There are several types of kidney stones. All of them can be painful. But how you treat them and prevent new ones from forming depends on the type of stone you have, according to Timothy D. Averch, M.D., Professor and Vice Chair for Quality of Urology in the Department of Urology at the University of Pittsburgh Medical Center and Director of the UPMC Kidney Stone Center.
What are Kidney Stones?
Normally, urine contains many dissolved substances. At times, some materials in the urine may become concentrated and form solid crystals. When materials continue to build up around the crystals, they can lead to the development of stones. Stones formed in the kidney are called kidney stones. Sometimes, the kidney stone can travel down the ureter, the tube between the kidney and the bladder. If the stone reaches the bladder, it can be passed out of the body through urine. If the stone becomes lodged in the ureter, it blocks the urine flow from that kidney and causes pain.
The majority of stones contain calcium. Most calcium stones are made of a material called calcium oxalate. Others are made of calcium phosphate. Some people have too much calcium in their urine, raising their risk of calcium stones. Even with normal amounts of calcium in the urine, calcium stones may form for other reasons. "A common misconception is that drinking too much milk causes calcium stones," Dr. Averch said. "That's almost never the case."
There are several types of non-calcium stones. These are:
- Uric acid stones. Uric acid is a waste product that comes from chemical changes in the body. Uric acid crystals do not dissolve well in acidic urine and instead will form a uric acid stone.
- Struvite/infection stones. These stones are related to chronic urinary tract infections.
- Cystine stones. Cystinuria (too much cystine in the urine) is a rare, inherited metabolic disorder. It is when the kidneys do not reabsorb cystine from the urine. When high amounts of cystine are in the urine, it causes stones to form.
Kidney stones often have no definitive, single cause. If you have kidney stones, your doctor will evaluate your blood and urine to figure out contributing factors that may be increasing your risk of stones.
Kidney Stone Symptoms
Some kidney stones are "silent," meaning they cause no symptoms. Often, a person knows they have stones when they have sudden pain while the stone is passing.
Common symptoms of kidney stones are:
- A sharp, cramping pain in the back and side, often moving to the lower abdomen or groin. The pain often starts suddenly and comes in waves. It can come and go as the body tries to get rid of the stone.
- A feeling of an intense need to urinate.
- Urinating more often or a burning feeling during urination.
- Urine that is dark or red due to blood. Sometimes urine has only small amounts of red blood cells that can't be seen with the naked eye.
- Nausea and vomiting.
- Pain at the tip of the penis.
Treatment of kidney stones depends on where the stone is, how big it is and what symptoms it is causing, Dr. Averch said. "If it's a small stone, we typically give it time to see if it passes naturally without any intervention," he said. "But if the symptoms are significant, the stone is affecting kidney function or there are signs of infection, then treatment may be needed quickly."
There are three treatment options:
- Shock wave lithotripsy, used to treat stones in the kidney and ureter. Shock waves are focused on the stone using X-rays or ultrasound to pinpoint the stone. Repeated firing of shock waves on the stone usually causes it to break into small pieces. These smaller pieces of stones pass out in the urine over a few weeks.
- Ureteroscopy, used to treat stones in the kidney and ureter. The procedure involves passing a very small telescope, called an ureteroscope, into the bladder, up the ureter and into the kidney. Once the stone is located, it is broken up using laser energy and then removed with a basket-like device.
- Percutaneous nephrolithotomy is used to treat large stones in the kidney. The procedure involves making an incision in the back or side, to allow a rigid instrument called a nephroscope to be passed into the hollow center part of the kidney where the stone is located. An instrument passed through the nephroscope breaks up the stone and suctions out the pieces.
Preventing Future Stones
Once your doctor finds out why you are forming stones, he or she will give you tips on how to prevent them. "There are general rules about what food and drink to avoid in order to reduce your risk of kidney stones," Dr. Averch said. "However, there are a multitude of factors that can contribute, and everyone's specific risk factors are a little different. For some people that may be salt, while for others it could be animal proteins or oxalates (a naturally occurring compound in foods like spinach and nuts). That's why it's important for your doctor to determine your individual risk factors."
A major risk factor for kidney stones is constant low urine volume. People who have a history of kidney stones should drink plenty of water-enough to produce two liters (half a gallon) of urine a day, Dr. Averch said. "We tell our patients to measure how much urine they are producing-there's no other way to be sure," he noted. For many people, that translates to drinking at least 3 liters of liquid each day. This equals about 3 quarts (about ten 10-ounce glasses). Use a household measuring cup to measure how much liquid you drink for a day or two.
Depending on the type of kidney stone, your doctor may prescribe medications to help prevent stone formation.
"Kidney stones should be treated like other chronic diseases," Dr. Averch said. "That means if you have a history of kidney stones, you shouldn't just think about them when they occur. If you have diabetes, you don't just treat it when you have a blood sugar spike-you treat it all the time. If you have asthma, you don't just pay attention to it when you have an asthma attack. Likewise, if you have a history of kidney stones, you should be working with your doctor to make whatever changes are needed to prevent them in the future."
Learn more in our Kidney Stones Urologic Conditions Article.