Can a 6.4 × 4.3 mm adrenal adenoma cause chronic diarrhea, could it be malignant, and what work‑up is indicated?

Adrenal Mass Evaluation: Chronic Diarrhea, Malignancy Risk, and Workup

Direct Answer

A 6.4 × 4.3 mm adrenal mass is far too small to be classified as an adrenal incidentaloma (which requires ≥1 cm), is extremely unlikely to cause chronic diarrhea, carries essentially no malignancy risk at this size, and requires no specific investigation or follow-up. 1

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Size Classification and Clinical Significance

This Mass Does Not Meet Incidentaloma Criteria

• By definition, adrenal incidentalomas must be ≥1 cm (10 mm) in size to warrant any evaluation or follow-up. 1
• Your mass measures 6.4 × 4.3 mm, which is below the threshold for clinical significance. 1
• Masses this small are considered normal anatomic variants or subclinical findings that do not require hormonal or radiologic workup. 1

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Can This Mass Cause Chronic Diarrhea?

No—This Mass Cannot Explain Chronic Diarrhea

• Hormonally active adrenal tumors that cause diarrhea (such as VIPomas or rare pheochromocytomas with diarrhea) are virtually always >2-3 cm and typically much larger. 2, 3
• At 6.4 mm, this mass is far too small to produce clinically significant hormone excess of any type. 1, 3
• Pheochromocytomas causing symptoms average 4-5 cm, and aldosterone-secreting adenomas causing hypertension/hypokalemia are typically 1-3 cm. 2, 3
• Your chronic diarrhea requires a separate gastrointestinal workup—this adrenal finding is an incidental red herring. 1

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Malignancy Risk Assessment

Malignancy Risk is Essentially Zero at This Size

• **Adrenocortical carcinomas are almost never <4 cm**, with most measuring >6 cm at diagnosis. 4, 2
• The 2023 CUA/AUA guidelines note that masses >4 cm have increased malignancy risk, implying that smaller masses (especially <1 cm) carry negligible risk. 1
• Metastases to the adrenal gland are also typically >1 cm when detected on imaging. 1
• At 6.4 mm, this mass is statistically irrelevant for malignancy consideration. 1, 4

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What Investigations Should Be Done?

No Adrenal-Specific Workup is Indicated

Because this mass is <1 cm, no hormonal testing, no repeat imaging, and no adrenal-specific follow-up is recommended. 1

What the Guidelines Say:

• The 2023 CUA/AUA guidelines explicitly state that adrenal masses must be ≥1 cm to qualify as incidentalomas requiring evaluation. 1
• No hormonal screening (no dexamethasone suppression test, no metanephrines, no aldosterone-to-renin ratio) is indicated for masses <1 cm. 1, 3
• No repeat imaging is recommended for masses this small. 1, 5

Focus on the Actual Clinical Problem:

• Investigate the chronic diarrhea with appropriate gastrointestinal evaluation: stool studies (infectious, inflammatory markers like fecal calprotectin), celiac serology, colonoscopy with biopsies, and consideration of functional diarrhea or bile acid malabsorption. 1
• Do not attribute the diarrhea to this tiny adrenal finding—it is a coincidental radiologic observation without clinical significance. 1, 3

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Common Pitfalls to Avoid

Do Not Over-Investigate This Finding

• Ordering hormonal panels for a 6.4 mm adrenal mass is inappropriate and will lead to false-positive results, unnecessary anxiety, and potential overtreatment. 1, 3
• Repeat imaging "just to be safe" is not evidence-based for masses <1 cm and wastes resources. 1, 5
• Attributing unrelated symptoms (like chronic diarrhea) to incidental sub-centimeter adrenal findings is a common diagnostic error that delays appropriate workup. 1, 6

When to Reconsider Adrenal Evaluation

• If future imaging (done for other reasons) shows the mass has grown to ≥1 cm, then initiate standard incidentaloma workup at that time. 1, 5
• If the patient develops clear signs of adrenal hormone excess (hypertension with hypokalemia, Cushingoid features, paroxysmal hypertension/palpitations), evaluate those symptoms independently—but this 6.4 mm mass is not the cause. 2, 3

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Summary Algorithm

1. Confirm the mass is <1 cm (6.4 mm qualifies). 1
2. No adrenal workup needed—no hormones, no repeat imaging. 1, 5
3. Pursue gastrointestinal evaluation for chronic diarrhea as a separate clinical issue. 1
4. Document in the chart that this sub-centimeter adrenal finding does not meet criteria for incidentaloma evaluation to prevent future unnecessary testing. 1, 7