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Kidney Stones Introduction |
The medical term for
kidney stones is
nephrolithiasis. [1] The actual stone is referred to as a
calculus or calculi (plural). There
are many different types of calculi,
however the majority (75%) are
composed of calcium. [2] Kidney stones can occur in any place
along the urinary tract and lead to
symptomatic pain, also known as
renal colic. Depending on the type
of stone, the specific pathogenesis
may vary. For example, a uric acid
stone is the result of increased
urine acidity which crystallizes undissociated uric acid, while
magnesium ammonium phosphate calculi
indicate a urinary tract infection
caused by a specific type of
bacteria. [1] However, a common feature is that
the urine contains a high amount of
specific salts that allow stones to
form. As well, patients often have
abnormalities of crystal growth
inhibitors (pyrophosphate, citrate, and glycosaminoglycans) and
preformed nuclei for the stones to
form. [1,
2] It can be said that a
variety of factors must be present
for calculi to form. Patients
can have urine saturated with the
aforementioned
salts, but not result in stone
formation.
The types of
kidney stones can be divided
into four main categories: calcium-containing
stones, triple or struvite
stones (magnesium ammonium
phospahate), uric acid stones and cystine
stones. [2] Calcium containing stones, as
mentioned above, account for the
vast majority of cases. Most of
these stones are made up of calcium
oxalate and are due to increased
calcium in the urine. Fifty percent
of these patients have idiopathic hypercalcuria, which refers to an
abnormally high amount of calcium in
the urine. [2] This condition is hereditary,
and far more common in women.
Hyperoxaluria,
or high oxalates in the urine, is
responsible for about five percent,
of calcium oxalate stones. [2] This is
largely due to disorders of
the digestive tract, which allow
excess oxalate absorption, or by
consuming massive amounts of oxalate
containing foods such as rhubarb,
spinach, or nuts. A few of these
patients have a primary/underlying disorder
that directly leads to hyperoxaluria.
Patients with
kidney stones generally
present pain in the mid to low
back, which can be due to a blockage
in the renal system caused by a
kidney stone. [1] This pain has a particular pattern
and is referred to as renal colic. The lining of the ureter (the tube
that connects the kidney to the
bladder) is irritated causing
increased frequency and force of
peristaltic movement of urine, which
results in the colicky pain seen in
these patients. [4] Typically, a patient will experience
episodes of intermittent extreme
pain across the flank region, which
may extend across the abdomen. Depending on where the stone has
lodged, there may be pain very low
in the abdomen, or just above the pubic
bone if a stone has reached the
bladder.
Blood in the urine (hematuria)
can be a sign of kidney stones. Other symptoms include nausea,
vomiting, distention of the abdomen,
chills, fever, and polyuria (frequent
urination). A patient can also
appear very agitated due to the
colicky pattern of pain.
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Approximately 1 in
1000 Americans present in hospital
due to kidney stones. [1]
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The incidence of
nephrolithiasis is increasing in
the Western world and is proposed
to be a disease of lifestyle, just
like heart disease.
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Kidney stones
occur more commonly in males, and
the National Institutes of Health
cite that 80% of cases are seen in
the male population. [2]
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Kidney Stones |
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