What is Gout?
Gout is a common cause of inflammatory arthritis cause by crystals forming in the joint. This results in recurring attacks of intense swelling, heat and redness of an affected joint. Flares of gout usually come on suddenly and within 24 hours can build into a very severe pain. A typical attack of gout will usually settle over 7 to 10 days, and in between attacks symptoms usually resolve completely.
Gout can affect any joint in the body, and can affect many joints at the same time, however most commonly it will affect a single joint at a time, usually the base of the big toe.
Gout is more common in men than in women, and it becomes more common with increasing age. Gout currently affects about 1 in 40 of the general population in the United Kingdom, however in men over the age of 70 this increases to about 1 in 10 of the population.
Causes of Gout
Gout is caused by crystals of urate that form in the joints. The crystals can rub against the joint lining (synovium) causing inflammation.
Urate is a normal break down product of purines. Purines are present in our cells and certain foods. Urate circulates in the blood and is usually passed harmlessly in the urine. However if the kidneys cannot get rid of the excess, or the body produces too much, levels in the body become raised (hyperuricaemia) and crystals can form within the joints, or under the skin.
High uric acid levels can be caused by kidney problems, drug treatments (particularly water tablets for high blood pressure or heart failure), as well increasing body weight and diet.
Symptoms of Gout
- Intense swelling, redness, and heat in the affected joint.
- Sudden onset with pain building in intensity over a number of hours
- Left untreated the attack will usually settle over a period of 7 to 10 days
- The most commonly affected joints are the toes, feet and ankles, however other joints can be involved
- In severe gout, crystals build up and form solid lumps of uric acid under the skin.
- They can appear white and chalky if they are close to the skin.
- Tophi typically form in cooler parts of the body such as the fingers and toes, overlying the elbows and knees, or even in the ear.
- Tophi are a marker of severe disease, but with sustained lowering of uric acid levels they will shrink and eventually disappear.
How do we diagnose Gout?
Diagnosis is made based on the history of presentation and examination. The typical presentation of recurrent attacks of pain, redness and swelling in the big toe of a middle aged man is classical.
- If the diagnosis is not obvious, the best test is to take a sample of the fluid in the swollen joint and look for crystals under a microscope. However this may not always be possible in smaller joints.
Blood urate levels:
- High levels would be expected in order for crystals to form
- However levels can frequently fall during an attack of gout, resulting in falsely negative levels
- The best time to measure uric acid is at least 4 to 6 weeks after the attack has resolved which gives a better idea of usual uric acid levels.
- Conversely most people with high levels of uric acid never go on to have attacks of gout, so that by itself this blood test does not establish a diagnosis of gout.
There are two key parts to the treatment of gout. Immediate and longer term treatment.
- Targets the pain and inflammation of an attack itself. These are best taken as quickly as possible when the flare starts
- Steroids- either targeted injection into a large joint, or a short course of tablets
- Aims to clear the crystals of uric acid from the body, and so prevent flares from happening again by lowering the blood urate levels
- Urate-lowering therapy (ULT)
- A number of therapies are available:
- Uricosuric drugs
- Diet and exercise
- Reduced intake of purine rich foods such as oily fish and shellfish; red meat and offal; alcohol (in particular beer) and full sugar soft drinks
- Increase water intake to prevent kidney stones
- Stopping certain drugs
- Some heart medications may be changed to another group that have some effect at lowering urate levels.
In newly diagnosed individuals, or patients with severe tophaceous disease the target blood urate level is 0.3mmol/l or lower. Therefore medications can be gradually increased to reach this target. In severe tophi, it can take months to years to clear the crystal build up.
Versus Arthritis: http://www.versusarthritis.org
UK Gout society: http://www.ukgoutsociety.org