Hyperphosphataemia

1) Decreased urinary excretion

• Renal failure – Increased retention with reduced GFR
• Hypoparathyroidism (PTH essential to renal excretion)
  • Primary and Secondary
• Hyperthyroidism
  • Increased renal retention and bone resorption

2) Increased exogenous load

• When load exceeds renal capacity to excrete
• Increased risk in renal failure, bowel mucosal ulceration, ileus
• Laxatives, enemas

3) Increased endogenous load

• Tumour lysis syndrome
• Rhabdomyolysis
• Severe haemolysis
• Bowel infarction
• Malignant hyperthermia
• Bisphosphonates used in calcium treatment

Clinical manifestations

• Associated with hypocalcaemia and volume contraction
• Precipitates calcium out in serum
• Reduces calcitriol production
• Decreases calcium absorption form GI tract
• Tetany and paraesthesia (Compounds HYPOcalcaemia)

Correction

Dependant on duration and cause

1. Acute
   • Volume expansion if no renal failure
   • Dialysis if renal failure or tumour lysis syndrome
   • Insulin and dextrose (Transcellular)
     • Shifts phosphate from extracellular to intracellular
2. Chronic
   • Phosphate binding agents
   • Protein diet reduction