Multifocal hepatic steatosis (also known as multifocal nodular hepatic steatosis) is the uncommon finding of multiple foci of focal fat in the liver mimicking - and at times being confused with - hepatic metastases.
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Epidemiology
Risk factors
Conditions that increase one's risk of developing multifocal hepatic steatosis are identical to other forms of steatosis:
- diabetes mellitus
- obesity
- chronic alcohol excess
- exogenous steroids
- drugs (amiodarone, methotrexate, chemotherapy)
- IV hyperalimentation
Clinical presentation
Multifocal hepatic steatosis is usually an incidental imaging finding.
Pathology
Radiographic features
The steatotic lesions vary from several millimeters to centimeters in size 1. They lack mass effect (i.e. they do not displace hepatic vessels or other structures) and display no internal vascularity .
Ultrasound
Focal steatosis on ultrasound usually forms a well-circumscribed area of echogenicity without mass effect. Acoustic shadowing may be present. Using color Doppler usually shows a complete absence, or only slight flow, within the affected liver 1,2.
CT
Focal steatosis on CT usually forms a low density lesion without mass effect or visible enhancement.
MRI
The most discriminating finding on MRI is the loss of intralesional signal on the out-of-phase sequence.
Signal characteristics
- T1: hyperintense signal
- T2: mildly increased signal
- T1 C+ (Gd-EOB-DTPA): on the hepatobiliary phase (20 minutes), uniform enhancement of the liver across both affected and unaffected regions
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IP/OP
- in-phase: hyperintense signal within the steatotic foci
- out-of-phase: loss of signal
- DWI/ADC: no abnormal restriction is usually seen