Adrenal Gland Ultrasound: Normal Anatomy, Incidentalomas, and Technique

The adrenal glands are small, often overlooked, and technically challenging to image. Most sonographers see them on abdominal scans only when they're abnormal. Here's what you need to know about adrenal anatomy, technique, and findings.

Anatomy

The adrenal glands (suprarenal glands) sit in the retroperitoneum, superior and slightly medial to each kidney. They are small — approximately 3–6 cm in length, 2–3 cm wide, and only 3–6 mm thick in their limbs.

Shape: Triangular or "Y"-shaped. The right adrenal is more pyramidal; the left is more crescentic and elongated.

Right adrenal: Located posterior to the IVC, lateral to the right crus of the diaphragm, and just above the right kidney.

Left adrenal: More medial and inferior than the right — lies between the aorta and upper pole of the left kidney, medial to the spleen.

Echogenicity: Normal adrenals are isoechoic or slightly hyperechoic relative to the surrounding retroperitoneal fat. The central medulla may be slightly more echogenic than the outer cortex.

Scanning Technique

The adrenals are notoriously difficult to visualize in adults — unlike in neonates (where they're proportionally large and easily seen). Adequate technique matters.

Right Adrenal

Approach: Coronal through the right lobe of the liver (liver as acoustic window).

1. Position the probe in the right lateral intercostal spaces — liver as window
2. Identify the right kidney and IVC
3. Look for the right adrenal between the upper pole of the right kidney, the IVC, and the right crus of the diaphragm
4. The right crus of the diaphragm appears as a hypoechoic muscular structure — the adrenal is anterior to it
5. In many patients, the right adrenal is visible as a small "V" or "Y" of similar echogenicity to surrounding fat

Tip: Patient in full inspiration holds the liver down, improving the window. Adjust decubitus position if needed.

Left Adrenal

Approach: Lateral or coronal approach through the spleen (splenorenal window) or the left kidney.

1. Patient in right lateral decubitus (left side up) often improves left-sided windows
2. Use the spleen as your acoustic window
3. Identify the left kidney and aorta
4. The left adrenal sits medial to the upper pole of the left kidney, between the kidney and the aorta/left crus
5. It's often partially obscured by bowel gas — have patience

Reality check: In many adult patients — especially those with moderate body habitus or bowel gas — the adrenals are not visualized. This is normal and should be documented: "Right/left adrenal gland not visualized — no focal mass identified in the expected anatomical region."

Normal Measurements

Measurement	Normal
Maximum limb width	< 10 mm (limb, not entire gland)
Length	3–6 cm

Key: The limb thickness is more clinically meaningful than overall size. A limb > 10 mm is considered suspicious for pathology.

Adrenal Pathology

Adrenal Adenoma (Most Common Adrenal Mass)

Most adrenal masses are benign adenomas — found incidentally during imaging performed for other reasons.

Sonographic appearance:

• Well-defined, rounded, homogeneous mass
• Usually hypoechoic (but can be isoechoic or slightly hyperechoic)
• Typically small (< 3–4 cm)
• No internal vascularity on Doppler (or very minimal)

The problem: Ultrasound cannot reliably characterize lipid content (which differentiates benign adenoma from malignancy). Any adrenal mass > 1–2 cm found on ultrasound should be further evaluated with CT or MRI.

Adrenal Incidentaloma

An adrenal mass discovered incidentally — not the reason for the scan.

What to document: Size (three dimensions), location, echogenicity, internal vascularity, presence of calcification.

Always recommend: CT adrenal protocol or MRI for any adrenal mass ≥ 1 cm found on ultrasound. Lipid-rich adenoma = fat content measurable on CT (< 10 HU). Lipid-poor or indeterminate masses need MRI chemical shift imaging.

Reporting language: "1.8 cm well-defined hypoechoic mass identified in the right adrenal region. CT of the adrenal glands is recommended for further characterization."

Adrenal Cyst

• Purely anechoic, thin-walled, posterior enhancement
• May be simple (benign) or complex (hemorrhagic, pseudocyst)
• Simple adrenal cysts are benign if criteria are met

Pheochromocytoma

A catecholamine-secreting tumor — causes hypertensive crises, headaches, sweating, and palpitations.

Ultrasound appearance:

• Often large (> 3–4 cm at presentation)
• Heterogeneous — may have cystic areas, hemorrhage, or calcification
• Hypervascular on color Doppler
• May be bilateral (in hereditary syndromes — MEN2, VHL, NF1)

Clinical note: Before any biopsy or procedure on a suspected pheochromocytoma, the patient must be biochemically screened — unblocked pheochromocytoma manipulation can cause hypertensive crisis.

Adrenal Metastasis

The adrenal glands are a common site of metastasis — lung, breast, colon, melanoma, and renal cell carcinoma all metastasize here.

Ultrasound appearance:

• Variable — can be small and homogeneous (mimicking adenoma) or large and heterogeneous
• Bilateral in many metastatic cases
• History of malignancy is the key clinical context

If a patient with known malignancy has new adrenal masses on ultrasound — flag it.

Adrenal Hemorrhage

In neonates, adrenal hemorrhage is a common cause of adrenal mass. In adults, it occurs with trauma, anticoagulation, or severe stress (sepsis).

Evolution on ultrasound:

• Acute: echogenic mass (hyperechoic blood)
• Subacute (days–weeks): complex, mixed echogenicity
• Chronic: hypoechoic or cystic, may calcify

Serial ultrasound to confirm resolution is appropriate for suspected adrenal hemorrhage.

Key Images to Capture

1. Right adrenal region — long axis with any measurable structure
2. Left adrenal region — long axis
3. Any adrenal mass — three dimensions in two planes
4. Color Doppler of any mass
5. Document "not visualized" if unable to identify in a technically adequate study

---

SonoBuddy's abdominal protocols include the adrenal gland as part of the retroperitoneal survey. Normal adrenal measurements are in the Measurements section.