The James Buchanan Brady Urological Institute
 
 
 
   KIDNEY STONES            Print this page

  HOW CAN KIDNEY STONES BE PREVENTED?

If you have had one kidney stone, you are likely to form another. To reduce your chances of forming another stone, the first step is to determine why your original stone formed in the first place. At the Brady Urological Institute at Johns Hopkins, we believe in the adage, “An ounce of prevention is worth a pound of cure,” so we place great emphasis on a thorough metabolic evaluation, so that therapies can be appropriately directed towards reducing the risk of recurrent stone disease.

If you passed your stone on your own, and still have it, your doctor will send it to a laboratory to be analyzed to see what it is made of. Usually, if your stone is removed by ureteroscopy or PERC, your doctor will send a piece of the stone for analysis, too. The composition of a stone is an important piece of information to know, as treatment is specific to the type of stone.

Because we know that kidney stones form when the urine has too high a concentration of crystals and/or not enough substances that protect against the crystals, a detailed analysis of the metabolism of a stone former is important. Typically, the metabolic evaluation of a stone former consists of a simple blood test and two 24 hour urine collections.

The results of these metabolic studies will provide an assessment of the risk of future stone formation. One or more of the following diagnoses and treatments may be made based on these metabolic data.

Diagnosis: Low urine volume.
Treatment: Increase fluid intake

The most basic thing you can do to prevent stone formation is to drink more fluids, thereby diluting your urine. Your goal should be to urinate more than two liters per day. All fluids count towards this goal, but water is, of course, the best.

Diagnosis: Too much calcium in the urine (hypercalciuria)
Possible Treatments:

Thiazide diuretics
These drugs help to decrease urine calcium excretion. They also help to keep calcium in the bones, reducing the risk for osteoporosis. The most common side-effect of thiazide diuretics is potassium loss, so in many cases your doctor will prescribe a potassium supplement to go along with the thiazide diuretic.

Low sodium intake
The human body carefully regulates its sodium levels. When excess sodium is excreted in the urine, calcium is also excreted proportionally. In other words, the more sodium you consume, the more calcium that will be in your urine. Your goal should be to reduce your sodium intake so that you consume less than 2 grams of sodium per day. Watch out for “silent sources” of salt, such as fast foods, packaged or canned foods, softened water, and sports drinks.

Normal calcium diet
Stone formers sometimes think that because there is too much calcium in their urine, they should restrict their calcium intake. There is no research that supports this practice. Your body needs dietary calcium to support the skeleton. You should be encouraged to consume two servings of dairy (between 800 and 1,200 mg per day) or other calcium-rich foods to maintain bone stores of calcium. For patients who form calcium oxalate stones, it is doubly important to consume adequate dietary calcium, because under normal circumstances calcium and oxalate bind together in the intestine and are eliminated from the body. If there is no calcium to join with oxalate, the oxalate will be reabsorbed by your body and passed into the urine where it may increase the risk of calcium oxalate stones.

Increase fluid intake
No matter what your diagnosis, you should drink enough water to produce at least 2 liters of urine per day.

Diagnosis: Hypocitraturia (too little citrate in the urine)
Possible Treatments:
Citrate supplementation
Citrate is a molecule that binds to calcium in the urine, preventing calcium from binding to oxalate or phosphate and forming a stone. If your potassium level is low or normal, your doctor may prescribe potassium citrate supplement. If you have high blood potassium levels, your doctor may prescribe a sodium citrate supplement, such as Bicitra or sodium bicarbonate.
There is some evidence that citrus juices, such as orange juice or lemonade may increase urinary citrate levels, so these fluids would be particularly good for patients with hypocitraturia.

Diagnosis: Hyperoxaluria (too much oxalate in the urine)
Possible Treatments:
Low Oxalate Diet
If you form calcium oxalate stones, it is important that you limit your intake of dietary oxalates. Many healthy foods contain oxalate, so rather than exclude these foods entirely, we just ask that you limit those foods that are particularly high in oxalate. If you do consume foods high in oxalate, be sure to flush out the extra load of oxalate with an added glass or two of water.

Normal Calcium Diet
Oxalate and calcium bind together in the intestine and leave the body together in the stool. If there is not enough calcium, then the extra oxalate will have nothing in the intestine to bind to, so it will be absorbed into the bloodstream and end up in the urine, where it will form a calcium oxalate stone.

Increase Fluid Intake
No matter what your diagnosis, you should drink enough water to produce at least 2 liters of urine per day.

Hyperuricosuria (too much uric acid in the urine)
Possible Treatments
Low protein diet

Most Americans far exceed the necessary protein intake, which can lead to too much uric acid in the urine. As a general recommendation, limit your daily protein intake to 12 ounces per day of beef, poultry, fish, and pork. Twelve ounces is equivalent in size to about three decks of cards. This will be plenty of protein to meet your body’s needs.

Allopurinol
If you have tried a low protein diet and you still have too much uric acid in your urine, your doctor may prescribe the drug Allopurinol. This drug acts to reduce the uric acid levels in the urine, by blocking the conversion of purines to uric acid.

Increase Fluid Intake
No matter what your diagnosis, you should drink enough water to produce at least 2 liters of urine per day.

Diagnosis: Low Urine pH (too much acid in the urine)
Possible Treatments:
Citrate Supplementation

Citrate supplements, such as potassium citrate, will raise the pH of your urine, making stones, such as those composed of uric acid, less likely to form. If your blood potassium level is high, your doctor may prescribe sodium bicarbonate or Bicitra.

Lower Protein Intake
A diet high in protein will reduce urinary pH. As a general recommendation, limit your daily protein intake to 12 ounces per day of beef, poultry, fish, and pork. Twelve ounces is equivalent in size to about three decks of cards. This will be plenty of protein to meet your body’s needs.

Increase Fluid Intake
No matter what your diagnosis, you should drink enough water to produce at least 2 liters of urine per day.





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