There are several different types of kidney stones, but each of them can cause a lot of pain.
Kidney stones are
small chunks of solid material that can form in your kidneys, a pair of organs
that filter your blood.
The
"stones," which are usually yellow and brown, vary in size and shape.
For instance, some
may be jagged and as small as a grain of sand, while others may be lumpy and
the size of golf balls.
A stone may stay in
the kidney or travel down the urinary tract — the body's waste and excess-water
drainage system — and get stuck, causing severe pain in the belly or side of
the back.
Other symptoms may
include nausea, chills, and blood in the urine.
Prevalence and Demographics of Kidney Stones
Kidney stones are
one of the most common disorders of the urinary tract, resulting in more than a
million visits to health care providers and 300,000 emergency room visits each
year in the United States, according to the National Institute of Diabetes and
Digestive and Kidney Diseases (NIDDK).
Kidney stones
affect both men and women, though struvite stones are more common in women and
uric acid stones are more common in men.
Overall, however,
the prevalence of kidney stones is higher in men than women.
Kidney stones are
also more common in obese people than non-obese people, and less common in
non-Hispanic African and Mexican-Americans than in non-Hispanic Caucasians,
according to the European Urology study.
What Are the Kidneys?
Part of the urinary
system, your two kidneys are fist-sized, bean-shaped organs, located just below
the rib cage, one on each side of the spine.
They have a number
of important functions, mainly filtering the blood to remove waste and excess
water, resulting in the formation of urine, which is stored in the bladder and
emptied from the body through the urethra.
The kidneys also:
- Balance
the body's levels of electrolytes, including sodium, potassium, and
phosphate, to maintain the body's balance of acids and bases
- Produce
hormones involved in regulating blood pressure, producing red blood cells,
and maintaining bone strength
- Prevent
the build up of waste and fluid in the body
Development of Kidney Stones
Kidney stones
develop when the concentration of normal kidney substances (especially calcium,
oxalate, and phosphorus) increases substantially.
This process —
sometimes known as nephrolithiasis — can be due to various factors, including
low fluid intake, diet, or medications such as diuretics and
calcium-based antacids.
A number of issues
can increase a person's risk of developing kidney stones, including:
- A
family history of kidney stones
- Medical
conditions that affect the levels of urinary substances
- Urinary
tract blockage
- Digestive
problems
- Recurrent urinary tract infections
Types of Kidney Stones
There are four main
types of kidney stones: calcium, uric acid, struvite, and cystine stones.
Calcium stones, of
which there are two forms — calcium oxalate and calcium phosphate — are the
most common type of kidney stone.
In most cases,
calcium oxalate stones form from high levels of calcium and oxalate in urine.
But if there are
high levels of urine calcium and the urine is alkaline (has a high pH), calcium
phosphate stones may form instead.
Uric acid stones
develop from overly acidic (low pH) urine.
This can result
from a diet high in purines, substances that are broken down to form uric acid
and are found in high concentrations in animal protein.
Struvite stones,
sometimes called infection stones, are made of magnesium, ammonium, and
phosphate, and typically form in alkaline urine.
They develop from
upper urinary tract infections, including kidney infections, when bacteria
produce urease, an enzyme that helps convert urea (a compound in urine) into
ammonia and other products.
Cystine stones
result from a genetic disorder that causes cystine, an amino acid, to leak into
the urine from the kidneys.
