In a patient with non‑alcoholic steatohepatitis who has renal cysts and a 2 cm adrenal mass, what additional imaging should be performed?

Additional Imaging for 2 cm Adrenal Mass in NASH Patient with Renal Cysts

For this 2 cm adrenal incidentaloma, obtain a non-contrast CT of the abdomen to measure Hounsfield units (HU) as the essential first step—if HU ≤10, the lesion is definitively benign and requires no further imaging; if HU >10, proceed to either delayed contrast-enhanced CT (washout study) or chemical shift MRI for further characterization. 1, 2, 3

Initial Imaging Strategy

The non-contrast CT is the cornerstone of adrenal mass evaluation because it provides objective HU measurements that can definitively characterize many lesions without additional testing. 2, 3, 4

If HU ≤10 on Non-Contrast CT:

• The lesion is a benign lipid-rich adenoma—no further imaging is needed 1, 2, 3, 4
• This applies to masses <4 cm in size 2
• The patient can proceed directly to hormonal evaluation without additional imaging 3

If HU >10 on Non-Contrast CT (Indeterminate):

You have two equally appropriate second-line imaging options:

Option 1: Delayed Contrast-Enhanced CT (Washout Study)

• Obtain dynamic contrast-enhanced images followed by delayed images at approximately 10-15 minutes 1, 5
• Calculate relative percentage washout: [1 - (delayed HU / dynamic HU)] × 100% 5
• Benign adenomas demonstrate >50% relative washout; malignant lesions show <50% washout 5
• This approach has 98% accuracy for characterizing adrenal masses 5

Option 2: Chemical Shift MRI

• Particularly useful if the lesion was discovered on contrast-enhanced CT and you need characterization 1, 2
• Signal loss on out-of-phase imaging compared to in-phase imaging indicates benign adenoma 1, 4
• MRI may have better sensitivity and specificity than non-enhanced CT alone, correctly characterizing 89% of lesions with HU between 10-30 1
• Preferred if radiation exposure is a concern 2

Critical Hormonal Evaluation (Parallel to Imaging)

All adrenal incidentalomas require hormonal screening regardless of imaging appearance, as approximately 5% have subclinical hormone production. 3, 6

Mandatory Screening Tests:

• Plasma or 24-hour urinary metanephrines to exclude pheochromocytoma—this is non-negotiable before any contrast-enhanced imaging or biopsy 3, 6
• 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion 6
• Aldosterone-to-renin ratio only if hypertension or hypokalemia is present 3, 6

Size-Based Risk Stratification

For this 2 cm lesion specifically:

• Most masses <3 cm are benign (extensive workup not justified in patients without cancer history) 1, 3
• However, characterization is still warranted given the indeterminate nature at discovery 1
• Masses >5 cm should be surgically removed due to higher malignancy risk 1, 3

What NOT to Do: Critical Pitfalls

Never Perform Adrenal Biopsy Routinely:

• Biopsy is rarely indicated and carries unnecessary risks including tumor seeding and potential hypertensive crisis if unsuspected pheochromocytoma is present 1, 3
• Biopsy should only be considered if non-invasive imaging remains indeterminate AND there is a history of extra-adrenal malignancy 1
• Always exclude pheochromocytoma biochemically before any biopsy 1

Avoid Premature Advanced Imaging:

• Do not order FDG-PET for initial characterization—it is reserved for lesions that remain indeterminate after CT and MRI 1
• Plain radiography and ultrasound have very limited roles and should not be used 1

Do Not Skip Hormonal Evaluation:

• Skipping hormonal screening can lead to undiagnosed pheochromocytoma, which can cause life-threatening hypertensive crisis during any procedure 6
• Even radiologically benign-appearing lesions require one-time hormonal evaluation 6

Special Consideration: Renal Cysts

The presence of renal cysts in this patient does not change the adrenal imaging approach. 7 However, be aware that:

• Adrenal cysts (if this lesion proves to be cystic) are rare (1-2% of incidentalomas) and usually benign 7
• Cystic adrenal lesions should show low attenuation (<20 HU) on CT and characteristic fluid signal on MRI 7
• The 2 cm size makes a simple cyst less likely; solid masses require the standard characterization protocol outlined above 7