24-hour urinary aldosterone excretion rate

Definition

The 24-hour urinary aldosterone excretion rate test measures the amount of aldosterone eliminated in the urine in a day. Aldosterone is a hormone released by the adrenal gland that helps the kidney to control salt and potassium balance.

See also: Blood aldosterone test

Alternative Names

Why the Test is Performed

The test is done to see how much aldosterone is released into your urine.

How the Test is Performed

A 24-hour urine sample is needed.

• 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 an 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 the infant. For males, place the entire penis in the bag and attach the adhesive to the skin. For females, place the bag over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can move the bag, causing the urine to be absorbed by the diaper. Check the infant frequently and change the bag after the infant has urinated into it. Drain the urine from the bag into the container provided by your health care provider.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to Prepare for the Test

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

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

Drugs that can decrease aldosterone measurements include ACE inhibitors, nonsteroidal anti-inflammatory drugs, ranitidine, and propranolol.

Factors, other than medications, that can affect aldosterone measurements include strenuous exercise, acute stress, high- or low-sodium diet, and pregnancy. You should avoid coffee, tea, and cola during urine collection. Remain on a 3 gram of sodium per day diet for at least 2 weeks.

How the Test Will Feel

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

Risks

There are no risks.

Normal Results

Normal values range from 1.5 to 85 micrograms per 24 hours. However, results depend on the amount of sodium in your diet. The greater the amount of dietary sodium, the lower the level of aldosterone.

Results may be questionable if your kidneys do not function properly.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Greater-than-normal levels of aldosterone may be due to:

• Conn's syndrome
• Bilateral adrenal hyperplasia
• Abuse of diuretics ("water pills")
• Laxative abuse
• Cirrhosis
• Heart failure

Lower than normal levels may indicate Addison's disease.