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Residency Exam > Phosphate Disorders (Panopto Video File) > Flashcards

Phosphate Disorders (Panopto Video File) Flashcards

1
Q

What is the major anion within cells?

A

Phosphorus

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2
Q

What is the total amount of phosphorus in the average adult body?

A

850 g

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3
Q

What is the total amount of phosphorus in the average adult body?

A

850 g

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4
Q

What is the primary site of phosphorus in the body?

A

The bone (80 to 85%)

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5
Q

What percentage of total body phosphorus is in skeletal muscles?

A

10%

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6
Q

What percentage of total body phosphorus is in soft tissue cells besides skeletal muscles?

A

5%

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7
Q

What percentage of the body’s phosphorus is in the extracellular fluid?

A

1%

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8
Q

What form does the majority of intracellular phosphorus take?

A

Most intracellular phosphorus is in the organic form as a component of lipids, carbohydrates and proteins

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9
Q

What is the primary form phosphorus takes within bone?

A

It is a component of mineral hydroxyapatite

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10
Q

Describe the forms phosphorus takes in soft tissues

A

It is a structural element, as part of phospholipids in membranes, but is also a component of genetic material as part of RNA and DNA

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11
Q

How is phosphorus homeostasis maintained?

A

By balancing intestinal absorption and renal excretion

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12
Q

How is dietary phosphate which is not absorbed cleared?

A

In the faeces

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13
Q

Describe the reabsorption of phosphate from the kidneys

A

Phosphate is primarily reabsorbed from the proximal tubule, but also in part from the distal tubule

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14
Q

What is the usual amount of phosphate loss in the urine?

A

25 to 30 mmol per day

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15
Q

What 2 hormones is urinary loss of phosphate controlled by?

A

Parathyroid hormone and calcitriol

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16
Q

What is the usual amount of phosphate loss in the faeces?

A

15 mmol per day

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17
Q

What are 3 activities of fibroblast growth factor-23 on phosphate?

A
  1. Increased urinary excretion of phosphate
  2. Reduced renal production of calcitriol
  3. Decreased parathyroid hormone secretion
18
Q

What is a factor which may inhibit the effects of fibroblast growth factor-23 on phosphate?

A

Renal impairment

19
Q

What is the concern for phosphate overload in patients with renal impairment?

A

Deposition of phosphorus in the vascular organs

20
Q

What are 5 expected non-classical effects of fibroblast growth factor-23?

A
  1. Increased cardiac hypertrophy/cardiac fibrosis (heart failure)
  2. Increased cytokine production
  3. Reduced immune response
  4. Reduction in red blood cells (erythrocytes)
  5. Reduction in bone mineralisation
21
Q

Describe the effects of hyperphosphataemia on the cardiovascular system

A

Hyperphosphataemia is associated with increased cardiovascular risk

22
Q

Describe the clinical effects of hyperphosphataemia

A

Clinical effects include those of hypocalcaemia (tetany, seizures, ectopic calcification)

23
Q

What are 3 methods of treatment of hyperphosphataemia?

A
  1. Haemodialysis
  2. Phosphate binders
  3. Glucose (shifts phosphate intracellularly)
24
Q

Describe the usual prognosis of hyperphosphataemia

A

If renal function is normal and hydration is maintained, hyperphosphataemia is usually transient

25
Q

If tetany occurs secondary to hyperphosphataemia, what may be needed?

A

Treatment with intravenous calcium

26
Q

Excessive administration of intravenous calcium in the presence of high phosphate concentrations can cause deposition of calcium phosphate salts and lead to what 3 complications?

A
  1. Acute kidney injury
  2. Blood vessel damage
  3. Lung damage
27
Q

What must you differentiate between when a patient presents with low phosphate?

A
  1. Hypophosphataemic syndrome (i.e. phosphate redistribution)
  2. True hypophosphataemia
28
Q

What are the two pillars of treatment for hypophosphataemia?

A

Intravenous supplements and oral supplements

29
Q

What are 2 common causes of true hypophosphataemia?

A
  1. Trauma (or other tissue/end organ damage)
  2. Refeeding syndromes
30
Q

What are 3 aetiologies of hypophosphataemia?

A
  1. Decreased intake
  2. Redistribution from blood to cells
  3. Increased excretion from the kidneys
31
Q

What is a common cause of increased phosphate excretion from the kidneys?

A

Polyuria secondary to acute recovery from an acute kidney injury

32
Q

Describe the interpretability of phosphorus

A

The rapid shifts of phosphorus between the extracellular fluid and intracellular fluid frequently compound the assessment of total body phosphorus

33
Q

What are 5 causes of decreased phosphate intake?

A
  1. Insufficiency concentrated total parenteral nutrition
  2. Malabsorption in small intestine (Crohn’s, coeliac), including malabsorption or Vitamin D
  3. Magnesium or aluminium-based antacids
  4. Starvation
  5. Inadequate dietary intake
34
Q

Why may magnesium and aluminium-based antacids cause hypophosphataemia?

A

As they form insoluble complexes in the intestine

35
Q

Describe the effects of alkalosis on phosphate

A

Alkalosis causes phosphate to move intracellularly to produce ATP

36
Q

What are 6 causes of hypophosphataemia?

A
  1. Respiratory alkalosis
  2. Recovery from malnutrition
  3. Recovery from diabetic ketoacidosis
  4. Hormal agents
  5. Sepsis
  6. Hungry bone syndrome
37
Q

Why may recovery from malnutrition lead to hypophosphataemia?

A

As the body drives the phosphate into cells

38
Q

What are 6 hormones which may cause hypophosphataemia?

A
  1. Insulin
  2. Glucagon
  3. Cortisol
  4. Glucose
  5. Fructose
  6. Lactate
39
Q

How does a parathyroidectomy acutely affect electrolytes?

A

Calcium and phosphate tend to drop significantly

40
Q

Describe the usual presentation of hypophosphataemia

A

It is usually asymptomatic

41
Q

What are 9 signs/symptoms of chronic, severe hypophosphataemia?

A
  1. Anorexia
  2. Muscle weakness
  3. Osteomalacia
  4. Rhabdomyolysis
  5. Haemolytic anaemia
  6. Impaired leukocyte function
  7. Impaired platelet function
  8. Encephalopathy
  9. Coma
42
Q

What are 9 signs/symptoms of chronic, severe hypophosphataemia?

A
  1. Anorexia
  2. Muscle weakness
  3. Osteomalacia
  4. Rhabdomyolysis
  5. Haemolytic anaemia
  6. Impaired leukocyte function
  7. Impaired platelet function
  8. Encephalopathy
  9. Coma

Residency Exam (22 decks)

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