Meta Description: Learn how adrenal cysts appear on CT scan, how radiologists diagnose them, differential diagnosis, treatment options, and rare imaging clues in this complete guide.

Adrenal Cyst: Rare CT Imaging Diagnosis Every Clinician Should Know

A 36-year-old man arrives with abdominal pain. The symptoms are vague. Laboratory tests are often normal. But on CT scan diagnosis, a large cystic mass is found in the left adrenal region. What is it?

This is the classic scenario where medical imaging, especially CT scan radiology interpretation, changes the entire clinical pathway.

An adrenal cyst is an uncommon lesion arising from or adjacent to the adrenal gland. Most are benign and incidentally discovered, but some mimic malignancy, hemorrhage, infection, or retroperitoneal tumors. Because adrenal lesions can occasionally represent hormone-producing tumors or cancer, accurate radiology interpretation is critical.

In this article, we analyze a real imaging case of a large adrenal cyst and explain:

What are adrenal cysts
Why they occur
CT and MRI imaging features
Differential diagnosis
Diagnostic workflow
Treatment options
Prognosis

Clinical Case Summary

Parameter	Details
Age	36 years
Sex	Male
Presenting symptom	Abdominal pain
Imaging modality	Contrast-enhanced CT
Final diagnosis	Left adrenal cyst

Figure Review

Figure 1. Multiphasic Axial CT of Left Adrenal Cyst

(A) Non-contrast
(B) Arterial phase
(C) Portal venous phase
(D) Delayed phase

A well-defined cystic lesion is seen in the left adrenal region measuring approximately 7.1 × 7.2 × 7.2 cm. The lesion demonstrates low attenuation (~15 HU) without pathological enhancement across all phases. No mural nodule, septation, or calcification is identified.

Radiology Interpretation:
Lack of enhancement strongly supports a benign fluid-containing lesion rather than a solid adrenal neoplasm.

Figure 2. Coronal and Sagittal CT Reconstructions

(A) Coronal portal venous phase
(B) Sagittal portal venous phase

Reformatted images show the lesion arising from the left adrenal gland with a claw sign, confirming adrenal origin. Mild inferior displacement of the left kidney is present.

Radiology Interpretation:
The claw sign is highly valuable in determining the organ of origin for retroperitoneal masses.

What Is an Adrenal Cyst?

An adrenal cyst is a fluid-filled lesion associated with the adrenal gland. It may arise from vascular structures, embryologic remnants, prior hemorrhage, or parasitic infection.

These lesions are rare compared with common adrenal adenomas. Many are found accidentally during a CT scan diagnosis performed for abdominal pain, trauma, kidney stones, or cancer staging.

Pathophysiology

Adrenal cysts are classified into four main groups:

1. Endothelial Cysts

Most common true cysts. Derived from lymphatic or vascular channels.

Subtypes:

Lymphangiomatous cysts
Hemangiomatous cysts

2. Pseudocysts

Usually caused by prior adrenal hemorrhage. No epithelial lining.

3. Epithelial Cysts

Rare congenital lesions lined by epithelial cells.

4. Parasitic Cysts

Usually, hydatid disease is caused by Echinococcus.

Epidemiology

Rare lesion overall
Often diagnosed between the ages 30 and 60
Slight female predominance in some studies
Most lesions are unilateral
Increasing incidence due to widespread medical imaging

Clinical Presentation

Most adrenal cysts are asymptomatic. Symptoms usually occur when lesions become large.

Common Presentations

Abdominal pain
Flank discomfort
Early satiety
Nausea
Palpable mass (rare)
Incidental finding on CT or MRI

Rare Presentations

Hemorrhage
Infection
Hypertension (if associated with a functional adrenal lesion)
Compression of the kidney or pancreas

In this case, the patient had abdominal pain likely related to mass effect.

CT Imaging Features of Adrenal Cyst

Typical Benign CT Findings

Well-circumscribed lesion
Water or near-water attenuation
Thin wall
No internal enhancement
No solid component
No invasive features

In This Case

Size: 7.2 cm
Attenuation: 15 HU
No enhancement
No septa
No calcification
Downward displacement of the kidney
Left adrenal claw sign

These findings strongly support a benign adrenal cyst.

Why 15 HU Matters

Simple fluid often measures 0–10 HU. Proteinaceous fluid or old hemorrhage may measure slightly higher.

Thus, 15 HU is still compatible with a benign cyst, especially when no enhancement is seen.

MRI Features

MRI is useful when CT findings are indeterminate.

Typical MRI Appearance

T1: Low signal (unless hemorrhagic/proteinaceous)
T2: Very high signal
No post-contrast enhancement
Thin capsule

MRI can help distinguish a cyst from a hemorrhagic tumor or pheochromocytoma.

