Kidney stones are hard deposits of minerals that form inside your kidneys. While many patients will describe kidney stones causing the worst pain of their life, many kidney stones can pass out of your body on their own. In some cases, surgery may need to be performed to remove kidney stones. As long as these stones pass or are treated, they usually do not cause any long-term damage.
What are kidney stones?
Kidney stones, also called nephrolithiasis, are solid pieces of material that develop when you have too much of a certain mineral in your urine. They usually result from a buildup of calcium. While their size and composition may vary, these stones usually come from the kidney and then can travel through the rest of your urinary tract.
Types of kidney stones
There are five main types, and each type of stone has a different cause.
- Calcium oxalate stones (the most common kind)
- Calcium phosphate stones
- Struvite stones (more common in women)
- Uric acid stones (more common in men)
- Cystine stones
What are the risk factors for kidney stones?
Certain conditions make it more likely that you might develop kidney stones. Some of them are controllable, and others are not:
- Low fluid intake. The most common cause of kidney stones is not drinking enough fluids.
- Diet. You are at higher risk if you eat a diet high in sodium and protein.
- Personal or family medical history of kidney stones. You’re more likely to develop kidney stones if you’ve had them before, or if a family member has had them.
- Obesity. People who are obese have higher rates of kidney stone formation.
- Medications. Taking medicines such as acetazolamide and indinavir can increase your risk.
- Medical problems. If you have diabetes, Crohn’s disease, hyperparathyroidism, gout, renal tubular acidosis or cystinuria, or you’ve had previous intestinal surgery like gastric bypass, you have a higher chance of developing kidney stones. Blockages in your urinary tract can also lead to kidney stones forming.
- Gender. While many used to believe kidney stones are more common in males, now they are thought to affect males and females relatively equally.
- Age. Kidney stones are more prevalent in people over age 30, but they are becoming more common in children.
Children are also at higher risk of kidney stones if they are immobile—for example, if they are in a cast after surgery. That’s because their bones may release extra calcium into the bloodstream.
What are the signs and symptoms of kidney stones?
When kidney stones pass through the urinary tract, they can cause a range of symptoms:
- Fluctuating, severe pain in the lower back that can radiate to the abdomen and groin
- Bloody urine
- Urine obstruction
- Frequent, sometimes difficult, flow of urine
- Nausea and vomiting
If you’re not sure what’s wrong and you’re concerned about your symptoms, contact your doctor. Your doctor can help determine if it’s kidney stones or another kidney problem causing your pain or discomfort.
Seek immediate medical care if you have excruciating pain (so severe you can’t get comfortable), or pain accompanied by any of the other symptoms listed above.
How can you avoid kidney stones?
You can reduce your chances of getting kidney stones by paying attention to your fluid intake and your diet:
- Drink two to three liters of water daily, or enough so that your urine is light yellow or clear. Adding lemon to your water may help, since the citric acid in lemon binds with calcium and can help prevent calcium stones from forming. Be sure to get plenty of fluids when the weather is warm—kidney stones are more common when the temperatures climb and people aren’t hydrating properly.
- Choose a diet low in sodium and animal protein.
- Reduce certain high oxalate containing foods. Additional testing is needed to confirm, but if you eat a very high amount of certain nuts and vegetables, these may increase your risk for developing kidney stones.
If you’ve had kidney stones in the past, these steps might help keep them from recurring:
- Your doctor may prescribe medication. There are different types of medications you can take, depending on what kind of mineral caused your kidney stones.
- If you take calcium supplements, talk to your doctor about discontinuing them, since they can increase your risk of kidney stones. But include plenty of high-calcium foods in your diet—the calcium you eat doesn’t increase your risk.
- Consult a dietitian about an eating plan that can reduce your odds of developing kidney stones.
How can you diagnose kidney stones?
If your symptoms indicate that you might have a kidney stone, your doctor may recommend different types of tests:
- Imaging tests such as a CT scan, X-ray or ultrasound can diagnose kidney stones.
- Blood tests, urinalysis or urine culture (urine testing) can check for signs of infection.
- Additional testing, such as a kidney function test or a biopsy, can help determine if something else might be causing your symptoms.
How can kidney stones be treated?
Most stones pass on their own when you urinate, especially if they are small. A 3 mm kidney stone has about an 80% chance of passing on its own. At about 5 mm, the odds are about 50%. If a kidney stone reaches 8 mm, the odds drop to 20%.
You’ll typically feel pain if the stone blocks the kidney and urine cannot drain. You’ll need treatment if there’s kidney swelling, which is called hydronephrosis.
If you have only one kidney, your doctor will want to treat any stones more aggressively, to reduce the risk of long-term damage and loss of kidney function.
For those stones that do not pass on their own, there are three main treatment options for kidney stone surgery:
- Extracorporeal shock wave lithotripsy. With this minimally invasive procedure, which can treat smaller kidney stones, your doctor uses X-rays to locate the stone. Once it’s located, sound waves from an ultrasound break the stone down into smaller pieces that you can pass in your urine. With this procedure, most people go home the same day.
- Ureteroscopy. This procedure involves inserting a small flexible scope into the urethra (the channel that allows urine to flow out of the body), through the bladder and into the ureter, which is the small tube that connects the kidney to the bladder. The surgeon can then use a laser to break the stone into smaller pieces or can remove the stones. There are no incisions, and this is typically a surgery where you can go home the same day.
- Percutaneous nephrolithotomy. Doctors usually use this procedure for larger kidney stones. The surgeon makes a small, 1 cm incision in your flank or lower back and creates a path into the kidney where a camera can see the stone. A special probe then breaks the stone into smaller pieces which can be removed through the small incision. You may stay in the hospital for one to two days after the procedure.
After a kidney stone passes or is removed, your doctor can analyze it to find out what type of kidney stone it is. (If you pass a stone at home, save it in a clean container.) This analysis can help determine what your risk factors are and if any medications can help prevent your kidney stones from recurring.