Bioimpedance spectroscopy uncovers extracellular fluid excess in primary aldosteronism.

OBJECTIVE

Primary aldosteronism is a common but underdiagnosed cause of secondary hypertension, characterized by volume overload. Bioimpedance spectroscopy is widely used to assess fluid status in dialysis patients. We examined whether this method can distinguish primary aldosteronism from essential hypertension (EH).

DESIGN

Patients with confirmed primary aldosteronism (n = 77), EH (n = 90), and normotensive controls (n = 79) were prospectively recruited for a cross-sectional comparison.

METHODS

Total body water, extracellular and intracellular water, and overhydration were measured using bioimpedance spectroscopy. Analyses were adjusted for sex, age, body surface area, estimated glomerular filtration rate, diuretic or spironolactone use, and comorbid diabetes or heart failure. Routine laboratory and hormonal tests were performed.

RESULTS

Extracellular water (ECW) volume was 0.69 ± 1.04 and 0.88 ± 1.04 L/m2 higher, and overhydration 0.76 ± 1.4 and 0.92 ± 1.4 L greater, in primary aldosteronism than in EH and normotensive controls, respectively (P < .001 for all). Total body water did not differ significantly among groups (21.3 ± 2.2, 21.0 ± 2.8, and 21.6 ± 2.4 L/m2, respectively; P = .083). Plasma N-terminal pro-atrial natriuretic peptide concentration was highest in primary aldosteronism. Primary aldosteronism severity correlated positively with ECW volume (rS = 0.31), overhydration (rS = 0.43), and extracellular-to-intracellular water ratio (rS = 0.36; P < .01 for all).

CONCLUSION

ECW overload in primary aldosteronism can be assessed using bioimpedance spectroscopy. Further research should determine whether addition of this method to current approaches can improve diagnostic accuracy for primary aldosteronism.