# Segmental Adrenal Venous Sampling in Unilateral Primary Aldosteronism With Apparent Bilateral Aldosterone Suppression

## TL;DR

This case study shows how a specialized blood sampling technique can accurately diagnose a rare form of high blood pressure hidden by misleading test results.

## Contribution

The study introduces the use of super-selective adrenal venous sampling to identify unilateral aldosterone-producing adenoma in cases of apparent bilateral suppression.

## Key findings

- Apparent bilateral suppression can be caused by anatomical factors like aldosterone dilution from non-APA areas.
- Super-selective AVS can pinpoint aldosterone hypersecretion regions, enabling accurate diagnosis of unilateral PA.
- A right adrenal nodule was identified as the source of aldosterone in a patient with ABAS.

## Abstract

Apparent bilateral adrenal suppression (ABAS), where aldosterone/cortisol ratios in both adrenal veins are lower than in the inferior vena cava, yields uninterpretable adrenal venous sampling (AVS) results and is poorly understood. A 57-year-old male with hypertension and spontaneous hypokalemia was admitted to our hospital. Confirmatory tests established a diagnosis of primary aldosteronism (PA). Initial AVS indicated ABAS, but unilateral PA remained possible due to elevated aldosterone, low renin, hypokalemia, and a right adrenal nodule (8 × 7 mm) on computed tomography. Subsequently, a second, super-selective AVS identified tributaries from areas of aldosterone hypersecretion, enabling accurate localization of unilateral PA. ABAS may occur due to anatomical factors such as dilution by tributaries from nonaldosterone-producing adenoma (APA) areas with suppressed aldosterone production. Super-selective AVS proves beneficial in diagnosing unilateral PA concealed within ABAS by pinpointing tributaries from APA regions.