Your kidneys remove waste and fluid from your blood to make urine. Sometimes, when you have too much of certain wastes and not enough fluid in your blood, these wastes can build up and stick together in your kidneys. These clumps of waste are called kidney stones.
Kidney stones have many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together.
Passing kidney stones can be quite painful, but the stones usually cause no permanent damage if they’re recognized in a timely fashion. Depending on your situation, you may need nothing more than to take pain medication and drink lots of water to pass a kidney stone. In other instances — for example, if stones become lodged in the urinary tract, are associated with a urinary infection or cause complications — surgery may be needed.
Not all kidney stones are made up of the same crystals. The different types of kidney stones include:
1. Calcium: Calcium stones are the most common. They’re often made of calcium oxalate (though they can consist of calcium phosphate or maleate). Eating fewer oxalate-rich foods can reduce your risk of developing this type of stone. High-oxalate foods include:
However, even though some kidney stones are made of calcium, getting enough calcium in your diet can prevent stones from forming.
2. Uric acid: This type of kidney stone is more common in men than in women. They can occur in people with gout or those going through chemotherapy.
This type of stone develops when urine is too acidic. A diet rich in purines can increase urine’s acidic level. Purine is a colorless substance in animal proteins, such as fish, shellfish, and meats.
3. Struvite: This type of stone is found mostly in women with urinary tract infections (UTIs). These stones can be large and cause urinary obstruction. They result from a kidney infection. Treating an underlying infection can prevent the development of struvite stones.
4. Cystine: Cystine stones are rare. They occur in both men and women who have the genetic disorder cystinuria. With this type of stone, cystine — an acid that occurs naturally in the body — leaks from the kidneys into the urine.
A kidney stone may not cause symptoms until it moves around within your kidney or passes into your ureter — the tube connecting the kidney and bladder. At that point, you may experience these signs and symptoms:
Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves through your urinary tract.
Make an appointment with your doctor if you have any signs and symptoms that worry you.
Seek immediate medical attention if you experience:
Anyone can get a kidney stone, but some people are more likely than others to have them. Men get kidney stones more often than women do. Kidney stones are also more common in non-Hispanic white people than in people of other ethnicities. You may also be more likely to have kidney stones if:
If your doctor suspects you have a kidney stone, you may have diagnostic tests and procedures, such as:
Treatment for kidney stones varies, depending on the type of stone and the cause.
Most small kidney stones won’t require invasive treatment. You may be able to pass a small stone by:
Kidney stones that can’t be treated with conservative measures — either because they’re too large to pass on their own or because they cause bleeding, kidney damage or ongoing urinary tract infections — may require more-extensive treatment. Procedures may include:
Prevention of kidney stones may include a combination of lifestyle changes and medications.
You may reduce your risk of kidney stones if you:
Ask your doctor for a referral to a dietitian who can help you develop an eating plan that reduces your risk of kidney stones.
Medications can control the number of minerals and salts in your urine and may be helpful in people who form certain kinds of stones. The type of medication your doctor prescribes will depend on the kind of kidney stones you have. Here are some examples: