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What Is Uric Acid?
Gout can affect the ankles, heels and toes.
Credit: Alice Day | shutterstock

A byproduct of the body's metabolism, uric acid is a human waste product that most people never think about.

But for some people, uric acid can cause painful medical problems such as gout and kidney stones.

To understand what can go wrong with uric acid, you first need to know where this chemical comes from — purines. The purines that break down to form uric acid are nitrogen-containing compounds found in the cells of all plants and animals, including humans.

Purines are manufactured within the human body (endogenous purines) and are obtained from certain foods (exogenous purines) such as meats, seafood and alcoholic beverages.

Most healthy individuals are equipped to deal with a constant influx of purines. These chemicals pass through the liver (where they're broken down into uric acid), enter the bloodstream and then travel through the kidneys to be excreted from the body in the urine.

Some uric acid also goes through the intestines, where bacteria help break it down.

But in certain people, the purine processing cycle is off-kilter. Either these people's bodies produce too much uric acid, or their kidneys can't keep up with the removal of uric acid from the bloodstream. The resulting condition is known as hyperuricemia, or too much uric acid in the blood.

Some people with hyperuricemia are never treated for their condition, as they don't experience any symptoms. However, in some individuals, hyperuricemia leads to other painful conditions, such as gout.

Gout is a condition that develops when concentrations of uric acid in the blood get so high (about 7 milligrams per deciliter and above) that the acid starts to solidify, forming needlelike salt crystals (monosodium urate). These crystals, which tend to build up in certain areas — the joints, the skin near the joints, the outer ear and the kidneys — cause inflammation, pain and other symptoms.

Hyperuricemia can also lead to other conditions, like kidney stones (uric acid nephrolithiasis) and kidney failure. Kidney failure, however, is not often caused only by hyperuricemia — it usually develops in individuals who are also receiving chemotherapy treatment for certain types of cancers or corticosteroid therapy for severe allergic reactions.

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