phosphate excretion, leading to decreased phosphate excretion.

Question 24

What is the result of the cycle involving Klotho deficiency and FGF-23 in CKD?

Answer 24

Hyperphosphatemia

Question 25

What are the electrolyte abnormalities commonly observed with oral sodium phosphate (OSP) use?

Answer 25

* Hyperphosphatemia * Hypocalcemia * Hyponatremia * Hypokalemia * Hypernatremia

Question 26

What is Familial Tumor Calcinosis (FTC)?

Answer 26

A rare autosomal recessive disorder characterized by hyperphosphatemia and deposition of calcium phosphate crystals.

Question 27

What mutations are associated with Familial Tumor Calcinosis (FTC)?

Answer 27

* GALNT3 * FGF-23 * KLOTHO

Question 28

What are the normal serum levels in patients with Familial Tumor Calcinosis (FTC)?

Answer 28

* Serum Ca(^{2+}) * PTH * Alkaline phosphatase

Question 29

What is Tumor Lysis Syndrome (TLS)?

Answer 29

An oncologic emergency that occurs following chemotherapy or spontaneously due to heavy tumor burden.

Question 30

What are the important electrolyte disturbances in Tumor Lysis Syndrome (TLS)?

Answer 30

* Hyperkalemia * Hyperphosphatemia * Hyperuricemia * Hypocalcemia

Question 31

What are the symptoms of Tumor Lysis Syndrome (TLS)?

Answer 31

* Nausea * Vomiting * Poor appetite * Dark and reduced urine output * Seizures * Palpitations

Question 32

What is the treatment for Tumor Lysis Syndrome (TLS)?

Answer 32

* Volume replacement with normal saline * Uricosuric drugs (e.g., allopurinol, febuxostat, rasburicase) * Kidney replacement therapies if necessary

Question 33

True or False: Rhabdomyolysis behaves similarly to Tumor Lysis Syndrome (TLS).

Answer 33

True ## Footnote Except for the presence of myoglobinuria due to muscle necrosis in rhabdomyolysis.

Question 34

What is the goal for maintaining phosphate levels in hyperphosphatemia treatment according to KDIGO?

Answer 34

PO₄ 3.5-5.5 mg/dL ## Footnote KDIGO stands for Kidney Disease: Improving Global Outcomes, which provides guidelines for kidney disease management.

Question 35

What are the key strategies for managing hyperphosphatemia?

Answer 35

* Dietary restriction * Phosphate binders * Dialysis optimization * Treat underlying cause

Question 36

What should be avoided in the dietary management of hyperphosphatemia?

Answer 36

* Processed foods (additive phosphates) * Dairy products * Nuts/legumes * Colas (phosphoric acid)

Question 37

What types of proteins are recommended for dietary management in hyperphosphatemia?

Answer 37

Plant-based proteins (lower bioavailability)

Question 38

What are examples of calcium-based phosphate binders?

Answer 38

* Ca carbonate * Ca acetate

Question 39

What are the pros and cons of calcium-based phosphate binders?

Answer 39

* Pros: Low cost * Cons: ↑ Vascular calcification, hypercalcemia

Question 40

What is a key advantage of Sevelamer as a non-calcium based phosphate binder?

Answer 40

↓ LDL and ↓ vascular calcification

Question 41

What are the cons of using Sevelamer?

Answer 41

GI side effects, expensive

Question 42

What is the benefit of using Iron-based phosphate binders?

Answer 42

↑ Iron stores (benefit in anemia)

Question 43

Which phosphate binder is limited by diarrhea?

Answer 43

Magnesium carbonate

Question 44

What is the purpose of conventional hemodialysis in managing hyperphosphatemia?

Answer 44

Removes 700-900 mg/session

Question 45

What is a limitation of conventional hemodialysis?

Answer 45

Limited by rebound from tissue stores

Question 46

What are some enhanced removal techniques for dialysis?

Answer 46

* Nocturnal HD * Daily HD * Increased session duration

Question 47

What is a treatment for acute hyperphosphatemia when PO₄ >10 mg/dL?

Answer 47

Emergent dialysis

Question 48

What should be combined with binders in CKD-MBD treatment?

Answer 48

* Vitamin D analogs * Calcimimetics (cinacalcet)

Question 49

What parameters should be monitored monthly in dialysis patients?

Answer 49

* Serum PO₄ * Ca²⁺ * PTH

Question 50

What is the target Ca×PO₄ product in hyperphosphatemia management?

Answer 50

<55 mg²/dL²

Question 51

What mnemonic can help remember key points about phosphate binders?

Answer 51

BINDERS

Question 52

What does the 'B' in the mnemonic 'BINDERS' stand for?

Answer 52

Balance Ca-PO₄

Question 53

What does the 'C' in the mnemonic 'CLASH' stand for regarding binder types?

Answer 53

Calcium-based

Question 54

What is the first-line treatment for hyperphosphatemia?

Answer 54

Dietary restriction + non-Ca binder

Question 55

In which scenario should calcium-based binders be avoided?

Answer 55

If vascular calcification present

Question 56

What is a clinical pearl regarding ferric citrate?

Answer 56

Ideal for patients with iron deficiency

Question 57

What investigational agent may reduce binder pill burden in the future?

Answer 57

Tenapanor

Question 58

What is crucial for phosphate control in hyperphosphatemia?

Answer 58

Dialysis adequacy