Alveolar Hydatid Disease

Infection with Echinococcus multilocularis yields images similar to invasive tumor growth and cannot be distinguished from a malignancy by sonography alone (Table 2.15).

Table 2.15 Alveolar hydatid disease. Sonographic classification after Wechsler and Kern7

Stage Characteristics

ICircumscribed inhomogeneous changes in the liver; ill-defined margin; mostly hyperechoic with a hypoechoic rim; calcification; no invasion of the portal vein, bile ducts, and hepatic veins

IIAppearance of hypoechoic cystic areas with ill-defined margins; invasion of bile ducts, branches of the portal vein, and hepatic veins; increasing calcification

IIIMarked infiltration of the liver with complications due to invasion of bile ducts and vessels; extensive calcification at the inhomogeneities; increasingly cystic hypoechoic areas

IV Crossing the organ boundary of the liver and invasion of the porta hepatis, diaphragm, retroperitoneum, head of the pancreas, and the duodenum

portance of diagnostic ultrasound increases considerably by using contrast agents.

Undoubtedly, abdominal sonography is the imaging modality of choice in the detection and diagnosis of hepatic disorders. Not only is it the most widely available alternative of all the imaging modalities, but it can be performed at any time, with a high degree of sensitivity

by hepatobiliary scintiscan (HIDA scan), which specifically detects the proliferating bile ducts of this disorder.

Laparoscopy. Laparoscopy is a minimally invasive procedure that permits a better assessment of the hepatic surface than any other method, precise guided biopsy of circumscribed lesions, and, with the option of an ultrasound scanner, a high-reso- lution study of the liver. It is used primarily for unknown diffuse disorders of the parenchyma, and in the preoperative work-up of malignant disease when the transabdominal ultrasound finding is negative.

Needle biopsy with cytology/histology/ bacterial culture. Needle biopsy is always an invasive procedure and can only be justified after one of the imaging methods listed above has been used and if it might lead to changes in the treatment—in which case it becomes a necessity.

Angiography. Today, angiography does not play any primary role in the diagnostic work-up of the liver. It is of limited value in the preoperative assessment of hepatic lesions or in transcatheter arterial chemoembolization (TACE).

Hepatocellular carcinoma. Any focal mass in a cirrhotic liver should be suspected of HCC and calls for further work-up and confirmation by ultrasound-guided needle biopsy (but only if it results in clinical consequences for the patient).

Noninvasive color-flow Doppler scanning may be able to demonstrate vascular invasion of the tumor or its bizarre irregular hypervascularization. CEUS demonstrates the typical bizarre early arterial vascularization in HCC. In addition, poorly differentiated tumor cells have a rapid wash-out effect compared to the surrounding parenchyma in the parenchymal phase.

After the application of specific contrast agents HCC is delineated by its filling defect on gadolinium-enhanced MRI.

Metastasis ( 2.14). Numerous proven methods can detect hepatic metastases, including transabdominal ultrasound (CEUS is particu-

larly effective) and the equally effective modalities of CT and MRI. Laparoscopy is the method of choice in the detection of small superficial metastases since it outperforms all other measures. At this time, typing a metastasis in terms of its primary can only be achieved by cytology/ histology. However, confirmation by ultra- sound-guided needle biopsy after color-flow Doppler study is called for only if it would result in clinical consequences. The canal of the biopsy should always run through a stretch of healthy parenchyma long enough to prevent hemorrhage. Lesions with a sonographic halo sign should be biopsied at the hypoechoic rim.