What is a kidney stone?
A kidney stone is a hard, pebble-like deposit that forms in the kidney. It may be as small as a grain of sand or as large as a pearl. Some are as big as golf balls. A stone may be smooth, irregular in shape, or jagged. Most are yellow or brown in color. There are different types of kidney stones:
- Calcium stones. Calcium stones are the most common type of stones. Calcium is a normal part of a healthy diet and is used by bones and muscles. Calcium not used by the body goes to the kidneys where it is normally flushed out with the urine. In some people the calcium that stays behind bonds with other waste products to form a stone.
- Struvite stones. Struvite stones contain the mineral magnesium and the waste product ammonia. It may form after an infection in the urinary system.
- Uric acid stones. Uric acid stones may form when there is too much acid in the urine. This can be seen in people who have gout.
- Cystine stones. Cystine, one of the building blocks that make up muscles, nerves, and other parts of the body, can build up in the urine and form a stone. Cystine stones are rare. The form of the disease runs in families.
Kidney stones are one of the most painful disorders, and one of the most common problems of the urinary tract. These people are more likely to get them:
- Whites are more prone to kidney stones than African-Americans.
- Although stones occur more often in men, the number of women who get kidney stones has been growing.
- Kidney stones strike mostly people between age 20 and 40.
- Once a person develops more than one stone, he or she is more likely to get more stones.
What causes a kidney stone?A kidney stone develops from crystals that build up in the kidney. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. However, in some people, stones still form. Small crystals can travel through the urinary tract and pass out of the body in the urine without even being noticed. A larger stone can get stuck in a ureter, the bladder, or the urethra. This may block the flow of urine and cause great pain.
Who is at risk for kidney stones?
Risk factors that can be controlled:
- How much fluid you drink. If you don’t drink enough fluids and tend to be dehydrated, you are at a higher risk for kidney stones.
- Eating a diet that is high in protein, sodium, and dark green vegetables (oxalate-rich types of foods), can increase your risk for kidney stones.
- Being overweight increases insulin resistance in your body. Insulin resistance increases the amount of calcium filtered into the urine. In turn, this increases the risk of developing a kidney stone.
- Some medications can increase your risk of kidney stones. Common medications include diuretics and anti-viral medications.
Risk factors that cannot be controlled:
- Diseases that cause ongoing elevated levels of calcium in the blood. Increased calcium can cause dehydration from increased urine output. Remaining calcium deposits within the kidney solidify into a stone.
- Surgeries on the digestive tract including the intestines and gastric bypass can make you prone to chronic dehydration or diseases that cause chronic diarrhea and dehydration. These increase the risk for kidney stones because of the dehydrated state.
- Inherited factors or a family history of kidney stones can raise your risks.
- Personal history of recurrent urinary tract infections
- Women with low estrogen levels, either after menopause or removal of the ovaries, are at greater risk for kidney stone.
- Men between the ages of 30 and 50 are the most likely to get kidney stones.
- Diseases where uric acid levels increase (gout)
- Insulin resistance from diabetes can cause an increase the amount of calcium filtered into the urine which increases the risk of a kidney stone.
What are the symptoms of kidney stones?
The following are the most common symptoms of kidney stones:
- Extreme, sharp pain in the back or side that will not go away. Changing positions does not help. Pain can come and go.
- Blood in the urine (hematuria)
- Nausea and vomiting
- Cloudy or odorous urine
- Frequent urination
- A burning feeling when you urinate (dysuria)
- Fever and chills
Prompt medical attention for kidney stones is needed.
The symptoms of kidney stones may look like other conditions or medical problems. Always consult your health care provider for a diagnosis.
How are kidney stones diagnosed?
Your doctor will do a history and physical exam. You may have other tests including:
- Intravenous pyelogram (IVP). This is a series of X-rays of the kidney, ureters, and bladder with the injection of a contrast dye into the vein. It helps detect tumors, abnormalities, kidney stones, or any obstructions, and to check blood flow to the kidney.
- Computerized tomography (CT or CT scan). This imaging method uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body.
- Urinalysis. This is lab examination of urine for various cells and chemicals, such as red blood cells, white blood cells, infection, or excessive protein.
- Blood tests. This is lab examination of the blood to detect substances that might promote stone formation.
- Renal ultrasound. A noninvasive test in which a transducer is passed over the kidney producing sound waves that bounce off the kidney. It transmits a picture of the organ on a video screen. The test is used to determine the size and shape of the kidney, and to detect a mass, kidney stone, cyst, or other obstruction in the kidney.
What is the treatment for kidney stones?
Your health care provider will figure out the best treatment based on:
- How old you are
- Your overall health and medical history
- How sick you are
- How well you can handle specific medications, procedures, or therapies
- How long the condition is expected to last
- Your opinion or preference
Some kidney stones pass out of the body on their own without treatment. In cases that cause lasting symptoms or other complications, kidney stones may be treated with one of the following:
- Shock waves or extracorporeal shock wave lithotripsy (ESWL). This treatment uses a machine to send shock waves directly to the kidney stone. This breaks a large stone into smaller stones that will pass through the urinary system. There are two types of shock wave machines. In one, you sit in a tub of water. In the other, you lie on a table.
- Ureteroscope. A long wire with a camera attached to it is inserted into the urethra and passed up through the bladder to the ureter where the stone is located. A tiny cage is used to obtain the stone and remove it.
- Tunnel surgery (also called percutaneous nephrolithotomy). A small cut is made in your back and a narrow tunnel is made through the skin to the stone inside the kidney. The surgeon can remove the stone through this tunnel.
How can kidney stones be prevented?
The best ways to prevent kidney stones are:
- Drink more water. Up to 12 glasses of water a day can help to flush away the substances that form stones in the kidneys. Ginger ale, lemon-lime sodas, and fruit juices are also OK.
- Limit coffee, tea, and cola to 1 or 2 cups a day. The caffeine may cause a rapid loss of fluid.
- Consult your health care provider or a dietitian about any diet changes.
- Medications may be prescribed to prevent calcium and uric acid stones from forming.
When should I call my health care provider?If your symptoms get worse or you have new symptoms, let your health care provider know.
Key points about kidney stones
- A kidney stone is a piece of hard sediment that forms in the kidney. It develops when certain substances that are filtered in the urine crystalize and stick together in the kidney creating a stone.
- Most stones are made of calcium, although stones can be formed from other substances.
- Dehydration and certain medications also increase the risk for kidney stones.
- Kidney stones cause pain with urination as the stone passes through the urinary tract.
- Blood can also be seen in the urine.
- Some kidney stones can't be passed out of your body because they are too large and become stuck in the urinary tract. This causes great pain.
- Seek treatment right away for removal of kidney stones to prevent permanent damage to the kidneys or urinary tract.
- You may be able to prevent kidney stones by avoiding certain foods and drinking plenty of water.
- Once a person has a kidney stone, there is a strong likelihood another stone will develop.
Next stepsTips to help you get the most from a visit to your health care provider:
- Before your visit, write down questions you want answered.
- Bring someone with you to help you ask questions and remember what your provider tells you.
- At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
- If you have a follow-up appointment, write down the date, time, and purpose for that visit.
- Know how you can contact your provider if you have questions.