24-hour urinary aldosterone excretion rate

Alternative names 
Aldosterone - urine

Definition
24-hour urinary aldosterone excretion rate test measures the amount of aldosterone eliminated in the urine in a day.

How the test is performed
A 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

     
  • On day 1, urinate into the toilet when you get up in the morning.  
  • Afterwards, collect all urine in a special container for the next 24 hours.  
  • On day 2, urinate into the container when you get up in the morning.  
  • 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.

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 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. Diaper as usual over the secured bag.

This procedure may take a couple of attempts - lively infants can displace the bag, causing the specimen to be absorbed by the diaper. 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.

Deliver it to the laboratory or your health care provider as soon as possible upon completion. The lab analyzes the sample for the amount of aldosterone.

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.

How the test will feel
The test involves only normal urination, and there is no discomfort.

Why the test is performed
The test evaluates the excretion of aldosterone in the urine. Aldosterone is a hormone secreted by the adrenal gland which acts on the kidney to regulate salt and potassium balance.

Normal Values
Normal values range from 6 to 25 mcg/24 hours. (This depends on the amount of sodium excreted by the body. The greater the amount of sodium, the lower the level of aldosterone.) Normal value ranges may vary slightly among different laboratories.

Note: mcg/24 hr = micrograms per 24 hours

What abnormal results mean
Greater than normal levels of aldosterone may indicate:

     
  • Conn’s syndrome (aldosterone-secreting adenoma)  
  • Bilateral adrenal hyperplasia  
  • Primary aldosteronism  
  • Secondary aldosteronism due to a variety of causes including:       o Diuretic abuse       o Laxative abuse       o Cirrhosis       o Heart failure

Lower than normal levels may indicate Addison’s disease

What the risks are
There are no risks.

Special considerations
The results may be questionable, if the renal function is not normal.

Nonpharmacological factors that can affect aldosterone measurements include: strenuous exercise, acute stress, high- or low-sodium diet, and pregnancy.

Drugs that can increase aldosterone measurements include: lithium, spironolactone, and verapamil.

Drugs that can decrease aldosterone measurements include: ACE inhibitors, NSAIDS, ranitidine, and propranolol.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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