Kidney Stone Analysis
Test OverviewKidney stone analysis is a test done on a
kidney stone to see what chemicals are in it. The test
is done on a kidney stone that has been passed in the urine or removed from the
urinary tract during surgery. Chemical analysis of a
kidney stone shows the
type of stone which can guide treatment and give
information that may prevent more stones from forming. People who have had a
kidney stone have a chance of having another one, so prevention measures are
important. A kidney stone (renal calculus) forms in the kidney
from substances that would normally pass out of the body in the urine. When there are large amounts of these substances, they separate from the urine and form kidney stones. A kidney stone can be as small as a grain of sand or as large as a golf ball. Sometimes a stone may leave the kidney and move down a
ureter into the
bladder. From the bladder, the stone passes through
the
urethra and out of the body in urine. Passing a kidney stone through a ureter
or the urethra may be painless or it may cause severe pain. A kidney stone may
cause other symptoms, such as blood in the urine (hematuria), pain when
urinating, or a severe need to urinate. Why It Is DoneA kidney stone analysis is done
to: - Find the chemical makeup of a kidney stone.
- Guide treatment for a kidney stone.
- Give information on how to prevent more kidney stones from
forming.
How To PrepareIf you think you might have a kidney
stone, talk to your doctor. He or she may have you collect the stone by
straining your urine through a fine-mesh strainer or through fine gauze. Your
doctor may give you a kidney stone strainer, or you may buy one from a drug
store. Straining the first urine specimen of the morning is important, because
a stone may pass into your bladder during the night. Look
carefully at the strainer for a kidney stone. It may look like a grain of sand
or a small piece of gravel. Any stone you find should be kept dry-do not put it
in fluid or urine. Put it in a cup with a lid or a plastic bag. Take it to the
doctor's office or lab for analysis. Do not put tape on the kidney stone
because it can change the test results. Talk to your doctor about any concerns you have regarding the need for the test, its
risks, how it will be done, or what the results will mean. To help you
understand the importance of this test, fill out the
medical test information form(What is a PDF document?). How It Is DoneThe kidney stone you take to the lab
will be cleaned of any blood or tissue and then looked at to find what
chemicals it is made of. How It FeelsThe most common way a kidney stone is
collected for this test is by passing it in urine. Passing a stone may be
painless or it may be very painful. The pain can begin suddenly and may come
and go. A sand-sized stone may pass with little pain. A larger stone may cause
a lot of pain in the lower back, groin, or genitals as it moves down the
ureters or the urethra. A small stone may pass without medical
treatment. A large stone may need surgery or another type of procedure to get
it out. RisksThere is no chance for problems with kidney stone
analysis. But a kidney stone can: - Have bacteria that can cause a
urinary tract infection (UTI).
- Damage the kidney, especially if the stone is a staghorn
(struvite) stone.
- Block the urinary tract. This can happen while the stone is
passing through the tract.
ResultsKidney stone analysis is a test done on a
kidney stone to see what chemicals are in it. Knowing the type of kidney stone helps guide the best treatment choice.
Your doctor will talk with you about treatment and prevention measures. - About 80% of kidney stones are made of calcium oxalate, calcium
phosphate, or a combination of both.footnote 1
- About 10% to 15% of kidney stones are made of magnesium ammonium
phosphate (struvite).footnote 1
- About 5% to 10% of kidney stones are made of uric acid.footnote 1
- Less than 1% of kidney stones are made of a chemical called
cystine.footnote 1
What Affects the TestPutting tape on a kidney stone to
keep it safe on the way to the lab may cause a problem with the test
results. What To Think About- About 80% of kidney stones in the ureters can be seen on an
X-ray.
- A
computed tomography (CT) scan of the
ureters and kidneys (also called a CT urogram) is one way to find kidney stones. To learn more, see the topic
CT Scan of the Body.
- Ultrasound may also be used to find kidney stones. To learn more, see the topic
Abdominal Ultrasound.
- Another test that can be done to find a kidney stone is
intravenous pyelogram (IVP). During IVP, a dye is put
into a vein in your arm. As the dye moves to the kidneys, X-rays are taken to
watch the movement of the dye and see where a stone may be. To learn more, see the topic
Intravenous Pyelogram (IVP).
- Most kidney stones have calcium in them. A low-calcium diet does
not often prevent stones from forming. To learn more about lowering your
chance for a kidney stone, see the topic
Kidney Stones.
- Knowing the type of kidney stone helps guide the best treatment
choice.
ReferencesCitations- Parmar MS (2004). Kidney stones. BMJ, 328(7453): 1420-1424.
Other Works Consulted- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
- Smith-Bindman R, et al. (2014). Ultrasonography versus computer tomography for suspected nephrolithiasis. New England Journal of Medicine, 371(12): 1100-1110. DOI: 10.1056/NEJMoa1404446. Accessed November 17, 2014.
CreditsByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
Specialist Medical ReviewerChristopher G. Wood, MD, FACS - Urology, Oncology Current as of:
May 3, 2017 Parmar MS (2004). Kidney stones. BMJ, 328(7453): 1420-1424. Last modified on: 8 September 2017
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