Disorders Of Phosphate Hyperphosphatemia Flashcards
What is hyperphosphatemia defined as?
Serum [Pi] > 4.5 mg/dL
What is the term for a spurious increase in serum [Pi]?
Pseudohyperphosphatemia
In which conditions has pseudohyperphosphatemia been described?
- Hyperglobulinemia
- Hypertriglyceridemia
- Hyperbilirubinemia
What causes the spurious increase in serum phosphate levels?
Interference of proteins and triglycerides in the colorimetric assay of phosphate
What are the three major categories of true hyperphosphatemia causes?
- Addition of phosphate from ICF to ECF compartment
- Decrease in kidney excretion of phosphate
- Drugs
What are the most significant causes of hyperphosphatemia in clinical practice?
Acute and chronic kidney diseases
What is one endogenous cause of phosphate addition to the ECF compartment?
Hemolysis
What is a cause of phosphate addition to the ECF compartment that is exogenous?
Oral intake or through IV route
What condition involves the release of phosphate from muscle cells?
Rhabdomyolysis
What syndrome involves the release of phosphate from tumor cells due to chemotherapy?
Tumor lysis syndrome
Fill in the blank: Chronic kidney disease G4 and G5 leads to decreased kidney excretion of _______.
phosphate
What is the effect of excess vitamin D on phosphate levels?
Increased gastrointestinal absorption of phosphate
What is the mechanism of action for bisphosphonates regarding phosphate?
Decreased phosphate excretion, cellular shift
True or False: Diabetic ketoacidosis causes a shift of phosphate from ICF to ECF.
True
What genetic mutations are associated with familial tumor calcinosis?
- GALNT3
- FGF-23
- KLOTHO
What can lead to phosphate absorption from enemas?
Phosphate-containing enemas (Fleet enema)
What are immune checkpoint inhibitors associated with in terms of phosphate levels?
Tumor lysis syndrome (release from tumor cells)
What serum phosphate levels are common in patients with Acute Kidney Injury (AKI)?
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.
List the mechanisms for hyperphosphatemia in Acute Kidney Injury (AKI).
- Decreased kidney excretion
- Release from injured muscle
- Movement of phosphate out of cells during acute metabolic acidosis
What happens to phosphate homeostasis in early stages of Chronic Kidney Disease (CKD)?
It is maintained by progressive increase in phosphate excretion by surviving nephrons
This results in an increase of ( ext{FE}_{ ext{PO4}} ) > 35 %.
What role does FGF-23 play in phosphate excretion in early CKD?
It inhibits 1,25(OH)$_2$D$_3$ production, stimulating PTH secretion which increases phosphate excretion.
What is the GFR in CKD stages G4 and G5?
Less than 30 mL/min
How does Klotho deficiency contribute to hyperphosphatemia in CKD G4 and G5?
It causes resistance to FGF-23 action on phosphate excretion, leading to decreased phosphate excretion.
What is the result of the cycle involving Klotho deficiency and FGF-23 in CKD?
Hyperphosphatemia
What are the electrolyte abnormalities commonly observed with oral sodium phosphate (OSP) use?
- Hyperphosphatemia
- Hypocalcemia
- Hyponatremia
- Hypokalemia
- Hypernatremia
What is Familial Tumor Calcinosis (FTC)?
A rare autosomal recessive disorder characterized by hyperphosphatemia and deposition of calcium phosphate crystals.
What mutations are associated with Familial Tumor Calcinosis (FTC)?
- GALNT3
- FGF-23
- KLOTHO
What are the normal serum levels in patients with Familial Tumor Calcinosis (FTC)?
- Serum Ca(^{2+})
- PTH
- Alkaline phosphatase
What is Tumor Lysis Syndrome (TLS)?
An oncologic emergency that occurs following chemotherapy or spontaneously due to heavy tumor burden.
What are the important electrolyte disturbances in Tumor Lysis Syndrome (TLS)?
- Hyperkalemia
- Hyperphosphatemia
- Hyperuricemia
- Hypocalcemia
What are the symptoms of Tumor Lysis Syndrome (TLS)?
- Nausea
- Vomiting
- Poor appetite
- Dark and reduced urine output
- Seizures
- Palpitations
What is the treatment for Tumor Lysis Syndrome (TLS)?
- Volume replacement with normal saline
- Uricosuric drugs (e.g., allopurinol, febuxostat, rasburicase)
- Kidney replacement therapies if necessary
True or False: Rhabdomyolysis behaves similarly to Tumor Lysis Syndrome (TLS).
True
Except for the presence of myoglobinuria due to muscle necrosis in rhabdomyolysis.
What is the goal for maintaining phosphate levels in hyperphosphatemia treatment according to KDIGO?
PO₄ 3.5-5.5 mg/dL
KDIGO stands for Kidney Disease: Improving Global Outcomes, which provides guidelines for kidney disease management.
What are the key strategies for managing hyperphosphatemia?
- Dietary restriction
- Phosphate binders
- Dialysis optimization
- Treat underlying cause
What should be avoided in the dietary management of hyperphosphatemia?
- Processed foods (additive phosphates)
- Dairy products
- Nuts/legumes
- Colas (phosphoric acid)
What types of proteins are recommended for dietary management in hyperphosphatemia?
Plant-based proteins (lower bioavailability)
What are examples of calcium-based phosphate binders?
- Ca carbonate
- Ca acetate
What are the pros and cons of calcium-based phosphate binders?
- Pros: Low cost
- Cons: ↑ Vascular calcification, hypercalcemia
What is a key advantage of Sevelamer as a non-calcium based phosphate binder?
↓ LDL and ↓ vascular calcification
What are the cons of using Sevelamer?
GI side effects, expensive
What is the benefit of using Iron-based phosphate binders?
↑ Iron stores (benefit in anemia)
Which phosphate binder is limited by diarrhea?
Magnesium carbonate
What is the purpose of conventional hemodialysis in managing hyperphosphatemia?
Removes 700-900 mg/session
What is a limitation of conventional hemodialysis?
Limited by rebound from tissue stores
What are some enhanced removal techniques for dialysis?
- Nocturnal HD
- Daily HD
- Increased session duration
What is a treatment for acute hyperphosphatemia when PO₄ >10 mg/dL?
Emergent dialysis
What should be combined with binders in CKD-MBD treatment?
- Vitamin D analogs
- Calcimimetics (cinacalcet)
What parameters should be monitored monthly in dialysis patients?
- Serum PO₄
- Ca²⁺
- PTH
What is the target Ca×PO₄ product in hyperphosphatemia management?
<55 mg²/dL²
What mnemonic can help remember key points about phosphate binders?
BINDERS
What does the ‘B’ in the mnemonic ‘BINDERS’ stand for?
Balance Ca-PO₄
What does the ‘C’ in the mnemonic ‘CLASH’ stand for regarding binder types?
Calcium-based
What is the first-line treatment for hyperphosphatemia?
Dietary restriction + non-Ca binder
In which scenario should calcium-based binders be avoided?
If vascular calcification present
What is a clinical pearl regarding ferric citrate?
Ideal for patients with iron deficiency
What investigational agent may reduce binder pill burden in the future?
Tenapanor
What is crucial for phosphate control in hyperphosphatemia?
Dialysis adequacy
