LIVER HAEMATOMA HAEMANGIOMA

Haematoma
The liver haematoma may have similar acoustic appearances to those of an abscess, but does not share the same clinical features. A haematoma is the result of trauma (usually, therefore, via the Accident and Emergency department) but the trauma may also be iatrogenic, for example following a biopsy procedure (hence the value of using ultrasound guidance to avoid major vessels in the liver) or surgery. The acoustic appearances depend upon the timing a fresh haematoma may appear liquid and echo-poor, but rapidly becomes more solid-looking 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. 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.

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, well-defined, hyperechoic mass are due to benign haemangioma. Follow-up scans will demonstrate no appreciable change over time. However, where doubt exists, it is useful to refer the patient for further imaging, such as MRI scanning, to characterize the lesion confidently. Administration of an ultrasound contrast agent is also useful in lesion characterization and a haemangioma usually demonstrates a peripheral, nodular enhancement pattern in the arterial phase, with gradual centripetal filling.