Treatment or Recurrence

MRI can adequately assess the regression in size of hydatids and the changes in host tissue during chemotherapy (Fig.3.53), and can show the residual debris after surgery or chemotherapy has destroyed a cyst. It is often possible, using serial scans, to recognize when any secondary infection is occurring or if treatment has been incomplete. (This is particularly important for alveolar hydatids caused by E. multilocularis, when incomplete removal is likely and will prove fatal without chemotherapy.)

....

Radioisotope Scanning

Radioisotope scanning can be useful in identifying the location, number, and size of liver hydatids, if ultrasound, CT or MRI are not available. In one series of 65 patients utilizing scans in 3 planes, the findings were as follows: (1) space-occupying "cold" lesions which were solitary in 44 patients, double in 16, and multiple in 5; 45 of the cysts were located in the right lobe; (2) morphological changes in hepatic size and shape with displacement or partial loss of the liver, and (3) occasional false-negative scans when the triplane technique was not used. As is the case also with abscesses, the filling defects caused by liver hydatids are usually more sharply defined than those due to infiltrating primary or metastatic neoplasms, but the isotopic appearance is nonspecific.

Radioisotope scanning may also be used (if CT and MRI are not available) to show defects in the brain: these will be single or multiple, usually round and often causing ventricular displacement or even hydrocephalus. Apart from localizing a "space occupying" mass, the scans are not specific.

Selective Celiac or Hepatic Angiography

Selective celiac or hepatic angiography (although rarely utilized today) can be useful in localizing hydatid cysts, in identifying unsuspected small cysts, and in planning the proper surgical approach. In the arterial phase, there will be displacement and stretching of the branches of the hepatic artery around one or more avascular cysts (Figs. 3.54 and 3.55). In the capillary and venous phases, a circular, well defined filling defect is seen on the hepatogram, and in most cases a rim of increased opacification measuring 0.5 to 4 mm surrounds the cyst. This represents compressed host vessels and is useful in differentiating hydatid cysts from nonparasitic cysts, primary neoplasms, and metastases. However, a liver abscess may show a wider, or similar, rim of increased vascularity due to inflammatory changes in its wall.

....

Fig. 3.55 Noncalcified liver hydatid identified on T-tube cholangiography and hepatic arteriography. (A) There is contrast filling of an irregular cyst cavity in the right lobe of the liver on a T-tube cholangiogram. This hydatid cyst had previously ruptured into one or more branches of the right hepatic duct, which often leads to suppuration and gas formation within the cyst. (B) Late arterial and (C) capillary phases of a selective hepatic arteriogram showing at least two irregular, avascular filling defects in the right lobe of the liver, with stretching of hepatic artery branches around them. The irregular nature of these noncalcified hydatid cysts is best seen in the hepatogram phase (C). There is some increased uptake in the walls of these cysts, probably due in part to secondary inflammation as a result of cyst rupture and communication with the biliary tree.