Kidney Stones Prevention
This is probably the most important factor
in kidney stone management Once kidney stones have been treated and obstruction
relieved, patients need to undergo a metabolic workup which
should include stone analysis, drawing of blood to complete
a serum stone profile, and collection of a 24 hour urine
specimen. By performing these three laboratory tests, your
urologist may be able to suggest fluid and dietary changes
or medication to help prevent further stone formation.
The blood test should check serum calcium,
uric acid, phosphate, potassium, chloride, bicarbonate,
albumin, and creatinine. If the serum calcium level is elevated,
further blood should be drawn to check for PTH, parathyroid
hormone level, as elevated blood calcium may indicate hyperparathyroidism.
The 24 hour urine should check for total volume, calcium,
oxalate, uric acid, citrate, magnesium, phosphate, sodium,
and pH.
General Considerations
Stone formers are advised to drink enough fluids to put
out at least 2 quarts of urine per day. This urine flow
washes crystals from the system before they begin adhering
to make a stone. Fluids high in citrate are emphasized as
the citrate acts as an inhibitor to stone formation. Lemonade
made with frozen concentrate, real lemon juice or real lemons
is one of the fluids recommended for its citrate content.
Diets low in protein help to prevent stone
formation, so patients are advised to cut back on meat,
fish, and chicken. Stone formers are not good candidates
for high protein, high fat, low carbohydrate diets.
Diets low in sodium are effective in reducing
stone formation by decreasing the excretion of calcium.
The role of calcium restriction is controversial.
It is helpful in certain stone formers to reduce calcium
intake, but for the most part, patients are instructed
to eat a normal calcium diet without supplements. Often
the calcium binds with oxalate and is excreted, thereby
lowering the chance of stone disease.
Also stone formers should avoid stone provoking
drugs such as certain diuretics, calcitrol, or probenicid.
Specific Therapy
Calcium Stones
Patients diagnosed with absorptive hypercalciuria type I
are treated with thiazide diuretics to decrease urinary
calcium excretion. These diuretics such as Chlorthalidone
or hydrochlorothiazide sometimes deplete body potassium
so often potassium citrate is added to replace potassium
and for the inhibitory effect of citrate on stone formation.
Urocit K tablets, Polycitra-K crystals or syrup are used.
Patients with absorptive hypercalciuria
type II may respond to dietary calcium restriction and
sodium restrictions, but may also need a thiazide diuretic
and potassium citrate.
Absorptive hypercalciuria type III is treated
with Orthophosphate, Neutra-Phos-K.
Renal leak hypercalciuria is treated with
thiazide diuretics and potassium citrate supplementation.
Patients with hyperuricosuria may develop
calcium stones. The calcium layers out on a uric acid crystal.
Diet change is extremely important in these patients. Meat,
fish, chicken are restricted due to breakdown products that
produce uric acid crystals. K Citrate will also alkylinize
the urine to keep urine pH between 6.5-7.5 so uric acid
crystals remain in solution and are excreted. Sometimes
Allopurinol is recommended when serum uric acid level is
significantly elevated or urinary uric acid is significantly
elevated.
Hypocitrauria leads to stone formation and
is corrected with potassium citrate supplementation.
Hyperoxaluria is found in bowel disorders
such as inflammatory bowel disease, after certain gastric
bypass procedures. Lowering dietary fat and oxalate along
with calcium supplementation to bind the oxalate in the
bowel can prevent excessive urinary oxalate excretion
and thus lower the chance of developing calcium oxalate
stones. Sometimes Cholestyramine, potassium citrate, magnesium,
Vitamin B6 are also used.
Uric Acid Stones
Patients with Uric acid stones are advised to stay on
low protein diets to reduce acid ash (sulfur) and to reduce
purines that breakdown into uric acid. Alkalinization
of the urine with potassium citrate to keep the urine
pH between 6.5 and 7.5 is optimal. This urine pH can be
checked by the patient with the use of nitrazine paper.
Diamox (Acetazolamide) may be given at night to keep urine
alkaline. Sometimes Allopurinol is given if urinary uric
acid remains high.
Cystine Stones
With cystine
stones, urine output needs to be about 3 quarts
per day. Potassium citrate is used to alkalinize the urine
to pH 7-7.5. Patients are advised to decrease purines and
sodium. If urinary cystine is very high, patients are placed
on D-penicillamine or Thiola.
