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 cars. 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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