Kidney Stones
Description
- A kidney stone is a calculus or a crystalline mass that has formed in the pelvis
of the kidney. Kidney stones are composed principally of urates, oxalates, phosphates,
and carbonates, and can be up to an inch or more in diameter
Causes
- Dehydration may lead to more concentrated urine and the inability to remove all
calculus forming substances.
- Infection may lead to a build up of calculi. Bacteria or scar tissue may serve
as the nucleus of the kidney stone.2
- Acidic (low pH) urine may provide an environment conducive to kidney stone formation.
- At one time it was believed that dietary calcium might cause kidney stones.3 However,
more recent studies indicate that dietary calcium actually decreases kidney stone
formation.4
Types
- Kidney stones are categorized by the minerals that they contain.
At Risk
- People who live in the southeastern United States are at higher risk. The reasons
for this increased geographic risk are not entirely understood, but dehydration
due to the higher temperatures may play a role, and regional dietary preferences
may also contribute.5
- Those who get kidney stones once are at a high risk of recurrence.
Prevention and Management
Nutritional Influences:
- Increasing dietary calcium may help reduce the occurrence of kidney stones.
- Magnesium may reduce the incidence of kidney stones by improving the ratio of
calcium to magnesium.6
- Vitamin B6 may reduce the incidence of oxalate containing kidney stones.7
- Increased consumption of fluids, particularly water, reduces the risk of stone
formation.
- Reducing intake of meat protein may also help.8
- There continues to be a debate about whether or not patients prone to kidney
stones should take more than 2,000 mg of vitamin C higher a day. A study published
in 1996 concluded that there was no correlation between taking large amounts of
vitamin C and the occurrence of kidney stones.9
Additional Information
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>Abstracts
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. PURPOSE:
The association between the intake of vitamins C and B6, and kidney stone formation
was examined. MATERIALS AND METHODS: We conducted a prospective study of the relationship
between the intake of vitamins C and B6 and the risk of symptomatic kidney stones
in a cohort of 45,251 men 40 to 75 years old with no history of kidney calculi.
Vitamin intake from foods and supplements was assessed using a semiquantitative
food frequency questionnaire completed in 1986. RESULTS: During 6 years of followup
751 incident cases of kidney stones were documented. Neither vitamin C nor vitamin
B6 intake was significantly associated with the risk of stone formation. For vitamin
C the age-adjusted relative risk for men consuming 1,500 mg. daily or more compared
to less than 250 mg. daily was 0.78 (95% confidence interval 0.54 to 1.11). For
vitamin B6 the age-adjusted relative risk for men consuming 40 mg. daily or more
compared to less than 3 mg. daily was 0.91 (95% confidence interval 0.64 to 1.31).
After adjusting for other potential stone risk factors the relative risks did not
change significantly. CONCLUSIONS: These data do not support an association between
a high daily intake of vitamin C or vitamin B6 and the risk of stone formation,
even when consumed in large doses.
Soucie JM, Coates RJ, McClellan W, Austin H, Thun M. Relation between geographic variability in kidney stones prevalence and risk factors for stones. Am J Epidemiol
1996 Mar 1;143(5):487-95. To determine whether geographic variability
in rates of kidney stones in the United States was attributable to differences
in personal and environmental exposures, the authors examined cross-sectional
data that included information on self-reported, physician-diagnosed kidney stones
collected from 1,167,009 men and women, aged > or = 30 years, recruited nationally
in 1982. Information on risk factors for stones including age, race, education,
body mass, hypertension, and diuretic and vitamin C supplement use was obtained
by self administered questionnaire. Consumption of milk, coffee, tea, soft drinks,
and alcohol was based on food frequency data. Indices of ambient temperature
and sunlight level were assigned to subjects based on state of residence. Stones
were nearly twice as prevalent in the Southeast as in the Northwest among men
and women. Ambient temperature and sunlight indices were independently associated
with stones prevalence after controlling for other risk factors for stones. Regional
variation was eliminated for men and greatly reduced for women after adjustment
for temperature, sunlight, and beverage consumption. Other factors appeared to
not contribute to regional variation. These results provide evidence that ambient
temperature and sunlight levels are important risk factors for stones and that
differences in exposure to temperature and sunlight and beverages may contribute
to geographic variability.
Jaeger P. Prevention of recurrent calcium stones: diet
versus drugs. Miner Electrolyte Metab 1994;20(6):410-3. Excessive intakes
of meat protein, oxalate and potentially sodium, as well as insufficient intakes
of vegetables fibers, calcium and fluid all lead to increased urinary crystallization.
Renal stone disease, however, does not have to ensue. The underlying condition
in a given patient is of paramount importance to allow 'bad eating habits' to
lead to nephrolithiasis. Several of these underlying abnormalities have been
detected so far from which we recently derived the powder keg and tinderbox theory.
Most of the time, the dietary approach to nephrolithiasis allows recurrence of
renal stone formation to be prevented. The pharmacological approach should be
reserved for refractory cases. Comparison of dietary calcium with supplemental
calcium and other nutrients as factors affecting the risk for kidney stones in
women
References
1 Tabers Cyclopedic Medical Dictionary. 16th ed. Philadelphia:F.A. Davis
Company;1985. P346.
2 Diseases. Springhouse (PA):Springhouse Corporation; 1993 p 50.
3 Diseases. 2nd ed. Springhouse (PA):Springhouse Corporation; 1993. p 898.
4 Jaeger P. Prevention of recurrent calcium stones: diet versus drugs. Miner
Electrolyte Metab 1994;20(6):410-3.
5 Diseases. 2nd ed. Springhouse (PA):Springhouse Corporation; 1993. p 893.
6 Somer, E. The Essential Guide to Vitamins and Minerals. New York:Harper
Perennial; 1992. p 204.
7 Somer E. The Essential Guide to Vitamins and Minerals. New York:HarperPerennial
1992. p 128-129
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
