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Gout

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of gout.

Alternative Names

Hyperuricemia

Diagnosis

The first step in diagnosing the disease is to determine which joints are affected. A physical examination and medical history can help confirm or rule out gout. For example, gout is more likely if arthritis first appears in the big toe.

The speed of the onset of pain and swelling is also important. Symptoms that take days or weeks rather than hours to develop probably indicate a disorder other than gout.

Abnormal enlargements in joints that had been affected by previous injury or osteoarthritis are possible signs of gout. This is particularly significant in older women who take diuretics ("water pills").

Examination of Synovial Fluid

Synovial fluid examination is the most accurate method for diagnosing gout. The synovial fluid is the lubricating liquid that fills the synovium (the membrane that surrounds a joint and creates a protective sac). The fluid cushions joints and supplies nutrients and oxygen to cartilage, the slippery tissue that coats the ends of bones. This exam also helps detect gout during intercritical periods.

The health care provider uses a needle attached to a syringe to draw out fluid from the affected joint. This is called aspiration. Local anesthesia is not used because it can reduce the effectiveness of the procedure. However, the procedure is usually only mildly uncomfortable. Afterwards, there can be some minor discomfort in the area where the needle was inserted, but it usually goes away quickly.

The fluid sample is sent to a laboratory for analysis. Testing can reveal the presence of monosodium urate (MSU) crystals, which will nearly always confirm a diagnosis of gout. The laboratory can also test the sample for infection.

The procedure itself can cause infection, though this occurs in less than 0.1% of patients. Aspiration sometimes eases a patient’s symptoms by reducing swelling and pressure on the tissue surrounding the joint.

Blood Test for Uric Acid Levels

A blood test is usually given for measuring uric acid and detecting hyperuricemia. A low level of uric acid in the blood makes a diagnosis of gout much less probable, and a very high level increases the likelihood of gout. Some experts argue, however, that such measurements are not very useful, given that uric acid levels in the blood during an attack of gout can lie within or below the normal range, and the presence of hyperuricemia doesn't necessarily mean someone has gout. However, new research suggests that closer monitoring of blood uric acid levels in those with gout may help reduce gout flares as well as health care costs.

Urine Tests

It is sometimes helpful to gauge the amount of uric acid found in a patient's urine, particularly if the patient is young and has pronounced hyperuricemia that might be related to a metabolic disorder. If uric acid in the urine exceeds a particular value, further tests for an enzyme defect or other identifiable cause of gout should be performed. Greater-than-normal amounts of uric acid in the urine also mean that the patient is more likely to develop uric acid kidney stones.

Typically, a 24-hour urine test is performed. The patient discards the first urination sample on the day of the test. Afterward all urine passed over the next 24 hours is collected into a special container, including the first urination on the morning of day two. The container is delivered to the patient’s health care provider or sent directly to the laboratory.

The urine is collected during an intercritical period, after the patient has been placed on a purine-reduced diet. The patient is also asked to temporarily stop using alcohol and any medications that can interfere with the test. The patient should not change any of his or her usual eating or drinking patterns when performing this test.

Imaging Tests

X-Rays. For the most part, x-rays do not reveal any problems during the early stages of gout. Their usefulness lies in assessing the progress of the disorder in its chronic phase and identifying other health problems with symptoms similar to gout. Tophi can be seen on x-rays before they become apparent on physical examination.

Advanced Imaging Techniques. Advanced imaging techniques being investigated for identifying tophi include computed tomography (CT), magnetic resonance imaging (MRI), and Doppler ultrasonography. A 2002 study comparing these approaches found that CT scans offered the best images.

Ruling Out Other Disorders

As part of the diagnosis, other disorders that produce gout-like symptoms or cause hyperuricemia should be ruled out. In general, it is easy to distinguish acute gout that occurs in one joint from other arthritic conditions. The two disorders that may confuse this diagnosis are pseudogout and septic arthritis. Chronic gout can often resemble rheumatoid arthritis. Several other conditions may at some point in their course resemble gout. Pseudogout is a condition most likely to be confused with gout. See box: " Pseudogout (Calcic Gout) ."

