Gout is a type of crystal arthropathy associated with chronically high blood uric acid levels. Urate crystals are deposited in the joint causing it to become hot, swollen and painful.
Gouty tophi are subcutaneous deposits of uric acid typically affecting the small joints and connective tissues of the hands, elbows and ears. The DIP joints are most affected in the hands.
It typically presents with a single acute hot, swollen and painful joint. The obvious and extremely important differential diagnosis is septic arthritis.
- High purine diet (e.g. meat and seafood)
- Existing cardiovascular or kidney disease
- Family history
- Base of the big toe (metatarsophalangeal joint)
- Base of thumb (carpometacarpal joints)
Gout can also affects large joints like the knee and ankle.
Gout is diagnosed clinically or by aspiration of fluid from the joint. Excluding septic arthritis is essential as this is a potential joint and life-threatening diagnosis.
Aspirated fluid will show:
- No bacterial growth
- Needle shaped crystals
- Negatively birefringent of polarised light
- Monosodium urate crystals
- Typically the space between the joint is maintained
- Lytic lesions in the bone
- Punched out erosions
- Erosions can have sclerotic borders with overhanging edges
During the acute flare:
- NSAIDs (e.g. ibuprofen) are first-line
- Colchicine second-line
- Steroids can be considered third-line
Colchicine is used in patients that are inappropriate for NSAIDs, such as those with renal impairment or significant heart disease. A notable side effect is gastrointestinal upset. Diarrhoea is a very common side effect. This is dose-dependent meaning lower doses cause less upset than higher doses.
Allopurinol is a xanthine oxidase inhibitor used for the prophylaxis of gout. It reduces the uric acid level.
Lifestyle changes can reduce the risk of developing gout. This involves losing weight, staying hydrated and minimising the consumption of alcohol and purine-based food (such as meat and seafood).
TOM TIP: Do not initiate allopurinol prophylaxis until after the acute attack is settled. Once treatment of allopurinol has been started then it can be continued during an acute attack.
Last updated July 2020