What is the role of 24-hour urinary aldosterone (U-Aldo) excretion testing to confirm primary aldosteronism?

Updated: Mar 24, 2020
  • Author: Gabriel I Uwaifo, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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The 24-hour urinary aldosterone (U-Aldo) excretion test is one of the most useful confirmatory diagnostic tools because it is an index for total daily aldosterone secretion (in a fashion similar to the 24-h urinary free cortisol [UFC], which is typically elevated in patients with Cushing syndrome).

In most patients with primary aldosteronism, the 24-hour U-Aldo is greater than 14 mcg/day (after 3 days of salt loading). Only about 7% of patients with primary aldosteronism have values of less than 14 mcg/day.

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