What is liver ultrasonography?
Liver ultrasonography involves the detection of tumors with a probe emitting high-frequency sound waves, which are bounced back to the probe by tumors.
How is it performed?
Liver ultrasonography is performed with a hand-held probe, which is placed on the abdomen over the liver.
How sensitive is this test?
The sensitivity of liver ultrasonography varies with the experience of the examiner. It is reported to be only 20% effective for metastases less than 10 mm in diameter. The sensitivity is lower in obese patients and those with a high diaphram or if the intestine is in the way.
What about false positive results?
False-positive results can be caused by lesions such as hemangioma and cyst. Some healthy individuals have benign liver tumors.
Can the sensitivity of ultrasonography be enhanced?
The sensitivity can be enhanced using intravenous contrast media, such as Sonovue (sulphur hexafluoride with phospholipid gel). A bolus of 2.4 mL is injected intravenously. Such enhancement is especially helpful in detecting metastases smaller than 10 mm. Melanoma metastases tend to be hypervascular so that they are hyper-reflective compared to the surrounding liver in the arterial phase, becoming relatively hypo-reflective later in the scan. With contrast, ultrasonography is reported to be as sensitive as computerised tomography (CT) and magnetic resonance imaging (MRI). As with standard ultrasonography, ultrasound with contrast depends on the skill of the examiner and is less sensitive in obese patients.