Preventing kidney stones

If you've had a kidney stone, there's a 50% chance you'll develop another one within 7 to 10 years. Luckily, there are steps you can take to reduce your chances of future stones.

How did I get this stone?
The simplest way to describe this complex process is that stones occur when the urine is too concentrated in natural substances that can clump together and grow into stones.

Kidney stones (calculi) are made of substances normally found in the urine. Stones begin as small crystals in the kidney. They form when the urine is too concentrated in calcium or other chemicals that can group together. Over time, tiny crystals may grow into stones that are large enough to cause symptoms such as pain or bleeding. Stones grow in an unpredictable fashion. They can grow in quick spurts or extremely slowly, depending on conditions in the urine.

About 90% of kidney stones contain calcium. Most commonly, the crystals are made of calcium oxalate and occasionally they are made of calcium phosphate. Less common stone types are uric acid, cystine and struvite.

Can I avoid future stones?
At the HealthEast Kidney Stone Institute, we pay careful attention to emerging research and attempt to make our own contributions to this general body of knowledge.

To date, no program has been demonstrated to be 100% effective for all people. A reasonable expectation is to extend the interval between stones and in some cases avoid recurrence entirely. It is important to think of recurrent stones like any other disease such as high blood pressure or high cholesterol. For patients with severe stone disease, lifelong treatment is necessary to avoid recurrence.

We examine urine and blood samples
We test the urine and blood and attempt to make adjustments through behavioral, dietary or medication recommendations. We then perform follow-up studies to confirm that we have had the desired effect and make further recommendations to give you the best chances of preventing future stones.

We incorporate results of population studies into our practice
We attempt to be as specific as possible in our interventions and advice. We do not ask patients to do anything unless there is good evidence to believe that it will be effective for their particular age, sex, diet, habits or urine and blood chemistry.

Decreasing your chances for recurrence
If you're experiencing kidney stones for the first time (and have stones made of calcium oxalate), small changes in diet and habits are often the best way to keep stones from recurring.

Risk evaluation tests
A comprehensive risk evaluation may be recommended if you have atypical stones, multiple stones, frequent recurrences or are highly motivated to avoid future stones.

The following tests are generally included:

Analysis of the stone(s)
A simple blood test
24 hour urine collection on two occasions
A dietary diary around the time of urine collection

From these three tests, your doctor may detect disorders and can discuss specific prevention strategies with you.

Tips for all stone types

Drink more fluids - This is the best thing you can do to help
prevent stones!
Maintain a normal calcium diet
Avoid excess salt
Lose weight if you are obese

Why is fluid so important?
Drinking more liquids is the best way you can help prevent future stones. Stones begin to form when substances in the urine are too concentrated. The more you drink, the more urine you will make. This means all substances in the urine will be less concentrated.

How much urine should I be producing?
The usual recommended daily urine production is about 2 to 3 quarts (2000-3000 ml). If you are producing more than 3 quarts of urine on a regular basis, it is possible to deplete important minerals stored in the body.

Measure the amount you produce in a day

Collect all urine in a jug and measure at the end of the day
Use a measuring cup with each void and add up the numbers at the end of the day

Observe

Color - Dark amber urine is concentrated. Light straw color or lighter is dilute and desirable
Odor - Concentrated urine tends to smell stronger. Dilute urine is nearly odorless
Specific gravity - can be measured with urine dipsticks in your doctors office

Tips for increasing your fluid intake
Increasing the amount of fluid you drink is effective for all types of kidney stones. While water is commonly recommended, all fluids are effective for increasing the amount of urine your body produces.

Focus on starting a lifelong habit, rather than a short-term solution.
Keep liquids on hand that you like.
Drink out of larger glasses. You'll tend to drink more with each serving.
Have an additional glass of fluid with each meal.
Keep a water or drink bottle at work and fill it regularly.
Drink from water fountains when you see them.

*If you are prone to fluid retention, consult your doctor before making changes to your fluid habits.

Normal calcium diet
When it comes to kidney stones, many doctors recommend maintaining a normal calcium intake. Researchers have found that people with higher calcium intakes tend to have fewer stones. Foods with high calcium content include:

Dairy products (including milk, cheese and yogurt)
Meat and fish
Enriched cereals

What about calcium supplements?
Many people take calcium supplements, either on their own or as prescribed by a doctor. Research has indicated that calcium supplements do not usually pose a risk for stone formation. Click here to learn more.

Low salt diet
Salt (sodium chloride) is found in abundance in many foods. High sodium levels in the urine can interfere with the kidney's handling of calcium. High urine sodium levels can make it easier for uric acid crystals to form. They can grow into stones or act as seeds for calcium stones.

Tips for reducing the salt in your diet:

Don't use salt at the table
Reduce the salt used in food preparation. Try 1/2 teaspoon when recipes call for 1 teaspoon.
Use herbs and spices for flavoring instead of salt.
Avoid salty foods
Check the label before you buy or use a product. Note sodium and portion size information

Examples of foods with high sodium content

Processed meat (including luncheon meats, sausage)
Crackers
Instant cereal
Processed cheese
Canned soups
Chips and snack foods
Soy sauce

Examples of foods with low sodium content

Fresh meat
Unsalted crackers
Rice
Fruits and vegetables - fresh or frozen
Milk
Hard candy
Sugar
Salt substitutes

Tips for preventing specific stone types

About 90% of kidney stones contain calcium. Most commonly, the crystals are made of calcium oxalate and occasionally they are made of calcium phosphate. Less commonly, stones are made of uric acid, cystine or struvite.

