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Adrenal glands

The adrenal glands (also called suprarenal glands) are paired endocrine organs located in the retroperitoneum, sitting on the superior poles of the kidneys. They are yellowish, triangular (right) and semilunar (left) in shape. Each gland has two distinct regions:

  • The cortex, derived from mesoderm, which produces steroid hormones (mineralocorticoids, glucocorticoids, and androgens)

  • The medulla, derived from neural crest cells, which secretes catecholamines (epinephrine and norepinephrine)

The adrenal glands are surrounded by perirenal fat and enclosed within Gerota’s fascia.

Synonyms

  • Suprarenal glands

  • Endocrine adrenal organs

  • Epinephric glands

Function

  • Cortex:

    • Zona glomerulosa → mineralocorticoids (aldosterone) for sodium and water balance

    • Zona fasciculata → glucocorticoids (cortisol) for metabolism and stress response

    • Zona reticularis → androgens (DHEA) for secondary sex characteristics

  • Medulla:

    • Secretes catecholamines (epinephrine, norepinephrine) for fight-or-flight response

  • Regulates blood pressure, metabolism, and stress adaptation

Arterial Supply

  • Superior suprarenal arteries from the inferior phrenic artery

  • Middle suprarenal artery from the abdominal aorta

  • Inferior suprarenal artery from the renal artery

Venous Drainage

  • Right adrenal vein drains directly into the inferior vena cava

  • Left adrenal vein drains into the left renal vein (sometimes via the left inferior phrenic vein)

Nerve Supply

  • Sympathetic innervation via the celiac plexus and thoracic splanchnic nerves

  • Preganglionic sympathetic fibers synapse directly on chromaffin cells of the medulla

  • Parasympathetic supply is negligible

MRI Appearance

T1-weighted images:

  • Adrenal glands are intermediate to low signal relative to the liver

  • Surrounded by hyperintense perirenal fat, outlining their shape

  • Adenomas may appear hypointense compared to liver, lipid-rich lesions show signal drop on chemical-shift imaging

T2-weighted images:

  • Normal glands are intermediate signal

  • Adenomas = variable (often hypointense)

  • Pheochromocytomas = markedly hyperintense ("light bulb sign")

  • Cysts/hemorrhage = hyperintense

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, improving detection of edema, hemorrhage, or tumor infiltration

  • Pathological lesions appear hyperintense, aiding distinction from surrounding fat

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal adrenal glands enhance moderately and homogeneously

  • Adenomas typically enhance and wash out rapidly (assessed with dynamic sequences)

  • Malignant tumors (carcinomas, metastases) show heterogeneous enhancement

  • Pheochromocytomas enhance intensely and heterogeneously

CT Appearance

Non-contrast CT:

  • Adrenal glands appear as soft tissue density structures with Y, V, or triangular shape

  • Adenomas: often <10 HU due to lipid content

  • Calcifications may be present in old infections or hemorrhage

Contrast-enhanced CT (CECT):

  • Normal glands enhance homogeneously

  • Adenomas enhance but demonstrate rapid washout

  • Carcinomas/metastases show delayed, heterogeneous enhancement

  • Best modality for size assessment, calcifications, hemorrhage, and washout calculations

MRI image

adrenal gland anatomy MRI coronal image -img-00000-00000

CT image

adrenal gland anatomy CT axial image -img-00000-00000