Uric Acid Stones
What are uric acid stones?
Uric acid stones are one of four types of kidney stones. A kidney stone is a collection of minerals and salt that hardens. Kidney stones form in the kidneys or urinary tract, the path that urine takes to leave the body. They can cause pain and blood in the urine, but treatment can help.
Other types of kidney stones include:
- Calcium stones.
- Struvite stones.
- Cystine stones.
What is uric acid?
Uric acid is a waste product that’s in your blood. Your body produces uric acid when it breaks down chemicals called purines. Most uric acid dissolves in your blood and passes through the kidneys. It leaves your body in your urine.
How do uric acid stones form?
If you have high levels of uric acid, then crystals start to form. These uric acid crystals combine with other substances in your body and create a solid mass. The mass keeps growing. It may stay in the kidney or move down the urinary tract and settle in the ureter.
If the stones are very small, they may pass out of your body in your urine without too much pain. But if they don’t pass, they cause urine to back up in the kidney, ureter, bladder or urethra. That’s when you get pain and other symptoms.
Who’s at risk of getting uric acid stones?
If you don’t drink enough water, you have a higher chance of developing uric acid stones and other kidney stones. Other risk factors include:
- Conditions such as obesity and Type 2 diabetes.
- Diet high in salt and sugar.
- Family history of kidney stones.
- Too much or too little exercise.
- Weight loss surgery.
- Taking certain medications, such as diuretics and immune suppressants.
How common are uric acid stones?
Researchers estimate that one in 10 people in the United States will have a kidney stone at some point in their lives. They’re more common in men than women. For men, the lifetime risk is about 19%. For women, it’s about 9%.
Most people don’t get kidney stones before age 30. But many cases can happen earlier in life, even among children.
Symptoms and Causes
What causes uric acid stones?
Uric acid stones form when:
- Levels of uric acid in the urine are too high.
- The urine is continually too acidic.
The main causes of high acidity in urine are:
- Problems processing uric acid or protein in your diet: These problems are often inherited, passed down from parents to children. When your body has trouble processing uric acid or protein, acid builds up in the urine. A related condition is gout, where people have high uric acid levels in the blood and painful crystal deposits in the joints.
- Foods high in purines: Animal proteins, such as beef, poultry, pork, eggs and fish contain high levels of purines. Organ meats, such as liver and kidneys, have the highest levels. If you eat a lot of animal proteins, uric acid may build up in your urine. It can settle and form a stone, either by itself or with calcium. Usually, diet alone won’t cause uric acid stones — they often occur in someone who has a high-purine diet and is prone to developing them.
Other causes of high levels of uric acid include:
- Carrying excess weight and having diabetes: These conditions can increase acidity levels in the urine.
- Certain medications and supplements: Taking diuretics (which help with water retention) or immune-suppressing medications can increase your uric acid level.
- Chemotherapy: People undergoing chemotherapy are prone to higher levels of uric acid.
What are the symptoms of uric acid stones?
Uric acid stones have similar symptoms to other types of kidney stones. The main symptom is pain, which results from irritation or blockages inside the kidneys or urinary tract. You may feel pain in your:
Other symptoms include:
What are the possible complications of uric acid stones?
Any type of kidney stone increases your risk of developing kidney disease. If you have a stone, you’re at higher risk of having another one in the next five to seven years.
Diagnosis and Tests
How are uric acid stones diagnosed?
Your healthcare provider will ask you about your medical history and do a physical exam. Then your provider will do other diagnostic procedures, including:
- Blood tests: A blood test can detect too much uric acid or calcium in your blood. These tests can also suggest or rule out other conditions that may be causing your symptoms.
- Urine test: Your provider may ask you to do a 24-hour urine test. You collect your urine over 24 hours so your provider can test it for calcium and uric acid.
- Imaging: You may need a CT scan or ultrasound to find uric acid stones in your urinary tract. These imaging scans can help find even small stones. Usually, providers don’t use abdominal X-rays because they may miss smaller stones.
- Stone analysis: You may need to urinate using a special strainer to catch any stones you pass. Your provider will send the stone to a laboratory for analysis to figure out what type of kidney stone it is. Analyzing the stone helps your provider determine the cause and how you can prevent it from happening again.
Management and Treatment
How are uric acid stones treated?
Small stones (less than 7 millimeters in diameter) may pass on their own. It can take up to three weeks to pass. Even if the stones pass on their own, it’s still important to talk to your provider so you can prevent stones from forming again.
The most important step in uric acid stone treatment is drinking plenty of water to:
- Reduce the concentration of minerals in urine. Fluids dissolve the minerals, allowing them to leave your body through urine.
- Encourage you to pee often, which flushes away materials that may form stones.
Providers recommend that you drink enough to produce about 2.5 liters of urine. To produce that much urine, you need to drink a little more than 2.5 liters of fluid. That’s because you lose fluid through sweating or exercise. Aim for drinking about 3 liters (or about 3.1 quarts) of fluids per day.