Calcium oxalate stones
For those with calcium oxalate stones, it may help to avoid foods that are high in oxalate. Oxalate is a natural chemical found in many foods. Of the oxalate found in urine, about two-thirds is produced by the body's metabolism and one-third comes from dietary sources.

Unfortunately, researchers are not sure how much oxalate found in a particular food gets absorbed by the body. Therefore, the oxalate content of a food may be misleading. Some foods that are particularly rich in oxalate include:

Spinach
Chocolate
Nuts

A comprehensive list can be found at Litholink.com

Uric acid stones
For those with uric acid stones, it may help to avoid foods that are high in purine content. Metabolism breaks purines down to uric acid (a waste product). If uric acid builds up in the body or the urine, it can lead to gout or kidney stones made of uric acid. For people with a history of gout or uric acid stones, most doctors recommend reducing the amount of purine in the diet.

High purine foods

Liver and other organ meats
Anchovies, sardines, herring
Scallops, mussels
Meat extracts

Moderately high purine foods

Asparagus, cauliflower, spinach, mushrooms, green peas
Meat, poultry
Fish, shellfish
Dried peas,
Beans/lentils

Struvite stones
Treat urinary tract infections aggressively.

No matter what kind of stone you have, your doctor can give you specific advice.

For mor tips
Click here for tips that apply to all stone types.

Stone Prevention Evaluation

At the Healtheast Kidney Stone Institute, we offer stone prevention services to all patients. The type of evaluation is determined by your needs.

Basic evaluation

Blood test to help determine your stone risk
Stone analysis (if stones are available)
Discussion with your doctor on preventing future stones.
Advice may include:
- Increasing fluid intake
- Maintaining a normal intake of calcium
- Eating a low sodium diet
- Losing weight (if overweight)

Comprehensive evaluation

Blood test to help determine your stone risk and parathyroid hormone
Two 24 hour urine collections
Stone analysis (if stones are available)
Diet survey
Discussion of individual stone risks and creation of a stone prevention strategy

Follow-up studies and intervention

After an evaluation, your doctor may suggest follow-up studies or prevention strategies, including:

Specific dietary changes
Medication
Repeat blood and urine tests in one month
Further intervention until stone risk factors normalized

Stones and diet - common myths

Myth: Dietary calcium causes stones
It would seem to makes sense that if you develop kidney stones made of calcium, you should stay away from calcium in food. This turns out to be incorrect. Studies have found that the more people avoid calcium, the more likely they are to develop stones.

Calcium and oxalate bind together in the body like magnets to form stone crystals. If calcium and oxalate meet in the urine, they can form a stone. However, if calcium and oxalate meet in the stomach, they still stick to each other but will not be absorbed into the body. This is why we treat some people with high oxalate levels in the urine with calcium supplements.

Myth: Water is the only liquid that helps prevent stones
Many people believe that only water is effective for preventing stones. This belief can be frustrating for those who don't like to drink water or have water that tastes "bad." Studies have clearly shown that drinking more of anything can reduce the occurrence of stones. This makes sense because the basis of almost anything you drink is water with additives for color and taste.

Myth: Coffee, tea and carbonated drinks cause stones
While many people believe that these drinks cause stones, studies clearly show that they do not increase the risk of stones.

Whatever potential risks may be associated with caffeine, oxalate (in some teas) or phosphoric acid (in carbonated beverages) appears to be overwhelmed by the preventative effects of the water that makes up the majority of the drink. The only drink that has been shown to increase risk of stones is grapefruit juice, although the reason is not well understood.

Myth: Alcohol causes stones
There is concern that the diuretic effect of alcohol may dehydrate people and be a risk for stone formation. Interestingly, in studies, beer and wine were found to significantly decrease the risk of stone formation. While it is not recommended to overindulge, moderate alcohol use will not increase the risk for stones.

Myth: Vitamin C is bad
While the body may break Vitamin C down into to oxalate, normal amounts of the vitamin do not appear to impact the risk of developing kidney stones.

References

1: Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol. 2004 Dec;15(12):3225-32.

2: Curhan GC, Willett WC, Knight EL, Stampfer MJ. Dietary factors and the risk of incident kidney stones in younger women: Nurses' Health Study II. Arch Intern Med. 2004 Apr 26;164(8):885-91.

3: Taylor EN, Curhan GC. Role of nutrition in the formation of calcium-containing kidney stones. Nephron Physiol. 2004;98(2):p55-63.

4: Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Twenty-four-hour urine chemistries and the risk of kidney stones among women and men. Kidney Int. 2001 Jun;59(6):2290-8.

5: Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Intake of vitamins B6 and C and the risk of kidney stones in women. J Am Soc Nephrol. 1999 Apr;10(4):840-5.

6: Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Beverage use and risk for kidney stones in women. Ann Intern Med. 1998 Apr 1;128(7):534-40.

7: Curhan GC, Willett WC, Speizer FE, Spiegelman D, Stampfer MJ. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med. 1997 Apr 1;126(7):497-504.

8: Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men. J Urol. 1996 Jun;155(6):1847-51.

9: Curhan GC, Willett WC, Rimm EB, Spiegelman D, Stampfer MJ. Prospective study of beverage use and the risk of kidney stones. Am J Epidemiol. 1996 Feb 1;143(3):240-7.