Gout on X-rays of a left foot: The typical location is the big toe joint. Note also the soft tissue swelling at the lateral border of the foot.
Spiked rods of uric acid crystals from a synovial fluid sample photographed under a microscope with polarized light. Formation of uric acid crystals in the joints is associated with gout.
Gout may be diagnosed and treated without further investigations in someone with hyperuricemia and the classic podagra. Synovial fluid analysis should be done, however, if the diagnosis is in doubt. X-rays, while useful for identifying chronic gout, have little utility in acute attacks.
Synovial fluid
A definitive diagnosis of gout is based upon the identification of monosodium urate crystals in synovial fluid or a tophus. All synovial fluid samples obtained from undiagnosed inflamed joints should be examined for these crystals. Under polarized light microscopy, they have a needle-like morphology and strong negative birefringence. This test is difficult to perform, and often requires a trained observer. The fluid must also be examined relatively quickly after aspiration, as temperature and pH affect their solubility.
Blood tests
Hyperuricemia is a classic feature of gout, but it occurs nearly half of the time without hyperuricemia, and most people with raised uric acid levels never develop gout. Thus, the diagnostic utility of measuring uric acid level is limited. Hyperuricemia is defined as a plasma urate level greater than 420 μmol/l (7.0 mg/dl) in males and 360 μmol/l (6.0 mg/dl) in females. Other blood tests commonly performed are white blood cell count, electrolytes, renal function, and erythrocyte sedimentation rate (ESR). However, both the white blood cells and ESR may be elevated due to gout in the absence of infection. A white blood cell count as high as 40.0×109/l (40,000/mm3) has been documented.
Differential diagnosis
The most important differential diagnosis in gout is septic arthritis. This should be considered in those with signs of infection or those who do not improve with treatment. To help with diagnosis, a synovial fluid Gram stain and culture may be performed. Other conditions that look similar include pseudogout and rheumatoid arthritis. Gouty tophi, in particular when not located in a joint, can be mistaken for basal cell carcinoma, or other neoplasms.
Treatment
The initial aim of treatment is to settle the symptoms of an acute attack. Repeated attacks can be prevented by different drugs used to reduce the serum uric acid levels. Ice applied for 20 to 30 minutes several times a day decreases pain. Options for acute treatment include nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine and steroids, while options for prevention include allopurinol, Deuric and probenecid. Lowering uric acid levels can cure the disease. Treatment of comorbidities is also important.
NSAIDs
NSAIDs are the usual first-line treatment for gout, and no specific agent is significantly more or less effective than any other. Improvement may be seen within four hours, and treatment is recommended for one to two weeks. They are not recommended, however, in those with certain other health problems, such as gastrointestinal bleeding, renal failure, or heart failure. While indomethacin has historically been the most commonly used NSAID, an alternative, such as ibuprofen, may be preferred due to its better side effect profile in the absence of superior effectiveness. For those at risk of gastric side effects from NSAIDs, an additional proton pump inhibitor may be given.
Colchicine
Colchicine is an alternative for those unable to tolerate NSAIDs. Its side effects (primarily gastrointestinal upset) limit its usage. Gastrointestinal upset, however, depends on the dose, and the risk can be decreased by using smaller yet still effective doses. Colchicine may interact with other commonly prescribed drugs, such as atorvastatin and erythromycin, among others.
Steroids
Glucocorticoids have been found as effective as NSAIDs and may be used if contraindications exist for NSAIDs. They also lead to improvement when injected into the joint; a joint infection must be excluded, however, as steroids worsens this condition.
Pegloticase
Pegloticase (Krystexxa) was approved in the USA to treat gout in 2010. It is an option for the 3% of people who are intolerant to other medications. Pegloticase is administered as an intravenous infusion every two weeks, and has been found to reduce uric acid levels in this population.
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