Gout

Gout is an inflammatory arthritis caused by monosodium urate crystals in and around joints. 

The most commonly affected joint is the first metatarsophalangeal joint. When this is affected it is called a podagra

Tophi may develop in chronic disease.

The most important risk factor for developing gout is hyperuricaemia

Hyperuricaemia may be caused by: 
  • Urate overproduction: 
    • Psoriasis
    • Excessive dietary purine intake 
    • Cytotoxics 
    • B12 
    • Alcohol 
  • Urate underexecretion 
    • Renal impairment 
    • Diuretics 
    • Low-dose aspirin (but not this should still be given for cardioprotection if indicated) 
    • Hypothyroidism 
    • Lead poisoning 

Investigation
  • Microscopy of joint aspirate - monosodium urate crystals are fine, needlelike and negatively birefringent under polarized light. 
  • Serum urate level – usually raised but may be normal during an acute attack
  • XR 
    • Usually normal until chronic disease and then may show extra-articular erosions and widened joint space 

Management 
  • Acute gout 
    • Rest joint 
    • NSAIDs 
    • Colchicine if NSAIDs contraindicated 
    • Corticosteroids (orally or intraarticularly) if NSAIDs/colchicine not sufficient 
    • Do not start allopurinol during an acute attack 
  • Preventative options 
    • Diet inclusive of soy beans, cherries and skimmed milk
    • Avoidance of liver, kidneys, shellfish and yeast extracts/purine rich foods
    • Restrict alcohol intake 
    • Allopurinol 
      • Works by inhibiting xanthine oxidase 
      • Give if 
        • Second attack or 
        • Tophi or 
        • Renal insufficiency or 
        • Uric acid stones or 
        • On diuretics 
      • Start 1-2 weeks after inflammation has settled 


Small print gem: a side effect of colchicine is diarrhoea 


References 

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