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This site is dedicated to helping its members stay current on the latest research and best practices in the field of urology.
The Kidney & Urology Foundation of America, Inc. is a national, not-for-profit organization dedicated to helping people avoid the debilitating effects of kidney and urologic diseases. The site includes a comprehensive library on urological disease and issues.
This government agency is part of the National Institutes of Health (NIH), an agency of the U.S. Department of Health and Human Services. Its mission is to conduct and support biomedical research and disseminate research findings to the public. The site includes a comprehensive section on kidney disease, including kidney stones.
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Nephrology Channel site is developed by, Inc. It features physician-developed information on a broad spectrum of urology-related topics.
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"I was on my way to work when it happened.  I managed to drive myself to the hospital, thinking I'd just turn myself in to die."  (Anonymous quote from a man after passing a kidney stone.) 

Pity the ancient Egyptians who must have gone through the same experience without the benefit of modern medicine.  Scientists have found evidence of kidney stones in a 7,000-year-old mummy and we can only imagine what it must have been like "BP" (before pain killers). 

What causes kidney stones?

Knowing the disorder has plagued mankind throughout the ages is small comfort for today's 5 percent of women and 10 percent of men with kidney stones.  The potential of passing a kidney stone is just one of those life experiences that strikes fear in the hearts of the bravest of us.  There is good news, though. Most people with kidney stones will have no symptoms, and unless stones are discovered by chance, they can live their lives in blissful ignorance. 
Kidney stones are one of the most common disorders of the urinary tract. Each year, they result in as many as 600,000 emergency room visits and over a million visits to primary care physicians.  And those numbers have been increasing over the past 20 years, particularly in women.

Here's what happens.  Urine contains substances known to both form stones and to prevent them.  Usually, these substances balance each other. When they don't, crystals can form and then bond together. As the surface area of a clump increases, even more minerals are attracted.  When enough crystals clump together, they form a stone.
Kidney stones can be as small as grains of sand or as large as golf balls and range in shape from smooth and round to jagged and spiked.  If a stone stays small enough, it can travel through the urinary tract and pass out of the body in the urine without being noticed.  A large stone that moves into the ureter can cause extreme pain, often described by sufferers as more painful than major surgery, broken bones or even childbirth.

The most common cause of kidney stones is inadequate fluid in the body (dehydration), resulting in concentrated urine.  Other factors that may increase risk include chronic urinary tract infections, some medications and certain genetic and metabolic diseases.


Quick Facts

  • Kidney stones are made of salts and minerals in the urine that stick together to form small "pebbles." They can be as small as grains of sand or as large as golf balls.  They range in shape from smooth and round to jagged and spiked.

  • There are different types of kidney stones. Most stones are a combination of calcium and oxalate.

  • Kidney stones are most prevalent in patients between the ages of 30 and 45, and the incidence declines after age 50.

  • 5% of all women have kidney stones, while 10% of all men are diagnosed with kidney stones. 

  • Men between the ages of 40 to 65 are three to four times more likely to develop kidney stones than women.

  • Caucasians are more prone to kidney stones than are African-Americans.

  • If one family member has a kidney stone, the risk of another family member developing a stone increases.

  • Once you have had kidney stones, you are likely to have more.  Without proper preventive treatment, recurrence rates are as high as 50 percent in the first five years and 80 percent in 10 years.

  • Fewer than half of people with incidental stones will go on to develop a painful kidney stone attack. 

  • About 90 percent of all stones that leave the kidney will pass through the ureter, without intervention, within three to six weeks. 

  • It is impossible to predict when a kidney stone attack will occur.

  • Eating citrus fruits and consuming lots of liquids-especially during the summer months-are the best approaches to avoiding kidney stones.

  • Call your doctor when you have:
    • Extreme pain in your back or side that will not go away
    • Blood in your urine (urine will appear pink)
    • Vomiting
    • Urine that smells bad or looks cloudy
    • A burning feeling when you urinate

These may be signs of a kidney stone that needs a doctor's care.

Ask Your Doctor

This list of questions is a good starting point for discussion with your doctor. However, it is not a comprehensive list.

  • Am I at risk for developing kidney stones?

  • What size are my kidney stones? 

  • How likely are they to pass without problem?

  • Do I need tests need to be done to determine their type or to precisely locate them?

  • What do you think is the cause of my kidney stones?

  • What type of treatment do you recommend?  Why?

  • If a procedure is recommended – why should I have this procedure? 
    • How effective is it?
    • What are the possible side effects?
    • How is it done?

  • Is there a special diet I should follow?

  • Have my kidney stones caused any damage to my kidneys?

  • Will I require further treatment after my kidney stone is eliminated?

Key Point 1

For most individuals, the acute onset of kidney stones occurs when the stone enters the ureter and causes severe pain.  Surprisingly, initial treatment can be simply water and and analgesics.

A kidney stone is defined as a hard, rock-like mass made of minerals in the kidney.  But, to those who have had the unfortunate experience of passing a large kidney stone, the definition is just one word:  agony.

Stones develop from chemicals filtered by the kidneys, such as calcium, uric acid and cystine. When other chemicals, such as citrate and magnesium, don't provide sufficient balance, crystals are formed and then clump together on the inner surfaces of the kidney.

