The diagnosis of HS is challenging, due to the lack of specific clinical signs, laboratory data and because radiological findings are often not pathognomonic.

Hepatic granulomas may be present in a wide spectrum of diseases (Fig. 5) and imaging plays a pivotal role for the differential diagnosis. However, confirmation of liver involvement is based on histopathology.

IMAGING EVALUATION OF HEPATIC SARCOIDOSIS

The grosser abnormalities in HS may be appreciated with ultrasound (US) imaging. However, both computed tomography (CT) and magnetic resonance (MR) are more sensitive for hepatic sarcoid-related lesions.

Ultrasound

US is usually the first imaging approach for the assessment of a patient with suspected HS.

The most common US findings are related to a diffuse involvement of the organ:

• Hepatomegaly

• Coarsening of the liver parenchyma

• Heterogeneous or homogeneous hyperechoic parenchyma

Hypoechoic or hyperechoic small nodules -reflecting focal involvement- can be rarely detected on US.

CT and MRI

CT and MRI allow for a better characterization of sarcoid-related focal lesions.

Small and scattered lesions represent coalescence of non-caseating granulomas:

• CT: hypodense nodules with low enhancement after iodinated contrast media administration (Fig. 6)

• MR: hypointense nodules on both T1- and T2-weighted images, with low intensity signal after para-magnetic contrast media administration (Fig. 7)

Other common findings are:

• Irregular liver margins (Fig. 8-9)

• Enlarged lymph nodes, in particular of the porta hepatis, paraaortic region and celiac axis (Fig. 10)

HS can rarely occur with atypical radiological findings, such as large lesions (i.e. greater than 30 mm) (Fig. 11-12) and higher signal intensity on T2-weighted images as compared to the more frequent hypointense nodules, probably due to active inflammation.

The main radiological differential diagnoses of hepatic sarcoid-related lesions include:

• multifocal liver lymphoma --> large liver lesions are often associated with bulky lymph nodes

• fungal infections --> liver involvement consists of small multiple lesions

• metastases and inflammatory diseases --> usually hyperintense lesions on T2 weighted fat-saturated images

Detection of complications in liver involvement

A small portion of patients (about 1%) with long-standing disease develops life-threatening complications of HS.

• Cirrhosis

• Portal hypertension

• Chronic cholestasis

• Portal vein thrombosis

• Budd-Chiari Syndrome

Imaging plays an important role for their evaluation (Fig. 13).