atypisches Leberhämangiom

Leberhämangiom Radiopaedia • CC-by-nc-sa 3.0 • de

Hepatic haemangiomas or hepatic venous malformations are the most common benign vascular liver lesions. They are frequently diagnosed as an incidental finding on imaging, and most patients are asymptomatic. From a radiologic perspective, it is important to differentiate haemangiomas from hepatic malignancy.

Terminology

It is important to note that according to newer nomenclature, these lesions are known as venous malformations (ISSVA classification of vascular anomalies) . Having said that, it is probably helpful to include the word 'haemangioma' in reports, as this term is ubiquitous in the literature and more familiar to many clinicians. The remainder of this article uses the terms 'hepatic haemangioma' and 'hepatic venous malformation' interchangeably.

Epidemiology

Hepatic haemangiomas are much more common in females, with an F:M of up to 5:1 . They are rarely seen in young children, but infantile hepatic haemangioma is the most common, benign hepatic vascular tumour in infants.

Associations

extrahepatic haemangiomata
hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu disease)
Kasabach-Merritt syndrome: with giant haemangiomas
hepatic arterioportal shunts

Pathology

Hepatic haemangiomas are thought to be congenital in origin, non-neoplastic, and are almost always of the cavernous subtype. Blood supply is predominantly hepatic arterial, similar to other liver tumours. A peripheral location within the liver is most common .

Subtypes

typical hepatic haemangioma
atypical hepatic haemangioma
- giant hepatic haemangioma
- flash filling hepatic haemangioma: up to 16% of all hepatic haemangiomas
- calcified hepatic haemangioma
- hyalinised/sclerosed hepatic haemangioma
- other unusual imaging patterns
  - hepatic haemangioma with capsular retraction
  - hepatic haemangioma with surrounding regional nodular hyperplasia
  - hepatic haemangioma with fatty infiltration
  - pedunculated hepatic haemangioma
  - cystic hepatic haemangioma: rare
  - fluid-fluid level containing hepatic haemangioma: rare

The presence of a few hepatic haemangiomas in the liver is not uncommon, but rarely a large number of hepatic haemangiomas may occur (see hepatic haemangiomatosis).

Radiographic features

Ultrasound

typically well-defined hyperechoic lesions
a small proportion (10%) are hypoechoic, which may be due to a background of hepatic steatosis, where the liver parenchyma itself is of increased echogenicity
colour Doppler: may show peripheral feeding vessels
contrast-enhanced ultrasound
- arterial phase: peripheral nodular discontinuous enhancement
- portal venous and delayed phases: continued "filling in" of the lesion, until the entire haemangioma is hyperechoic relative to background liver
- central haemorrhagic portions of cavernous haemangiomas remain non-enhancing

See hyperechoic liver lesions for a further differential.

CT

Most haemangiomas are relatively well-defined. The dynamic enhancement pattern is related to the size of its vascular space . Features of typical lesions include:

non-contrast: often hypoattenuating relative to liver parenchyma
arterial phase: typically show discontinuous, nodular, peripheral enhancement (small lesions may show uniform enhancement)
portal venous phase: progressive peripheral enhancement with more centripetal fill-in
delayed phase: further irregular fill-in and therefore iso- or hyper-attenuating to liver parenchyma

Other described features include:

bright dot sign

MRI

Typical features include:

T1: hypointense relative to liver parenchyma
T2: hyperintense relative to liver parenchyma, but less than the intensity of CSF or of a hepatic cyst
T1 C + (Gd): often shows peripheral nodular discontinuous enhancement which progresses centripetally (inward) on delayed images
- haemangiomas tend to retain contrast on delayed (>5 minutes) contrast-enhanced images
- atypical haemangiomas may demonstrate slightly altered enhancement patterns
T1 C + (hepatobiliary contrast, Eovist):
- in general, delayed imaging with Eovist/Gd- BOPTA may not be helpful since haemangiomas can have a variable appearance that ranges from hypointensity to diffuse and central enhancement
- high-flow haemangiomas may show 'pseudo washout' . This is thought to be due to increased contrast uptake from the adjacent liver parenchyma and should not be confused with true washout.
DWI: hyperintense on diffusion-weighted imaging even with high b-values due to slow blood flow and can be hyperintense or mixed (hyper and hypointense regions) on ADC map

Nuclear medicine

SPECT

Tc-99m RBC labelled SPECT can be sensitive for larger lesionsand typically demonstrate decreased activity on initial dynamic images followed by increased activity on delayed, blood pool images.

Treatment and prognosis

They are benign lesions. Recommendations for patients with no known risk factors for hepatic malignancy can range from centre to centre from performing confirmatory examinations (MRI, triphasic CT or scintigraphy) to considering follow-up ultrasound in 6 months to confirm stability, to performing no further imaging evaluation . Some authors propose surgical resection for patients with progressive abdominal pain in combination with a size greater than 5 cm .

Differential diagnosis

The diagnosis of haemangioma can usually be made with high specificity if the imaging characteristics are typical. General imaging differential considerations for a haemangioma depend on the imaging modality and the patient's history, but may include:

focal hepatic steatosis
- geographic hyperechoic lesion without mass effect or distortion of vessels (ultrasonography), requires dynamic phase CT or MRI for differentiation
hepatic metastases
- hypervascular hepatic metastases show marked early enhancement with a continuous ring that on later images fills in centrally and progressive centripetal fill-in may occur on delayed phases
hepatocellular carcinoma
hepatic cyst
- small lesions (generally less than 1 cm) on CT may be equivocal and can be clarified with a targeted ultrasound examination
hepatic abscess
regenerative nodules/dysplastic nodules
cystic hepatic or biliary neoplasm
haemangioendothelioma