What are uric acid stones?

Uric acid stones are one of four major types of kidney stones, which include calcium stones (calcium oxalate and calcium phosphate), struvite stones, and cystine stones. A kidney stone is a hard mass of crystallized minerals that form in the kidneys or urinary tract.

How common are uric acid stones?

It is estimated that one in 10 people in the U.S. will have a kidney stone of one kind or another at some time in their lives. In the late 1970s, about 3.8% of the population had kidney stones, but this figure has now increased to about 8.8% of the population. Among men, the lifetime risk is about 19%; in women, it is 9%. Usually, the first incidence of kidney stones occurs after age 30. However, there are many cases that occur sooner, some in children as young as five years of age.

What causes uric acid stones?

Uric acid stones form when the levels of uric acid in the urine is too high, and/or the urine is too acidic (pH level below 5.5) on a regular basis. High acidity in urine is linked to the following causes:

  • Inherited problems in how the body processes uric acid or protein in the diet can increase the acid in urine. This can be seen in conditions such as gout, which is known for its high levels of uric acid in the blood and painful deposits of crystals in the joints.
  • Uric acid can result from a diet high in purines, which are found especially in animal proteins such as beef, poultry, pork, eggs, and fish. The highest levels of purines are found in organ meats, such as liver and fish. Eating large amounts of animal proteins can cause uric acid to build up in the urine. The uric acid can settle and form a stone by itself or in combination with calcium. It is important to note that a person’s diet alone is not the cause of uric acid stones. Other people might eat the same diet and not have any problems because they are not prone to developing uric acid stones.
  • There is an increased risk of uric acid stones in those who are obese or diabetic.
  • Patients on chemotherapy are prone to developing uric acid stones.

What are the symptoms of uric acid stones?

All types of kidney stones produce similar symptoms, including one or more of the following:

  • Pain in the lower back, sides, abdomen or groin; the pain is the result of irritation or blockage inside the kidneys or urinary system
  • Blood in the urine
  • Nausea or vomiting
  • Fever and chills
  • Urine that smells bad or is cloudy during a urinary tract infection

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