Gout

Overview

Gout is a type of arthritis caused by the deposition of monosodium urate crystals in and around joints (crystal arthropathy) causing sudden flares of severe pain, heat, and swelling. It is associated with hyperuricaemia, however, people without hyperuricaemia can develop gout, and some people with hyperuricaemia may never go on to develop gout.

Over time, large crystals can deposit in different regions of the body leading to irregular nodules known as gouty tophi and chronic joint damage.

Epidemiology

• Gout is the most common inflammatory arthritis
• More common in men (particularly those aged >30 years old) and postmenopausal women

Risk Factors

• Obesity
• Drugs – thiazides and loop diuretics, low-dose salicylates except those used in cardiovascular prophylaxis, chemotherapy
• Hypertension, coronary heart disease and heart failure
• Diabetes mellitus
• Chronic kidney disease
• High triglycerides
• Psoriasis
• Menopause
• Meat and seafood consumption
• Alcohol consumption

Presentation

Gout typically presents acutely (over hours) or sometimes overnight with redness and swelling in a joint. Features include:

• Acute severe joint pain, swelling, and warmth– may occur overnight
  • Typical joints affected are in the feet, most cases occur in the first metatarsophalangeal joint (MTP) of the foot
  • Usually monoarticular or oligoarticular (<5 joints)
    • It may be polyarticular in older people
• Gouty tophi may be present – these suggest longstanding, untreated gout
  • They are seen on extensor surfaces of affected joints, Achilles tendons, dorsal hands and feet, and the helix of the ear
• Some patients may gave chronic inflammatory joint pain – chronic gouty arthritis

Signs on examination

• Joints are warm, red, and swollen
• Tender joints
• Limited range of movement due to pain
• Tophi may be seen on the extensor surfaces of the elbows, knees, Achilles tendons, or dorsal aspects of the hands and feet, and in the helix of the ears

Differential Diagnoses

Septic arthritis

• This may present identically to gout
• Septic arthritis should be considered in those with features of infection or systemic upset (with or without fever), or those who do not improve with treatment
• If suspected, refer the patient for emergency joint aspiration and culture
• There may be risk factors for septic arthritis including prior joint replacement, pre-existing joint damage, a recent intra-articular injection, intravenous drug use, or immunosuppression 

Pseudogout

• This may present identically to gout
• Pseudogout tends to affect the wrist and knee joints
• Joint aspiration and analysis help differentiate gout and pseudogout

Rheumatoid arthritis (RA)

• Gouty tophi may appear similar to rheumatoid nodules
• Intermittent episodes of arthritis suggest gout, particularly if it affects the feet
• RA tends to present with a bilateral symmetrical polyarthritis affecting small bones in the hands and feet

Psoriatic arthritis (PsA)

• There may be a history of psoriasis
• PsA may have dactylitis
• PsA may have nail changes (e.g. pitting or onycholysis)
• Skin nodules are not seen in PsA

Reactive arthritis

• There may be a history of a sexually-transmitted infection or gastroenteritis
• Reactive arthritis tends to affect larger joints in the lower limb
• Other features of reactive arthritis may be present including urethritis and conjunctivitis

Investigations

• Arthrocentesis with synovial fluid analysis is diagnostic:
  • Strongly negatively birefringent needle-shaped crystals under polarised light
• Uric acid around 2 weeks after the attack resolves:
  • This is because it may be falsely low or normal during attacks

Investigations to consider are

• Ultrasound scan which may show:
  • Erosions
  • Tophi
  • Double contour lines
• X-ray which may show:
  • Periarticular erosions (may have a punched-out appearance or an overhanging edge)

Management

Acute flare

In an acute flare, prescribe one of the following, depending on comorbidities: 

• 1^st line: NSAIDs (e.g. naproxen/ibuprofen/diclofenac/celecoxib)
  • Avoid if contraindicated e.g. renal impairment/GI bleeds
• Or 1^st line: colchicine
  • Common side effects are: diarrhoea, nausea, and vomiting
  • Avoid if eGFR <10mL/minute/1.73m²
• Or 1^st line: prednisolone intra-articular or parenterally depending on the severity
  • Used if NSAIDs and colchicine are contraindicated
  • Should be avoided if septic arthritis hasn’t been excluded
• If the patient is already taking allopurinol, this should be continued

Chronic management

Urate-lowering therapy (ULT) is now offered to all patients after their first attack of gout. ULT should be offered around 2 weeks after an attack as the British Society of Rheumatologists recommend that it is better for patients to decide to take long-term ULT while not in pain.

• 1^st line: allopurinol + suppressive therapy (“cover” therapy)
  • Suppressive therapy options are: colchicine, naproxen, ibuprofen, diclofenac
  • If NSAIDs and colchicine are contraindicated, prednisolone may be considered
• 2^nd line: febuxostat if allopurinol is not tolerated/ineffective + suppressive therapy

Monitoring

• When starting allopurinol, closely monitor patients for hypersensitivity
  • This may manifest as multi-system failure, eosinophilia, and dermatitis
• Monitor patients for recurrent attacks, the development of tophi, and radiographic changes
• If patients are on urate-lowering therapy, follow up uric acid levels every 1-3 months initially then every 6-12 months
• Monitor for adverse effects of NSAIDs, colchicine, and allopurinol, especially if used for prolonged periods. Obtain FBC, U&Es, and LFTs every 3-6 months
• A medication review is essential as allopurinol has multiple drug interactions
  • Azathioprine should never be prescribed with allopurinol as it can cause fatal haematological toxicity

Patient Advice

Patients should have lifestyle changes:

• Drinking alcohol responsibly
• Avoiding dehydration
• Reduction in the quantity of purine-based food consumption e.g. herring/sardines/liver/kidneys/oatmeal
• Reducing meat or seafood intake
• Weight reduction
• Regular exercise
• Smoking cessation

Risk factors should also be optimised.

Complications

• Chronic arthritis and joint damage
• Uric acid renal stones
• Gouty tophi
• Hyperuricaemia is associated with an increased risk of cardiovascular disease and chronic kidney disease

Prognosis

• Acute attacks usually resolve over 5-15 days
• The risk of recurrence in those not taking urate-lowering therapy (ULT) is around 62% in the first year and 84% in the third year
• Early treatment with ULT can reduce the risk of future attacks and long-term complications