Imaging recommendation · Abdomen · Pelvis

Cushing's syndrome — imaging localization after biochemical confirmation

Q: What's the alternative imaging for cushing's syndrome — imaging localization after biochemical confirmation when acth-independent (adrenal cushing)?

CT — Adrenal CT with washout protocol or chemical-shift MRI (see adrenal-mass) (iv contrast).

Q: What's the alternative imaging for cushing's syndrome — imaging localization after biochemical confirmation when pituitary mri negative — acth-dependent cushing?

Inferior petrosal sinus sampling (IR procedure) (iv contrast).

Q: What's the alternative imaging for cushing's syndrome — imaging localization after biochemical confirmation when ectopic acth suspected?

NM — CT chest/abd/pelvis + Ga-68 DOTATATE PET-CT (occult NET) (iv contrast).

Q: What's the alternative imaging for cushing's syndrome — imaging localization after biochemical confirmation when bilateral adrenal hyperplasia (ppnad, aimah)?

MRI — Adrenal MRI for characterization (iv contrast).

Recommended: Pituitary MRI (ACTH-dependent) or adrenal CT (ACTH-independent) is the preferred imaging study for cushing's syndrome — imaging localization after biochemical confirmation. Imaging follows biochemical confirmation (low-dose dexamethasone suppression, midnight cortisol, ACTH).

Recommended study

Pituitary MRI (ACTH-dependent) or adrenal CT (ACTH-independent)

MRI IV contrast Preferred Abdomen · Pelvis Outpatient Reviewed 2026-05

Imaging follows biochemical confirmation (low-dose dexamethasone suppression, midnight cortisol, ACTH). ACTH-dependent (Cushing disease ~70%, ectopic ~10%): dedicated dynamic pituitary MRI with 1 mm sellar protocol. ACTH-independent (~20%): adrenal CT or MRI to characterize adenoma vs carcinoma vs bilateral hyperplasia. Ectopic ACTH: CT chest/abdomen/pelvis + Ga-68 DOTATATE PET-CT for occult source.

If the default doesn't apply

ACTH-independent (adrenal Cushing)

CT Adrenal CT with washout protocol or chemical-shift MRI (see adrenal-mass) IV contrast

Pituitary MRI negative — ACTH-dependent Cushing

Inferior petrosal sinus sampling (IR procedure) IV contrast

Ectopic ACTH suspected

NM CT chest/abd/pelvis + Ga-68 DOTATATE PET-CT (occult NET) IV contrast

Bilateral adrenal hyperplasia (PPNAD, AIMAH)

MRI Adrenal MRI for characterization IV contrast

Watch-outs

Incidental pituitary microadenoma

Up to 10% of adults have an incidental pituitary lesion — biochemistry must precede imaging or you'll over-call.

Adrenal incidentaloma in non-Cushing

Most adrenal incidentalomas are non-functional adenomas — don't reverse-engineer Cushing from imaging without biochemistry.

Pearls

Pituitary microadenoma: dynamic post-contrast sequences improve detection of sub-centimeter lesions.
Adrenal adenoma washout: absolute > 60% or relative > 40% at 15 min post-contrast.
DOTATATE PET-CT is the highest-yield study for occult ectopic ACTH source.
Bilateral adrenal nodular hyperplasia is rare — think McCune-Albright, Carney complex, PPNAD.