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Adrenal Incidentaloma (ACR)

Guided recommendation from the ACR Incidental Adrenal Mass white paper (Mayo-Smith et al., JACR 2017, Fig 1). Answer the questions; an optional paste box pre-selects what it can.

→ Adrenal Nodule Evaluation (HU / washout / chemical-shift / PET calculators)

For adults (≥18 y), asymptomatic, imaged for an unrelated reason. Bilateral masses: assess each separately. Consider biochemical evaluation for most incidental adrenal masses, and exclude pheochromocytoma before any biopsy or resection.

Encodes the ACR Incidental Adrenal Mass algorithm (Fig 1). Not for known adrenal disease or biochemically suspected hyperfunction. Recommendations, not standard of care: deviate as the imaging and patient warrant.

Parses size and a few keywords (fat/myelolipoma, lipid/≤10 HU, cyst/no enhancement, calcification, stable, enlarging, cancer/metastasis) to pre-select below — always review.

ACR adrenal algorithm — key thresholds & definitions

Diagnostic benign features (stop, regardless of size)

Macroscopic fat = myelolipoma. No enhancement (<10 HU change between unenhanced and enhanced CT) = cyst or hemorrhage. Benign-pattern calcification (old hematoma, granulomatous). ≤10 HU on unenhanced CT, or signal drop on chemical-shift MRI = lipid-rich adenoma.

Subcentimeter

A mass <1 cm in short axis need not be pursued.

Indeterminate, ≥1 to <4 cm

Prior imaging stable ≥1 year → benign. New/enlarging → no cancer Hx: biochemical workup ± follow-up adrenal CT or resection (possible adrenal cortical carcinoma); cancer Hx: biopsy or PET-CT. No prior, no cancer Hx: 1–2 cm probably benign, consider 12-month follow-up adrenal CT; >2–<4 cm: dedicated adrenal CT. Newer evidence: Corwin et al. (AJR 2026; 12 institutions, 1,506 nodules, no cancer history) found 0/773 malignant at 1–2 cm and 1/694 at 2–4 cm, supporting no follow-up for 1–2 cm nodules. The single cancer was an ACC that grew from 2.7 to 4.1 cm over 9 years. No prior, cancer Hx & isolated mass: dedicated adrenal CT.

Indeterminate, ≥4 cm

No cancer Hx → consider resection (possible primary adrenal cortical carcinoma). Cancer Hx → consider biopsy or PET-CT (presumed metastasis).

Dedicated adrenal CT (washout)

Reduced-dose unenhanced ≤10 HU = benign adenoma. >10 HU → washout: no enhancement (<10 HU change) = cyst/hemorrhage (benign); APW ≥60% or RPW ≥40% = benign adenoma; APW <60% / RPW <40% = indeterminate (imaging follow-up, biopsy, PET-CT, or resection per clinical scenario). APW = (enhanced − 15-min delayed)/(enhanced − unenhanced) × 100%. RPW = (enhanced − 15-min delayed)/enhanced × 100%.

Mayo-Smith WW, et al. Management of Incidental Adrenal Masses: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol 2017;14:1038–1044 (algorithm, Fig 1).