Can X-ray Detect an Adrenal Cyst?

Plain X-ray has limited value. Large lesions may produce:

Mass effect
Soft tissue opacity
Peripheral calcification (rare)

Modern diagnosis relies on CT scans and MRIs.

Differential Diagnosis

Large cystic adrenal-region masses require careful radiology interpretation.

Diagnosis	Key Imaging Clue
Adrenal cyst	Thin wall, no enhancement
Adrenal pseudocyst	Prior hemorrhage, complex fluid
Pheochromocytoma with necrosis	Enhancing solid tissue
Adrenal carcinoma	Irregular wall, invasion
Pancreatic pseudocyst	Pancreatic origin
Renal cyst	Renal cortical continuity
Splenic cyst	Splenic origin
Retroperitoneal lymphangioma	Multiloculated cystic mass

The Claw Sign Explained

When adjacent organ tissue wraps partially around a mass, it suggests that the mass originates from that organ.

In this case, the left adrenal gland forms a claw around the lesion, confirming adrenal origin.

This is a classic rare imaging teaching sign.

Diagnostic Workflow

Step 1: Confirm Cystic Nature

Use CT attenuation and enhancement patterns.

Step 2: Confirm Organ of Origin

Use multiplanar CT and the claw sign.

Step 3: Exclude Functional Tumor

Biochemical tests may include:

Plasma metanephrines
Cortisol testing
Aldosterone/renin (selected cases)

Step 4: Assess Malignancy Risk

Look for:

Nodules
Thick wall
Growth
Enhancement
Invasion

Step 5: Decide Observation vs Surgery

Based on size, symptoms, growth, and uncertainty.

Treatment

Observation

Appropriate when:

Asymptomatic
Benign imaging appearance
Stable size

Surgical Removal

Consider if:

Symptomatic pain
Large lesion (>5–6 cm in many practices)
Growth over time
Indeterminate imaging
Concern for malignancy
Hormonal activity

Surgical Options

Laparoscopic adrenalectomy
Cyst excision with adrenal preservation (selected cases)

Prognosis

Excellent for benign adrenal cysts.

Most patients recover fully after surgery if symptomatic. Recurrence is uncommon when adequately treated.

Clinical Storytelling Scenario

A young man presents with persistent left upper abdominal discomfort. Kidney stones are suspected. CT instead reveals a 7 cm retroperitoneal cyst near the kidney. At first glance, it could be renal, pancreatic, or splenic. But multiplanar reformats show the adrenal gland hugging the lesion—the claw sign. A potentially confusing mass becomes a confident diagnosis: benign adrenal cyst.

That is the power of expert radiology interpretation.

Key Takeaways

Adrenal cysts are rare but increasingly detected on CT.
Most are benign and incidental.
Lack of enhancement is a major reassuring feature.
Multiplanar imaging helps determine adrenal origin.
Large symptomatic cysts may require surgery.
Always exclude functional adrenal tumors.

Frequently Asked Questions

Is an adrenal cyst cancer?

Usually no. Most are benign. However, complex cystic adrenal masses require further evaluation.

Can an adrenal cyst cause pain?

Yes. Large cysts can compress nearby structures and cause abdominal or flank pain.

What size adrenal cyst needs surgery?

There is no absolute rule, but symptomatic or enlarging lesions and many lesions >5–6 cm are often considered for surgery.

Can CT diagnose an adrenal cyst accurately?

Yes. CT is one of the best tools for adrenal cyst diagnosis.

Quiz

Question 1. Which CT finding most strongly suggests a benign adrenal cyst?

A. Irregular enhancing wall
B. Invasion into the kidney
C. No enhancement with fluid attenuation
D. Enlarged lymph nodes
E. Internal solid nodule

Correct Answer: C. Explanation: Benign cysts usually show fluid attenuation and no enhancement.

Question 2. The claw sign helps determine:

A. Hormonal activity
B. Organ of origin
C. Presence of infection
D. Malignant grade
E. Renal function

Correct Answer: B. Explanation: The claw sign indicates the lesion arises from the adjacent organ.

Question 3. Which lesion is most likely to mimic an adrenal cyst?

A. Cataract
B. Pancreatic pseudocyst
C. Appendicitis
D. Gallstone ileus
E. Pneumothorax

Correct Answer: B. Explanation: Pancreatic pseudocysts can extend near the adrenal gland.

Adrenal Cyst on CT Scan: Complete Radiology Guide to Diagnosis, Imaging Features, and Treatment (Rare Medical Imaging Case)