Although drinking any fluid counts, it’s best to drink water. Your provider may prescribe medications as well to make the urine less acidic.
Can medication treat uric acid stones?
Your provider may prescribe medications to:
- Reduce uric acid levels in your blood and urine.
- Keep your urine alkaline (the opposite of acidic).
- Dissolve the uric acid stones.
Alpha blockers are a type of medication that may help stones in the ureter pass faster. Your provider will talk to you about this option if it’s right for you.
Will I need surgery for uric acid stones?
You may need surgery if the stones:
- Are very large.
- Block the flow of urine.
- Cause infection.
- Do not pass after four to six weeks.
Treatment options include minimally invasive or noninvasive techniques:
- Shockwave lithotripsy: This noninvasive procedure uses high-energy sound waves to break up the stones. Shockwave lithotripsy does not use an incision and nothing enters your body.
- Ureteroscopy: During a ureteroscopy, your provider inserts an endoscope (a thin tube) through the ureter, the tube that leads from each kidney to the bladder. The provider removes the stone using a tiny basket. In some cases, the provider can break the stone into smaller pieces using a laser, and then remove the pieces.
- Percutaneous nephrolithotomy (PCNL): Providers use PCNL for larger stones. A surgeon makes a small incision in your back to access the kidney. They either remove the stone or break it up first and then remove it.
Your provider will send the stone or pieces of the stone to a lab for analysis.
How does drinking water help reduce the risk of uric acid stones?
Drinking a lot of water is one of the best things you can do to reduce the risk of uric acid stones and other kidney stones. Fluids help make your urine less concentrated with waste products. The water helps your body wash away chemicals, so stones don’t form.
You can check the color of your urine to see if you’re drinking enough. Dark-colored pee means you’re not drinking enough. Pee should be light yellow or clear.
What diet can help prevent uric acid stones?
Avoid or limit foods high in purines. Too much of this chemical causes your body to produce more uric acid. A high uric acid level leads to more acid in your urine, which results in uric acid stones forming.
To prevent uric acid stones, cut down on high-purine foods, including:
- Red meat.
- Organ meats.
- Beer and alcohol.
- Meat-based gravies.
- Sardines, anchovies and shellfish.
- Vegetables and fruits.
- Whole grains.
- Low-fat dairy products.
It also helps to limit sugary foods and drinks, especially those that have high-fructose corn syrup. And try to avoid crash diets, which can increase uric acid levels in your blood.
How else can I prevent uric acid stones?
You can take other steps to prevent uric acid stones:
- Drink at least 12 cups of fluids every day, preferably water.
- Maintain a healthy weight.
- Follow the Dietary Approaches to Stop Hypertension (DASH) diet, which can reduce both high blood pressure and the risk of kidney stones.
- Take any medications your provider prescribed to prevent uric acid stones from forming.
Outlook / Prognosis
What’s the outlook for people with uric acid stones?
The outlook for uric acid stones and other kidney stones is positive. Many times, stones pass on their own. You may not even need treatment. If you do need treatment, the treatment options are very successful. You’ll likely make a full recovery.
But there is a risk of the stones coming back. Talk to your provider about dietary changes and other steps you can take to prevent another stone.
When should I go to the ER for a uric acid stone?
Call your provider or go to the ER if you think you may have a kidney stone, and you have these symptoms:
- High fever (more than 101.5 F).
- Burning sensation or seeing blood when you pee.
- Intense pain.
- Nausea and vomiting that doesn’t go away.
- A medical condition that puts you at higher risk for kidney stone complications, such as diabetes, having only one kidney or any kidney problems.
How can I take care of myself?
If you’ve had a uric acid stone or you’re at high risk for one (or any kidney stone), take steps to stay healthy:
- Drink plenty of water.
- Follow a healthy diet.
- Take any medications or supplements your provider prescribed.
- Contact your provider if you have severe pain or other worrying symptoms.
What else should I ask my healthcare provider?
If you have a uric acid stone, ask your provider:
- What treatment will work best?
- Will I need surgery?
- How can I prevent a stone from forming again?
- What diet is right for me?
- Should I avoid any foods or beverages?
- Do I need to take any supplements?
A note from Cleveland Clinic
Uric acid stones are a type of kidney stone. When you have a high level of uric acid in your blood and urine, small stones can form. These stones can block the passage of urine out of your body, causing pain and other symptoms. Many uric acid stones pass on their own. Your provider may prescribe medication to help the stone pass. For larger stones, your provider may recommend noninvasive or minimally invasive procedures. These treatments include shockwave lithotripsy, ureteroscopy and PCNL. Treatments are successful, but uric acid stones may come back. Avoid or limit foods high in purines to reduce your risk. If you have pain in your side, burning when you pee or see blood in your urine, talk to your healthcare provider. The right diagnosis and treatment can help you feel your best.
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