Ultrasound images Metastases

The liver is one of the most common sites to which malignant tumours metastasize. Secondary deposits are usually blood-borne, spreading to the liver via the portal venous system (for example in the case of gastrointestinal malignancies), or hepatic artery (for example lung or breast primaries), or spread via the lymphatic system. Some spread along the peritoneal surfaces, for example ovarian carcinoma. This demonstrates an initial invasion of the subserosal surfaces of the liver (Fig. A), as opposed to the more central distribution seen with a haematogenous spread (Fig. B). The former, peripheral pattern is more easily missed on ultrasound because small deposits are often obscured by near-field artefact or rib shadows. It is therefore advisable for the operator to be aware of the possible pattern of spread when searching for liver metastases.

fig A

Peripheral secondary deposits due to peritoneal spread from a primary
ovarian carcinoma.

Ultrasound images Blood-borne metastases from bowel carcinoma are demonstrated in the central area of the liver
around the porta.

possible primary carcinoma and to identify other sites of carcinomatous spread. Lymphadenopathy (particularly in the para-aortic, paracaval and portal
regions) may be demonstrated on ultrasound, as well as invasion of adjacent blood vessels and disease in other extrahepatic sites including spleen,
kidneys, omentum and peritoneum.
Doppler is unhelpful in diagnosing liver metastases, most of which appear poorly vascular or avascular.
With the larger deposits, small vessels may be identified most often at the periphery of the mass.
The use of microbubble contrast agents has been shown to improve both the characterization sound. and detection of metastatic deposits on ultrasound
The injection of a bolus of contrast agent when viewed using pulse-inversion demonstrates variable vascular phase enhancement with no contrast uptake in the late phase.