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PATHOLOGY OF THE LIVER AND PORTAL VENOUS SYSTEM 85
and hyperechoic, as the blood clots. As it resolves
the haematoma liquefies and may contain fibrin
strands. It will invariably demonstrate a band of
posterior enhancement and has irregular, illdefined
walls in the early stages. Later on it may
encapsulate, leaving a permanent cystic ‘space’ in
the liver, and the capsule may calcify.
Injury to the more peripheral regions may cause
a subcapsular haematoma which demonstrates the
same acoustic properties. The haematoma outlines
the surface of the liver and the capsule can be seen
surrounding it. This may be the cause of a palpable
‘enlarged’ liver (Fig. 4.8B).
Intervention is rarely necessary and monitoring
with ultrasound confirms eventual resolution.
More serious hepatic ruptures, however, causing
haemoperitoneum, usually require surgery.
Haemangioma
These common, benign lesions are highly vascular,
composed of a network of tiny blood vessels. They
may be solitary or multiple. Most haemangiomas are
small and found incidentally. They are rarely symptomatic
but do cause diagnostic problems as they
can be indistinguishable from liver metastases. Their
acoustic appearances vary; the majority are hyperechoic,
rounded well-defined lesions; however,
atypical hypoechoic lesions or those with mixed
echogenicity cause particular diagnostic dilemmas.
Larger ones can demonstrate a spectrum of reflectivity
depending on their composition and may
demonstrate pools of blood and central areas of
degeneration. They frequently exhibit slightly
increased through-transmission, with posterior
enhancement, particularly if large. This is probably
due to the increased blood content compared with
the surrounding liver parenchyma (Fig. 4.9).
Because the blood within the haemangioma is
very slow-flowing, it is usually not possible to
demonstrate flow with colour or power Doppler
and the lesions appear avascular on ultrasound.
Microbubble contrast agents demonstrate a
peripheral, globular enhancement with gradual
centripetal filling of the lesion, helping to characterize
them and differentiate haemangioma from
malignant lesions.
When found in children, haemangiomas tend to
be large and do produce symptoms. These masses
produce shunting of blood from the aorta via the
main hepatic artery and, in extreme cases, present
with resulting cardiac failure. They are often heterogeneous
in appearance and larger vessels within
them may be identified with Doppler. Although
many regress over a period of time, others may
have to be embolized with coils under radiological
guidance to control the symptoms.
In patients with no cause to suspect malignancy,
it may be suggested that the appearances of a small,
A
B
Figure 4.9 (A) Three small haemangiomas (arrows). (B)
A haemangioma is demonstrated in the anterior part of
the right lobe of the liver.
(Continued)