| Subject | Contents |
| Definition | This test measures the amount of sodium in urine. |
| Alternative Names | Urinary 24 hours sodium; Urine Na+ |
| How the test is performed | Urine may be collected over a 24 hour period or by the "clean-catch" method. The urine is then analyzed by a laboratory. If a 24 hour urine sample is needed, your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. On day 1, urinate into the toilet upon arising in the morning. Collect all subsequent urine (in a special container) for the next 24 hours. On day 2, urinate into the container in the morning upon arising. Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed. Infant: 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 your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all). The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into the container for transport to the laboratory. Deliver it to the laboratory or your health care provider as soon as possible upon completion. Child or adult: Collect a "clean-catch" (midstream) urine sample. To obtain a clean-catch sample, men or boys should wipe 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. As you start to urinate, allow a small amount to fall into the toilet bowl (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant. |
| How to prepare for the test | No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary. The health care provider may advise you to discontinue drugs that can affect the test (see Special Considerations). |
| How the test will feel | The test involves only normal urination, and there is no discomfort. |
| Why the test is performed | The test is often used to determine hydration status and the kidney's ability to conserve or excrete sodium. This test may also be performed to indirectly indicate the function of the adrenal cortex or to detect or monitor conditions that result in abnormal urine sodium levels. Aldosterone (see the aldosterone test), a hormone produced by the adrenal gland, plays a major role in regulating sodium levels within the body and urine. Specifically, aldosterone increases the reabsorption of sodium in the kidneys at the expense of potassium and hydrogen loss. Reabsorption of sodium in turn enhances retention of water in body tissues and the blood stream. It is by this means that aldosterone helps maintain plasma volume and blood pressure. Dehydration and conditions that decrease kidney blood flow stimulate aldosterone production. |
| Normal Values | Normal values are generally 15 to 250 mEq/L/day, depending on hydration status and daily intake of dietary sodium. Note: mEq/L/day = milliequivalents per liter per day |
| What abnormal results mean | Greater-than-normal urine sodium levels may indicate: Adrenocortical insufficiency Steroid use Excessive salt intake Lower-than-normal urine sodium levels may indicate: AldosteronismCongestive heart failureDiarrhea and dehydration states Renal failure Additional conditions under which the test may be performed: Acute tubular necrosisHepatorenal syndromeMedullary cystic disease Glomerulonephritis Prerenal azotemia |
| What the risks are | There are no risks. |
| Special considerations | Deficient or excessive amounts of sodium (salt) in the diet may affect test results. Drugs that can increase test measurements include some antibiotics, diuretics, prostaglandins, and certain corticosteroids. Drugs that can decrease test measurements include NSAIDS. |
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