Urine concentration test

20 Jun

Posted by admin as Uncategorized

A urine concentration test measures the ability of the kidneys to conserve or excrete water appropriately.

Alternative names

Water loading test; Water deprivation test

How the Test is Performed?

For this test, the specific gravity of urine is measured before and after one or more of the following: Water loadingdrinking excessive amounts of water or receiving fluids through a vein, Water deprivation avoiding fluids for a certain amount of time, ADH adminitration receiving antidiuretic hormone (ADH), which should cause the urine to become concentrated.The test requires a clean-catch urine sample.To obtain a clean-catch sample, men or boys should clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well.

For infants, thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For boys, the entire penis can be placed in the bag and the adhesive attached to the skin. For girls, the bag is placed over the labia. Diaper as usual over the secured bag. This procedure may take a couple of attempts — lively infants can displace the bag. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

How to Prepare for the Test?

Eat a normal, balanced diet for several days before the test. Your health care provider will give you instructions for water loading or water deprivation.Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. Drugs that can affect measurements include dextran and sucrose, and x-ray contrast medium (dye) received within 3 days.

Why the test is performed?

Most often, a urine concentration test is performed when diabetes insipidus is suspected and to help differentiate it from nephrogenic diabetes insipidus. SIADH (syndrome of inappropriate ADH ) — a condition where urine concentrations are excessively high (water is conserved) given the person’s degree of hydration — is another condition where urine concentration values are helpful for diagnostic and therapeutic purposes. Normally, the kidneys regulate the concentration of urine by adjusting the excretion of water. Water excretion is regulated, in part, by ADH (anti-diuretic hormone).

Normal Values

Normal values are indicated as follows (normal value ranges may vary slightly among different laboratories):1.010 to 1.025 (normal specific gravity) , 1.001 after water loading More than 1.025 after water deprivation, Concentrated (increased specific gravity) after ADH administration.

How the test will feel?

The test involves only normal urination, and there is no discomfort.

Special considerations

Drugs that can increase specific gravity measurements include dextran and sucrose, and radiographic contrast medium within 3 days

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