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Urine concentration test
Water loading test; Water deprivation test
A urine concentration test measures the ability of the kidneys to conserve or excrete water.
How the Test is Performed
For this test, the specific gravity of urine , urine electrolytes , and/or urine osmolality are measured before and after one or more of the following:
Specific gravity of urine
Urine specific gravity is a laboratory test that shows the concentration of all chemical particles in the urine.
Urine electrolytes
The electrolytes - urine test measures specific chemicals called electrolytes in urine. It usually measures the levels of calcium, chloride, potassi...
Urine osmolality
The osmolality urine test measures the concentration of particles in urine. Osmolality can also be measured using a blood test.
- Water loading. Drinking large amounts of water or receiving fluids through a vein.
- Water deprivation. Not drinking fluids for a certain amount of time.
- ADH administration. Receiving antidiuretic hormone (ADH), which should cause the urine to become concentrated.
After you provide a urine sample, it is tested right away. For urine specific gravity, the health care provider uses a dipstick made with a color-sensitive pad. The dipstick color changes and tells the provider the specific gravity of your urine. The dipstick test gives only a rough result. For a more accurate specific gravity result or measurement of urine electrolytes or osmolality, your provider will send your urine sample to a lab.
If needed, your provider may ask you to collect your urine at home over 24 hours . Your provider will tell you how to do this. Follow instructions exactly so that the results are accurate.
Collect your urine at home over 24 hour
The urine 24-hour volume test measures the amount of urine produced in a day. The amount of creatinine, protein, and other chemicals released into t...
How to Prepare for the Test
Eat a normal, balanced diet for several days before the test. Your provider will give you instructions for water loading or water deprivation.
Your provider will ask you to temporarily stop any medicines that may affect the test results. Be sure to tell your provider about all the medicines you take, including dextran and sucrose. DO NOT stop taking any medicine before talking to your provider.
Also tell your provider if you recently received intravenous dye (contrast medium) for an x-ray. The dye can also affect test results.
How the Test will Feel
The test involves only normal urination. There is no discomfort.
Why the Test is Performed
This test is most often done if your doctor suspects central diabetes insipidus . The test can help tell that disease from nephrogenic diabetes insipidus .
Central diabetes insipidus
Central diabetes insipidus is a rare condition that involves extreme thirst and excessive urination.
Nephrogenic diabetes insipidus
Nephrogenic diabetes insipidus (NDI) is a disorder in which a defect in the small tubes (tubules) in the kidneys causes a person to pass a large amou...
This test may also be done if you have signs of syndrome of inappropriate ADH (SIADH).
Syndrome of inappropriate ADH
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH). This ho...
Normal Results
In general, normal values for specific gravity are as follows:
- 1.000 to 1.030 (normal specific gravity)
- 1.001 after drinking excessive amounts of water
- More than 1.030 after avoiding fluids
- Concentrated after receiving ADH
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
Increased urine concentration may be due to different conditions, such as:
-
Heart failure
Heart failure
Heart failure is a condition in which the heart is no longer able to pump oxygen-rich blood to the rest of the body efficiently. This causes symptom...
ImageRead Article Now Book Mark Article - Loss of body fluids (dehydration) from diarrhea or excessive sweating
- Narrowing of the kidney artery (renal arterial stenosis)
- Sugar, or glucose, in the urine
-
Syndrome of inappropriate antidiuretic hormone secretion (
SIADH
)
SIADH
Low sodium level is a condition in which the amount of sodium (salt) in the blood is lower than normal. The medical name of this condition is hypona...
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Decreased urine concentration may indicate:
- Diabetes insipidus
- Drinking too much fluid
-
Kidney failure
(loss of ability to reabsorb water)
Kidney failure
Acute kidney failure is the rapid (less than 2 days) loss of your kidneys' ability to remove waste and help balance fluids and electrolytes in your b...
ImageRead Article Now Book Mark Article - Severe kidney infection (pyelonephritis)
Risks
There are no risks with this test.
References
Ferri FF. Diabetes insipidus. In: Ferri FF, ed. Ferri's Clinical Advisor 2016 . Philadelphia, PA: Elsevier Mosby; 2016:409.e2-409.e.
Inker LA, Fan L, Levey AS. Assessment of renal function. In: Johnson RJ, Feehally J, Floege J. Comprehensive Clinical Nephrology . 5th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 3.
McPherson RA, Ben-Ezra J. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods . 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 28.
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Urine concentration test - illustration
The urine concentration test is a test that measures whether the kidneys are conserving or excreting water properly. A sample of urine is retrieved and tested for its specific gravity.
Urine concentration test
illustration
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Female urinary tract - illustration
The female and male urinary tracts are relatively the same except for the length of the urethra.
Female urinary tract
illustration
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Male urinary tract - illustration
The male and female urinary tracts are relatively the same except for the length of the urethra.
Male urinary tract
illustration
-
Urine concentration test - illustration
The urine concentration test is a test that measures whether the kidneys are conserving or excreting water properly. A sample of urine is retrieved and tested for its specific gravity.
Urine concentration test
illustration
-
Female urinary tract - illustration
The female and male urinary tracts are relatively the same except for the length of the urethra.
Female urinary tract
illustration
-
Male urinary tract - illustration
The male and female urinary tracts are relatively the same except for the length of the urethra.
Male urinary tract
illustration
-
Kidney stones
(In-Depth)
Review Date: 8/29/2015
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
