24-hour urinary aldosterone excretion rate

Definition

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

See also: Blood aldosterone test

Alternative Names

Aldosterone - 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 may tell you to stop taking 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.

Other factors that can affect aldosterone measurements include:

• Pregnancy
• High- or low-sodium diet
• Strenuous exercise
• Stress

Avoid coffee, tea, and cola during urine collection. Your health care provider will usually recommend that you eat no more than 3 grams of salt (sodium) per day for at least 2 weeks before the test.

How the Test Will Feel

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

Why the Test is Performed

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

Normal Results

Results depend on:

• How much sodium is in your diet
• Whether your kidneys work properly
• The condition being diagnosed

Normal values vary from lab to lab. Talk to your doctor about your specific test results.

What Abnormal Results Mean

Greater than normal levels of aldosterone may be due to:

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

Lower than normal levels may indicate Addison's disease.

Risks

There are no risks.

References

Young Jr WF. Endocrine hypertension. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 16.

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