Diagnostic Ultrasound - Abdomen and Pelvis

Adrenal Adenoma
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Diagnoses: Adrenal Gland
Adrenal Hemorrhage
• Chronic hematoma may mimic adenoma: Well defined,
oval, and hypoechoic on US
• No enhancement on CECT or CEMR
Adrenal Myelolipoma
• Can be small or large; asymptomatic
• Often homogeneous but typically more hyperechoic
• CT shows macroscopic fat, which is diagnostic
• Lipid-rich adenoma shows greater signal loss on chemical
shift MR, whereas myelolipoma shows greater signal loss
on fat-saturated sequences
Pheochromocytoma
• Typically large, > 3 cm in most cases
• Small tumors may be homogeneous isoechoic/hypoechoic
• Characteristically very hyperintense on T2WI
• Prone to hemorrhage and necrosis
• Characteristic clinical syndrome and endocrine dysfunction
Adrenal Carcinoma
• Rare; most commonly large and heterogeneous
• When small, can appear homogeneously hypoechoic
PATHOLOGY
General Features
• Classified as nonfunctioning vs. functioning
○ Most are nonfunctioning (normal hormone levels)
○ 15% are functional and produce hormones
– Glucocorticoids result in Cushing syndrome
– Mineralocorticoids result in Conn syndrome
– Androgens result in virilization of women or
feminization of men
○ Cushing syndrome
– 15-25% are due to adrenal adenoma; usually > 2 cm
– More commonly due to adrenal hyperplasia
○ Conn syndrome (primary hyperaldosteronism)
– 80% are due to adrenal adenoma; often < 2 cm
– 20% are due to adrenal hyperplasia
Gross Pathologic & Surgical Features
• Encapsulated, well-circumscribed, tan-yellow, ovoid mass
• Necrosis and hemorrhage are rare
Microscopic Features
• 70% show high intracytoplasmic lipid content
• 30% are atypical with lipid-poor features
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Most commonly: Asymptomatic, incidental finding
– Accounts for > 90% of all incidentalomas
○ Hypertension and weakness with Conn syndrome
○ Moon facies, truncal obesity, purple striae, and buffalo
hump with Cushing syndrome
• Other signs/symptoms
○ Lab data: ↑ aldosterone, cortisol, &/or androgens
Demographics
• Age
○ Prevalence of adenoma increases with age
○ Peak at 60-69 years, decreasing thereafter
• Gender
○ M = F
• Epidemiology
○ Most common adrenal tumor
○ Detected with increasing frequency in recent years due
to increased use of CT and MR
○ Occurs in up to 9% of population (autopsy studies)
○ ↑ incidence in patients with diabetes or HTN
Natural History & Prognosis
• Excellent prognosis when incidental and
nonhyperfunctioning
Treatment
• No treatment when asymptomatic incidental finding
• Laparoscopic removal of gland if hyperfunctioning
○ Unilateral aldosterone secretion on adrenal vein
sampling may be treated surgically
DIAGNOSTIC CHECKLIST
Consider
• Small, asymptomatic adrenal nodule most likely to
represent adrenal adenoma
• Consider comparison with any available prior imaging to
establish stability over 12 month period and avoid
unnecessary additional testing
Image Interpretation Pearls
• No specific sonographic features distinguish adenomas
from other adrenal lesions
○ May suggest diagnosis for small, well-circumscribed,
homogeneous lesion on US
• CT and MR show specific patterns that can confirm
○ Lipid-rich adenomas
– NECT: < 10 HU
– Chemical shift MR: Signal drop on out-of-phase T1
○ Lipid-rich and lipid-poor adenomas
– 10 min delayed-phase CECT: > 60% washout on 10
min delay
SELECTED REFERENCES
1. Lattin GE Jr et al: From the radiologic pathology archives: Adrenal tumors
and tumor-like conditions in the adult: radiologic-pathologic correlation.
Radiographics. 34(3):805-29, 2014
2. Berland LL et al: Managing incidental findings on abdominal CT: white paper
of the ACR incidental findings committee. J Am Coll Radiol. 7(10):754-73,
2010
3. Johnson PT et al: Adrenal mass imaging with multidetector CT: pathologic
conditions, pearls, and pitfalls. Radiographics. 29(5):1333-51, 2009
4. Caoili EM, et al. Adrenal masses: characterization with combined
unenhanced and delayed enhanced CT. Radiology 2002; 222:629-33.