Pseudogout (Calcic Gout) Pseudogout (also called calcic gout and calcium pyrophosphate dihydrate deposition disease) is a common inflammatory arthritis among older adults. It is very similar to gout, but is caused by deposits of calcium pyrophosphate dihydrate crystals in and around the joints. Although symptoms of pseudogout resemble gout in some ways, there are differences: The first attack typically strikes the knee. Other joints commonly affected are the shoulders, wrists, and ankles. At least two-thirds of cases affect more than one joint during a first attack. It may involve any joint, although the small joints in the fingers or toes are not commonly affected. The symptoms of pseudogout also appear more slowly than those of gout, taking days rather than hours to develop. Pseudogout is more likely to first develop in elderly people, particularly those with osteoarthritis. (It affects 10 - 15% of people over 65.) Pseudogout is more likely to occur in the autumn while gout attacks are most common in the spring. Who Gets Pseudogout? Conditions that are associated with a higher risk for pseudogout in elderly patients include underlying acute medical conditions, trauma, or surgery. Medical conditions associated with pseudogout include hypothyroidism, diabetes, gout, and osteoarthritis. Liver transplantation also may increase the risk. How Is Pseudogout Treated? There is no cure for pseudogout. It is a progressive disorder that can eventually destroy joints. Treatments for pseudogout are similar to those for gout and are aimed at relieving the pain and inflammation and reducing the frequency of attacks. NSAIDs are effective for treating inflammation and pain from pseudogout. For acute attacks in large joints, fluid aspiration alone or with corticosteroids may help. Colchicine may be used for acute attacks. Magnesium carbonate may help dissolve crystals but existing hard deposits may remain. Surgery may be required for joint replacement.

Rheumatoid Arthritis. Rheumatoid arthritis can distort the joints of the finger and cause inflammation and pain that may mimic gout. In older people, it is particularly difficult to distinguish chronic gout from rheumatoid arthritis. A proper diagnosis can be made with a detailed medical history, laboratory tests, and identification of MSU crystals.

Osteoarthritis. Gout can coincide and be confused with osteoarthritis in older people, particularly when it occurs in arthritic finger joints in women. In general, gout should be suspected if the joints in the fingertips are unusually enlarged.

Infections. Joint infections can have features that resemble gout. A correct diagnosis is critical for appropriate treatment. For example, some cases of gout have been confused with infection after joint replacement. On the other hand, joint infection not associated with surgery might indicate sepsis, which is a widespread and potentially life-threatening bacterial infection that can cause inflamed joints, chills, and a spiking fever. The severity of the fever and a high white blood cell count in the joint fluid helps diagnose a septic infection, while urate crystals in the joint are a good indicator of gout.

Charcot Foot. Between 1 - 2.5% of people with diabetes have Charcot foot or Charcot joint (medically referred to as neuropathic arthropathy). This condition is caused by problems in the nerves in the feet. Early changes may resemble gout, with the foot becoming swollen, red, and warm. Recognition and treatment of this condition is very important. A seriously affected foot can become deformed. The bones may crack, splinter, and erode, and the joints may shift, change shape, and become unstable.

Bunions. A bunion is a deformity that usually occurs at the head of the first of five long bones (the metatarsal bones) that extend from the arch and connect to the toes, and may be confused with gout. The first metatarsal bone is the one that attaches to the big toe. A bunion begins to form when the big toe is forced in toward the rest of the toes, causing the head of the first metatarsal bone to jut out and rub against the side of the shoe. The underlying tissue becomes inflamed, and a painful bump forms. As this bony growth develops, the bunion is formed as the big toe is forced to grow at an increasing angle towards the rest of the toes.

Some Diseases with Symptoms Similar to Gout
Disease	Specific Subtypes
Osteoarthritis
Infectious Arthritis	Lyme disease, septic arthritis, bacterial endocarditis, mycobacterial and fungal arthritis, viral arthritis, osteomyelitis
Postinfectious or Reactive Arthritis	Reiters syndrome (a disorder characterized by arthritis and inflammation in the eye and urinary tract), rheumatic fever, inflammatory bowel disease
Pseudogout
Rheumatic Autoimmune Diseases	Rheumatoid arthritis, systemic vasculitis, systemic lupus erythematosus, scleroderma, Still's disease (also called juvenile rheumatoid arthritis)
Fibromyalgia
Other Diseases	Chronic fatigue syndrome, hepatitis C, familial Mediterranean fever, cancers, AIDS, leukemia, bunions, Whipple's disease, dermatomyositis, Behcet's disease, Henoch-Schonlein purpura, Kawasaki's disease, erythema nodosum, erythema multiforme, pyoderma gangrenosum, pustular psoriasis

• Review Date: 11/30/2006
• Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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