Hyperaldosteronism can be diagnosed through various diagnostic tests, including:

Blood tests: Measuring aldosterone and renin levels in the blood, as well as calculating the aldosterone-to-renin ratio.

Imaging studies: Such as computed tomography (CT) or magnetic resonance imaging (MRI) scans to detect any adrenal abnormalities.

Adrenal vein sampling: A procedure to sample blood from the adrenal veins to compare aldosterone levels on each side, aiding in the localization of the source of excess aldosterone.

Aldosteronoma, also known as primary aldosteronism or Conn's syndrome, refers to the presence of an adrenal adenoma (benign tumor) causing excessive aldosterone production. 

Aldosterone-to-renin ratio: Elevated levels suggest primary aldosteronism and may warrant further investigation.

Imaging studies: CT or MRI scans are used to identify the presence of an adrenal tumor.

Confirmatory tests: Additional tests, such as saline infusion test or oral salt loading, may be conducted to confirm aldosterone excess and evaluate the response.

Hyperaldosteronism can have several differential diagnoses, including:

Renin-Independent Causes: Conditions where aldosterone production is not influenced by renin, such as glucocorticoid-remediable aldosteronism (GRA), Liddle syndrome, or apparent mineralocorticoid excess (AME).

Secondary Hyperaldosteronism: Conditions where increased aldosterone production occurs as a result of excessive renin secretion due to factors like renal artery stenosis, heart failure, or cirrhosis.

Medications and Lifestyle: Certain medications (e.g., diuretics) and excessive licorice consumption can mimic hyperaldosteronism.

The gold standard test for hyperaldosteronism is considered to be adrenal vein sampling (also known as adrenal venous sampling or AVS). AVS involves sampling blood from both adrenal veins to measure aldosterone levels, allowing for the differentiation between unilateral (one-sided) and bilateral (both sides) aldosterone excess. It helps guide treatment decisions, as unilateral cases (typically due to aldosteronoma) are amenable to surgical intervention, while bilateral cases often require medical management. AVS should be performed by an experienced interventional radiologist or endocrinologist in specialized centers.

Reference: