Hyperuricaemia

Definition

• Men >0.42 mmol/l

• Women >0.36 mmo/l - lower in premenopausal women

Causes

• Increased urate formation

• Decreased renal excretion

• Combinations

Renal urate excretion

• 100% filtered at the glomerulus

• 90% reabsorbed at the proximal tubule

• 50% back secreted back into the tubule

• 40% tubular reabsorption

• Net : 10% loss

Monosodium urate crystals

• Monosodium urate has low solubility

• needle shaped

• 2-10µm long

• negatively birefringent with polarised light

• deposited in

  • soft tissues

  • joints

  • urinary tract

Causes

Primary

Secondary

• increased urate formation

  • excessive dietary purines
    • red wine
    • red meat
  • disordered ATP metabolism
  • Alcohol excess
  • obesity
  • malignant disease
  • increased nucleic acid turnover
    • cytotoxic drugs
    • psoriasis
• decreased renal secretion
  • impaired renal function
  • thiazide diuretics
  • low dose aspirin
  • lead poisoning
  • organic acids
    • lactic - increased production during hypoxaemia
    • alcohol
    • toxaemia of pregnancy

Healthy populations

• men

• high socioeconomic groups

• obesity

• post-menopausal women

• 1st year of life

Clinical consequences

• Acute Gout

• Arthritis

• Urate nephropathy

• renal calculi

Differential diagnosis

• Septic arthritis

• Crystalline arthropathy

Features associated with hyperuricaemia

• Obesity

• Hypertension

• hypertriglyceridaemia

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