Gout and Hyperuricaemia
Gout is mainly associated with hyperuricaemia, although in some circumstances, gout may present in people with low uric acid level. In a condition where uric acid is high, plasma and extra cellular fluid will become supersaturated with uric acid, which may crystallize and result in clinical gout.
Causes:
- Hyperuricaemia – primary cause
- Polycythaemia
- Leukaemia
- Cytotoxics drugs
- Renal failure
- It may be precipitate by trauma, surgery, starvation, infections and diuretics
Pathophysiology:
- Hyperuricaemia (high uric acid level)
- Deposition of monosodium urate (MSU) crystals in joint – cause acute gouty arthritis
- MSU crystals are phagocytosed by leukocytes
- Release of inflammatory mediators and lysosomal enzymes leads to recruitment of additional phagocytes into the joint and to synovial inflammation
Clinical manifestations:
- Acute inflammatory arthritis - severe pain, redness and swelling of the affected joint (monoarthritis, but may be polyarticular) accompanied by fever
- Podagra (attack in the great toe) – it is the site of fist acute gouty arthritis in 50% of cases however, 90% of cases will eventually have the attack on the great toe.
- Chronic tophaceous arthritis (Tophi or deposition of urate) – this will present after repeated attacks of acute gouty arthritis
- Extraarticular tophi – often occur in olecranon bursa, helix and anthelix of ears, ulnar surface of forearm and Achilles tendon
- Tenosynovitis
- Urate nephrosis – deposition of MSU crystals in interstitium and pyramids of kidney (can cause chronic renal insufficiency)
- Acute uric acid nephropathy – reversible cause of acute renal failure due to precipitation of urate in tubules
- Uric acid nephrolithiasis – cause 10% of renal stones in the United States
Examination and investigations:
- Synovial fluid analysis – this is the only definitive method of diagnosing gouty arthritis. Joint aspiration will demonstrate needle shaped negatively birefringent MSU crystals by polarizing microscopy. Gram stain and culture should be done to rule out ongoing infection.
- Serum uric acid – normal level do not rule out gout
- Urine uric acid – excretion of >800mg/d on regular diet
- Screening for risk factors or sequelae – urinalysis; serum creatinine, glucose , lipids, full blood count
- If overproduction is suspected, measurement of erythrocyte hypoxanthine guanine phosphoribosyl transferase (HGPRT) and PRPP levels may be indicated
- Joint x rays – may demonstrate erosions late in disease
- If renal stones suspected , do abdominal flat plate (stone often radiolucent)
- Chemical analysis of renal stones
Treatment:
Asymptomatic hyperuricaemia - not indicated unless patient is plan for cytotoxic therapy for neoplasm.
Acute gouty arthritis - This attack is self limited, so treatment mainly to relieve the symptoms. Toxicity of therapy should be considered in each patient
- Analgesia
- NSAIDs – the treatment of choice if no contraindication
- Colchicine – effective on first 24 hours of attack.
- Intraarticular glucocorticoids – septic arthritis should be ruled out preceding to injection
- Systemic glucocorticoids
Uric acid lowering agents:
This type of drugs should not be started during an acute attack because it can precipitate an acute flare. Oral colchicines should be given then discontinue after uric acid become <5.0 mg/dL.
- Allopurinol - decrease uric acid synthesis by inhibiting xanthine oxidase. Dose should be reduced in renal insufficiency.
- Uricosuric drugs (probenicid, sulfinpyrazone) – increases uric acid excretion and ineffective in renal insufficiency.
Indication for uric acid lowering agents:
- Recurrent frequent acute gouty arthritis
- Polyarticular gouty arthritis
- Tophaceous gout
- Renal stones
- Cytotoxic therapy prophylaxis
DO you want to know more about gout? Know how to prevent the attacks… What are the foods that rich with purine that should be avoided? Please read my other article – “Tips: prevent acute gouty arthritis”
Reference:
- Oxford handbook of clinical specialties. 5th edition. 2001.
- Harrison’s Manual of Medicine. 16th edition. 2005.
Tags: acute gouty arthritis, allopuriol, gout, health, hyperuricaemia, investigations, monoarthritis, monosodium urate, podagra, probenicid, sulfinpyrazone, tenosynovitis, tophaceousarthritis, treatment, urate nephrosis
October 2nd, 2008 at 11:00 pm
IM a UK MD, with an interest in Rheumatology.
You may be aware of the newer gout drugs that are coming to market which are given by an injection once every 2 weeks. They are likely to revolutionise difficult to treat gout.
Its called Febuxostat in the UK- google it.