It's not unusual to be symptom free but still have kidney stones.  It's only when a stone of significant size breaks loose and begins to work its way down the ureter that you experience pain.   The onset of pain is usually sudden and dramatic, typically in the area of the kidney or in the lower abdomen. It may radiate to the groin.  The severity of pain depends on the size of stone and how much of a blockage it creates.  Other symptoms may accompany the pain such as:

  • Nausea and vomiting
  • Blood in the urine
  • Frequent urge to urinate
  • Burning sensation during urination
  • Fever (when infection is present)

Since most kidney stones will pass without intervention, treatment is usually ‘‘wait and watch'' while the patient takes pain medications and aggressively hydrates, drinking at least 2 to 3 quarts of liquid per day.  In some cases, a doctor may prescribe antibiotics to fight infection, an antispasmodic to relax the ureter or diuretics to prevent urine from staying in the kidney. 

While small stones can pass through the body within hours or a few days, larger stones can take several weeks.  During that time, the patient is usually asked to strain their urine to catch the stone.  Its chemical make-up can be analyzed to provide clues on how to prevent recurrence.  If a stone doesn't pass in a reasonable time, patients are usually referred to a urologist.   When a patient repeatedly suffers from kidney stones they may be referred to a nephrologist.


Key Point 2

If a kidney stone does not pass on its own, it must be removed mechanically to avoid kidney damage. 

A kidney stone may need to be removed if it:

  • Doesn't pass after a reasonable period of time
  • Is too large to pass on its own
  • Blocks the flow of urine
  • Causes ongoing urinary tract infection or bleeding
  • Is damaging the kidney or ureter

Kidney stones are usually not life-threatening, but they do increase the chance of urinary and kidney infection.   In rare cases a urinary infection can lead to septicaemia (when germs spread into the bloodstream).  Stones that block urine flow can reduce kidney function and even cause permanent kidney damage.

If a stone needs to be removed, the urologist has several choices depending on circumstances. 

If the stone...The urologist will most likely:
Is near the bladderInsert a scope into the bladder and through the ureter to retrieve it (called Ureteroscopy)
Is near the kidneyUse shock waves to break the stones into smaller fragments that can then be passed (called Extracorporeal Shockwave Lithotripsy)
Can't be removed with either of the two methods aboveMake a small incision in the back to insert a scope into the kidney (called Percutaneous Nephrolithotomy)

The surgeon inserts a small, flexible, telescope-like instrument into the urethra, through the bladder and into the ureter to remove the stone. An advanced form of ureteroscopy uses a laser to vaporize the stone.

Extracorporeal Shockwave Lithotripsy
This is the most frequently used procedure for the treatment of kidney stones. A machine called a lithotripter creates sonic shock waves that travel through the body until they hit the stones and break them into small particles so they can be easily passed.  Sometimes a stent (a small tube) is inserted through the bladder into the ureter to help the fragments pass.
Percutaneous Nephrolithotomy
This technique can be used if the stone is too large or located in an area not suitable for lithotripsy. It involves making a tiny cut in the back, then using a nephroscope (a small instrument used in minimally invasive surgery) to locate and remove the stone


Key Point 3

Long-term prevention of kidney stones is possible for most patients.  For starters, patients must drink a lot of water and follow low sodium, normal calcium diets.  

People who have had more than one kidney stone are likely to form another. Without proper treatment to prevent recurrence, the rate is as high as 50% in the first five years and 80% in ten years.  Fortunately, there are things that can be done to dramatically improve the odds.

The first step is to identify the stone.  The four types are:


Calcium75 to 80% of casesCalcium and/or oxalate or phosphate
Struvite10 to 15% of casesInfection in the urinary tract
Uric acid5 to 10% of casesUric acid (a by-product of protein metabolism)
Cystine1% of casesCystinuria (a hereditary condition)

A doctor will do in-depth family and medical histories, a physical exam, common urine and blood tests and a 24-hour urine collection test to measure urine volume and levels of acidity, calcium, sodium, uric acid, oxalate, citrate and creatinine.  If the patient was able to catch a stone when it passed, it can be analyzed. 

The most important step to prevent kidney stones of any type is to drink enough liquid throughout the day to produce at least 2 quarts of urine in every 24-hour period. Water is best. Soft drinks may acidify the urine and contribute to stone formation.  More fluid is needed after exertion, during warm weather and during times of stress. 

In addition, once the cause of the stone is found, medications or changes in diet may be used to help prevent new stones.

In general, scientists don't think that eating any specific foods causes stones to form in people who are not already susceptible. In susceptible people, however, diet changes appear to help.  Depending on the type of stone, recommended changes might include:

  • Limiting meat protein to eight ounces a day
  • Reducing foods high in oxalate, such as spinach, okra, beets and rhubarb
  • Increasing fiber-rich foods
  • Restricting salt intake to less than 2,000 mg per day

Restricting calcium intake is NOT recommended.  In fact, doing so might actually increase the risk of forming kidney stones since dietary calcium helps to bind up oxalate in the colon.  Doctors generally recommend a diet with normal amounts of calcium.

Some people will need medication to prevent stones from forming.  The choice of medicine depends on the type of kidney stone.

  • Thiazides reduce the amount of calcium in the urine, which may prevent calcium kidney stones.
  • Calcium carbonate and calcium citrate may be used to prevent kidney stones in people with high levels of oxalate.
  • Orthophosphate helps prevent calcium stones that do not contain a lot of oxalate.
  • Medications that prevent the urine from becoming too acidic help prevent uric acid stones.

The good new is that doctors have achieved very high success rates at preventing kidney stones with patients who are compliant (they faithfully follow fluid intake, diet and medication regimens).

Medline Plus

Medline Description: 

Conduct an off-site search for Kidney Stones information from MedlinePlus.  These up-to-date search results are based on search terms specific to Second Opinion Key Points.

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