Evaluation of the Liver for Metastatic Disease

Erik K. Paulson, MD1, 1Department of Radiology, Duke University Medical Center, Durham, North Carolina.

Semin Liver Dis. 2001;21(2) 

In This Article

Ultrasound

Because of its low capital equipment cost and lack of ionizing radiation, transabdominal US is used frequently to screen the liver for metastatic disease.[1] In most patients, the majority of the liver is well visualized using either the subcostal or intercostal approach. The disadvantages of US are its dependency on operator skill and relative lack of reproducibility from one scan to the next. In many patients the dome of the liver is difficult to evaluate with ultrasound. In obese patients or those with fatty infiltration, it may be difficult or impossible to penetrate the liver with sound. Similarly, overlying ribs or gas-filled loops of bowel limit sound penetration. Despite the potential advantages of ultrasound, many surgeons and oncologists trained in the United States choose to rely on CT or MRI rather than US for screening and/or following patients with metastatic disease.[1] The sensitivity of ultrasound for detecting metastases is similar to that of noncontrast-enhanced CT.

Color Doppler US or power Doppler US has been used to characterize the blood flow within and around hepatic metastases, although the addition of these modalities to conventional gray-scale scanning offers little in terms of detection.[17,18,19,20,21,22,23] Interestingly, recent work suggests that hepatic arterial blood flow is increased in patients with metastatic disease.[24,25,26,27,28] Leen et al[25,26] report that the ratio of hepatic artery to portal flow (called the Doppler perfusion index, or DPI) is sensitive for determining the presence of metastatic disease. Even more promising is work that suggests this ratio may be used to identify patients with primary tumors who are at risk for developing metastatic disease on follow-up scans. These promising early results await the result of further scientific inquiry before they can be incorporated into routine clinical practice.

Several injectable US agents have been developed and hold promise for increasing the sensitivity of ultrasound for detecting metastatic disease.[29,30,31,32,33,34,35,36,37,38] The agents either enhance blood flow visualization within or around lesions or enhance the visualization of normal parenchyma. Although US contrast agents show promise in regard to the detection and characterization of metastatic disease, their role in the evaluation of patients with metastases awaits the results of scientific investigation. It is doubtful that contrast-enhanced US will replace well-performed CT and MRI for detecting patients with metastatic disease of the liver.

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