Diagnostic Ultrasound - Abdomen and Pelvis

Focal Nodular Hyperplasia
TERMINOLOGY
Abbreviations
• Focal nodular hyperplasia (FNH)
Definitions
• Benign tumor of liver caused by hyperplastic response to
localized vascular abnormality
IMAGING
General Features
• Best diagnostic clue
○ Homogeneously isoechoic mass often with central scar
• Location
○ More common in right lobe
○ Usually subcapsular & rarely pedunculated
• Size
○ Majority are smaller than 5 cm (85%)
○ Mean diameter at time of diagnosis: 3 cm
• Key concepts
○ 2nd most common benign tumor of liver after
hemangioma
○ Most frequent hepatic tumor in young women
○ Benign congenital hamartomatous malformation
○ Accounts for 8% of primary hepatic tumors in autopsy
series
○ Usually solitary lesion (80%); multiple in 20%
○ Multiple FNHs associated with multiorgan vascular
malformations and certain brain neoplasms
Ultrasonographic Findings
• Grayscale ultrasound
○ Mass: Mostly homogeneous and isoechoic to
liver,occasionally hypoechoic or hyperechoic
○ Mass effect: Displacement of normal hepatic vessels and
ducts
○ Central scar: Mostly hypoechoic, may be hyperechoic
○ Prominent draining veins seen as hypoechoic nodules
around lesion
• Color Doppler
○ Spoke-wheel pattern
– Large central feeding artery with multiple small
vessels radiating peripherally
○ Large draining veins at tumor margins
○ Highly vascular tumor, but hemorrhage is rare
○ High-velocity Doppler signals
– Due to increased blood flow or arteriovenous shunts
• Contrast-enhanced ultrasound
○ Arterial phase: Brisk enhancement with spoke-wheel
pattern
– Centrifugal enhancement: More common in small (≤
3cm) FNH
○ Portal and delayed phase: No significant enhancement
or washout
CT Findings
• NECT
○ Isodense or hypodense to normal liver
• CECT
○ Hepatic arterial phase
– Transient, intense, and homogeneous enhancement
○ Portal venous phase
– Hypodense or isodense to normal liver
– Large draining veins → hepatic veins
○ Delayed phase
– Mass: Isodense to liver
– Central scar: Hyperdense due to fibrous tissue
– Scar visible in 2/3 of large (> 3 cm) & 1/3 of small FNH
MR Findings
• T1WI
○ Mass: Isointense to slightly hypointense
○ Central scar: Hypointense
• T2WI
○ Mass: Slightly hyperintense to isointense
○ Central scar: Hyperintense
• T1WI C+
○ Arterial phase: Homogeneously hyperintense
○ Portal venous: Isointense
○ Delayed phase: Isointense mass with retention of
contrast in central scar
• Specific hepatobiliary MR contrast agents
○ Gadoxetate (Eovist or Primovist)
– Bright homogeneous enhancement on arterial phase
– Delayed scan: Significant enhancement of scar
– Prolonged enhancement on hepatobiliary phase (20
minutes) scan
□ Iso-/hyperintense mass with hypointense central
scar
□ Due to functioning hepatocytes and malformed
bile ductules
□ Most specific test to distinguish from all other
hepatic masses
Angiographic Findings
• Conventional angiography
○ Arterial phase
– Hypervascular mass with hypovascular central scar
– Enlargement of main feeding artery with centripetal
blood supply
– Spoke-wheel pattern as on color Doppler
○ Venous phase: Large draining veins → hepatic veins
○ Capillary phase
– Intense & nonhomogeneous stain
– No avascular zones
Nuclear Medicine Findings
• Technetium sulfur colloid
○ Normal or increased uptake
○ Only FNH has both Kupffer cells & bile ductules
○ Almost pathognomonic in 60% of cases
• Tc-HIDA scan (hepatic iminodiacetic acid)
○ Normal or increased uptake
○ Prolonged enhancement (80%)
• Tc-99m tagged red blood cell scan (not useful)
○ Early isotope uptake and late defect
Imaging Recommendations
• Best imaging tool
○ CECT or contrast-enhanced MR for diagnosis
– MR with gadoxetate hepatobiliary phase scans is most
specific
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Diagnoses: Liver
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