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Adrenal gland

The adrenal glands (suprarenal glands) are paired endocrine organs located on the superior poles of the kidneys within the retroperitoneum. Each gland is enclosed in the renal (Gerota’s) fascia but separated from the kidney by perirenal fat. The right adrenal gland is pyramidal in shape and lies posterior to the inferior vena cava, while the left is semilunar and lies anteromedial to the upper pole of the left kidney, adjacent to the aorta and spleen.

Histologically, the adrenal gland consists of two distinct regions:

  • Cortex (outer region): subdivided into the zona glomerulosa (mineralocorticoids, mainly aldosterone), zona fasciculata (glucocorticoids, mainly cortisol), and zona reticularis (androgens).

  • Medulla (inner region): composed of chromaffin cells, secreting catecholamines (epinephrine and norepinephrine).

The adrenal glands are vital for regulating metabolism, stress response, electrolyte balance, and blood pressure. Pathologies include adrenal adenomas, pheochromocytomas, cortical carcinomas, metastases, and adrenal hyperplasia.

Synonyms

  • Suprarenal glands

  • Endocrine adrenal glands

Function

  • Cortex: secretes mineralocorticoids (aldosterone), glucocorticoids (cortisol), and androgens

  • Medulla: secretes catecholamines (epinephrine, norepinephrine)

  • Regulates stress response, metabolism, immune response, and blood pressure

Nerve Supply

  • Cortex: autonomic innervation, mainly sympathetic vasomotor fibers

  • Medulla: richly innervated by preganglionic sympathetic fibers from the thoracic splanchnic nerves via the celiac plexus; acts as a modified sympathetic ganglion

Arterial Supply

  • Superior suprarenal arteries (from inferior phrenic artery)

  • Middle suprarenal artery (directly from abdominal aorta)

  • Inferior suprarenal artery (from renal artery)

Venous Drainage

  • Right adrenal vein → drains directly into inferior vena cava (short and wide)

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

MRI Appearance

T1-weighted images:

  • Normal adrenal glands show intermediate signal intensity

  • Fat-containing adenomas may show signal drop on opposed-phase imaging

T2-weighted images:

  • Normal glands: intermediate signal

  • Pheochromocytomas: characteristically hyperintense (light bulb sign)

  • Hemorrhage or metastases show variable T2 intensity.

STIR:

  • Fat suppression highlights lesions, edema, or hemorrhage within adrenal glands

T1 Fat-Saturated (Pre-contrast):

  • Glands appear as intermediate signal structures against suppressed fat

  • Useful for lesion detection in periadrenal fat

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal glands enhance moderately and uniformly

  • Adenomas enhance rapidly but wash out quickly

  • Malignant lesions and pheochromocytomas enhance avidly and heterogeneously

MRI Non-Contrast 3D Imaging:

  • Provides 3D reconstruction of adrenal size, shape, and relations

  • Valuable in surgical planning and tumor localization

CT Appearance

CT Pre-Contrast:

  • Normal adrenals appear as soft-tissue density, Y- or V-shaped above kidneys

  • Adenomas often show low attenuation (<10 HU) due to lipid content

  • Detects calcifications, hemorrhage, or adrenal enlargement

CT Post-Contrast:

  • Normal glands enhance uniformly

  • Washout analysis differentiates adenomas from malignant lesions:

    • Adenomas show rapid washout (>50–60% at 10–15 minutes)

    • Malignant lesions show delayed washout

  • Useful for staging of carcinoma, pheochromocytoma, and metastasis

MRI images

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

MRI images

Adrenal gland MRI sag image anatomy image -img-00000-00000

CT image

Adrenal gland ct coronal image