Gout

Definition/diagnostic criteria Gout is a form of inflammatory arthritis characterised by recurrent attacks of a red, tender, hot, and swollen joint, often the base of the big toe. It occurs due to hyperuricaemia – an excess of uric acid in the blood, leading to the deposition of monosodium urate crystals in joints and tissues. ‘Proof’ of diagnosis is achieved through the identification of monosodium urate crystals in synovial fluid or tophus, but this is only rarely necessary – the diagnosis can be made based on clinical criteria in the presence of hyperuricemia and characteristic acute arthritis.

Epidemiology Gout is the most common form of inflammatory arthritis in men over the age of 40, with a prevalence that increases with age. In the UK, the prevalence is approximately 2.5% among the general population. It’s more common in men than women and is often associated with other medical conditions like hypertension, diabetes, and chronic kidney disease, and with triggering factors such as diet and alcohol intake.

Diagnosis

Clinical features Gout typically presents with sudden onset of intense pain, swelling, and redness in the affected joint, most often the first metatarsophalangeal joint (big toe). Other joints, such as ankles, knees, elbows, wrists, and fingers, can also be affected. The acute episodes are called ‘gout attacks’ and may be triggered by dietary factors, dehydration, or other illnesses. Chronic tophaceous gout can develop in untreated cases, characterized by chronic arthritis and tophi (deposits of urate crystals).

Investigations Diagnostic investigations include serum uric acid level, which is often elevated during attacks but may be normal. Synovial fluid analysis from the affected joint shows negatively birefringent, needle-shaped monosodium urate crystals under polarized light microscopy. X-rays may not be useful in early disease but can show joint damage and tophi in chronic cases. Ultrasound and dual-energy CT (DECT) can also detect urate deposits, with DECT being particularly specific for gout.

Treatment The treatment of gout involves managing acute attacks and long-term management to reduce urate levels. For acute attacks, nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, or corticosteroids are used. Lifestyle modifications, including dietary changes and alcohol reduction, are also advised. For long-term management, urate-lowering therapy (ULT) such as allopurinol or febuxostat is recommended to maintain serum urate levels below the target range. Regular monitoring of serum urate levels, renal function, and liver enzymes (for febuxostat) is necessary during treatment.

Prognosis With proper treatment and adherence to lifestyle modifications, most individuals with gout can control their symptoms and prevent future attacks. Long-term complications include chronic arthropathy, joint damage, and the development of tophi. Comorbidities such as cardiovascular disease and renal impairment are also more common in individuals with gout, affecting overall prognosis. Early and effective treatment along with management of associated comorbidities improves the long-term outlook.