Managing Gout In The Lower Extremity
Initial attacks of gout often affect the first metatarsophalangeal joint (MPJ). Accordingly, this author discusses the differential diagnosis of lower extremity gout, keys to managing acute attacks and how to get a handle on the disease’s metabolic causes. He also discusses current and emerging pharmaceutical options for treating the disease.
Gout is a metabolic condition characterized by excessive levels of serum urate. The consensus is that a serum urate level above 6.0 mg/dL, the saturation point of urate in biological fluids, is the cause of gout.
Elevated levels of serum urate over time lead to deposits of monosodium urate crystals within joints. Attacks of gout are due to the sudden release of these crystals into the joint, where they elicit an acute inflammatory response characterized by warmth, redness, swelling and excruciating pain.
The pain often starts at night or early in the morning. Patients will state that they awaken from foot pain so severe that they cannot “bear the weight of the sheet” on the foot. Walking is next to impossible. In addition to these symptoms, fatigue, malaise and a low-grade fever may be present.
Most gout attacks resolve, at least early on, within three to 14 days, even without treatment. However, with time, the attacks become more frequent, last longer and spread to involve other joints.
Ninety percent of first attacks affect one joint, usually the first metatarsophalangeal joint (MPJ). This condition is called podagra.
However, other types of arthritis such as calcium pyrophosphate arthropathy (CPPD), Reiter’s disease, septic arthritis and psoriatic arthritis can produce a similar clinical picture. The instep of the foot may also be a target for a first attack and patients may think they have “turned their ankle.”
When it comes to other conditions to consider in the differential diagnosis, we know that osteoarthritis may affect the first MPJ and possibly lead to a bunion. One may mistake this condition for gout. In cases in which septic arthritis is a possibility, joint aspiration is mandatory. Finally, cellulitis is another condition that can be confused with acute gout.
A Closer Look At The Criteria For Diagnosing Gout
When it comes to the classification of acute arthritis with primary gout, the American College of Rheumatology notes there are a variety of possible criteria.1 These criteria may include:
• more than one attack of acute arthritis
• maximum inflammation developing within a day
• monoarthritis attack
• redness over joints
• painful or swollen first MPJ
• unilateral first MPJ attack
• unilateral tarsal joint attack
• asymmetric swelling within a joint on radiography
• subcortical cysts without erosions on radiography
• monosodium urate crystals in joint fluid during an attack
• joint fluid culture negative for organisms during an attack
A diagnosis of gout is highly likely if:
• monosodium urate crystals are detected in joint fluid
• a tophus containing urate crystals is identified
• six or more of the aforementioned criteria are present.
Measurement of serum uric acid during an attack may be helpful. Although a highly elevated level of serum uric acid supports the diagnosis, a normal level does not exclude the diagnosis. Keep in mind that serum urate levels do tend to be elevated two weeks after an attack.
One study demonstrated that measuring serum urate during an attack and then measuring two weeks later yields two serum urate levels that one can compare to help with the diagnosis. The authors concluded that patients were unlikely to have gout if they had low serum urate levels (2