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 (see also the blood aldosterone test).

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

Avoid coffee, tea, and cola during urine collection. Stop diuretics. Use antihypertensive drugs and birth control pills as instructed by your physician. Avoid excess stress (emotional or physical), and remain on a 3 gram of sodium per day diet for at least two weeks.

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 1.5 to 85 mcg/24 hours. This depends on the amount of sodium a person takes in. The greater the amount of dietary 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 (primary aldosteronism, most often due to an aldosterone-secreting benign tumor)
• Bilateral adrenal hyperplasia
• Secondary aldosteronism due to a variety of causes including:
  • Diuretic ("water pill") abuse
  • Laxative abuse
  • Cirrhosis
  • Heart failure

What the risks are

There are no risks.

Special considerations

Results may be questionable if  renal function is not normal.

Factors, other than medications, 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.

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Aldosterone - urine