Chemical shift magnetic resonance imaging could predict subclinical cortisol production from an incidentally discovered adrenal mass.

CONTEXT: To investigate whether any association between chemical shift magnetic resonance (MRI) findings, cortisol secretion and pathological findings exists that could predict subclinical hypercortisolism (SCH) in patients with adrenal incidentalomas (AI).

DESIGN: Retrospective, cross-sectional study in a tertiary centre.

PATIENTS: Sixty-eight subjects with AIs and 13 patients with Cushing's syndrome (CS). Patients with AIs were categorized according to cortisol levels post 1 mg dexamethasone (post-DST).

MEASUREMENTS: Visual inspection of the lipid content of the adrenal tumour and calculation of adrenal-to-spleen ratio (ASR), the signal intensity index (SII), volume and the assessment of the association between pathological, radiological and hormonal findings in surgically treated patients.

RESULTS: Percentage of clear cells was correlated with ASR (r = -.525, P = .01), SII (r = .465, P = .025), post-DST cortisol (r = -.711, P < .001) and ACTH (r = .475, P = .046). By ANOVA and post hoc analysis, patients with CS and five subjects with a post-DST cortisol greater than 137 nmol/L differed significantly in ASR and SII from those with a post-DST cortisol less than 50 nmol/L. An ASR level higher than 0.245 (OR 19.7, 95% CI 1.5-257.5; P = .023) and a SII level lower than 78.37 (OR 15.6, 95% CI 1.2-20; P = .034) remained as the independent predictors for SCH while age, presence of arterial hypertension or tumour volume did not make significant contribution to the models.

CONCLUSIONS: Cortisol hypersecretion by adrenal adenomas is associated with distinctive MRI characteristics. The quantitative assessment of intracellular lipid in an AI could help distinguish patients with a clear phenotype of SCH.