Tests and diagnosis

By Mayo Clinic Staff

A variety of tests are available to help diagnose primary aldosteronism.

Screening test

Initially, your doctor is likely to measure the levels of aldosterone and renin in your blood. Renin is an enzyme released by your kidneys that helps regulate blood pressure. The combination of a very low renin level with a high aldosterone level suggests that primary aldosteronism may be the cause of your high blood pressure.

Confirmation tests

If the aldosterone-renin test suggests that you might have primary aldosteronism, you'll need another test to confirm the diagnosis, such as one of the following:

  • Oral salt loading. You'll follow a high-sodium diet for three days before your doctor measures aldosterone and sodium levels in your urine.
  • Saline loading. Your aldosterone levels are tested after sodium mixed with water (saline) is infused into your bloodstream for several hours.
  • Fludrocortisone suppression test (FST). After you've followed a high-sodium diet and taken fludrocortisone — which mimics the action of aldosterone — for several days, aldosterone levels in your blood are measured.

Additional tests

If you receive a diagnosis of primary aldosteronism, your doctor will run additional tests to determine whether the underlying cause is an aldosterone-producing adenoma or overactivity of both adrenal glands. Tests may include:

  • Abdominal computerized tomography (CT) scan. A CT scan can help identify a tumor on your adrenal gland or an enlargement that suggests overactivity. You may still need additional testing after a CT scan because this imaging test may miss small but important abnormalities or find tumors that don't produce aldosterone.
  • Adrenal vein sampling. A radiologist draws blood from both your right and left adrenal veins and compares the two samples. Aldosterone levels that are significantly higher on one side indicate the presence of an aldosteronoma on that side. Similar aldosterone levels on both sides point to overactivity in both glands.

    This test involves placing a tube in a vein in your groin and threading it up to the adrenal veins. Though essential for determining the appropriate treatment, this test carries the risk of bleeding or a blood clot in the vein.

Jan. 02, 2014

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