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By the time alveolar hydatids are detected in the liver, the parasitic growth has usually caused stenosis, local dilatation, or displacement of the bile ducts, and given rise to portal vein and inferior vena cava thrombosis and/or thrombosis of hepatic veins and arteries. It is therefore not surprising that mortality rates in untreated or inadequately treated patients are high: in one series of 66 patients, 70% died within five years, and 94% within 10 years after diagnosis. In a recent study of 21 patients, the average survival time was 5.3 years after diagnosis, and 100% died within 14 years (Ammann and Eckert, 1995).

When the lungs are involved with alveolar hydatids, conventional chest radiography shows multiple irregular, spherical and lobulated masses, 1.5 to 3 cm in diameter, mainly in the lower lobes and in a peripheral subpleural position (Fig. 3.164). Chest CT shows central hypodensity and, in some cases, amorphous peripheral calcification within these masses.

Metastatic alveolar hydatids in the brain may appear as late as 10 years after onset of the disease. In 11 patients, Bensaid et al (1994) found alveolar hydatids in these locations: four parietal, three temporal, and four in the frontal or posterofrontal areas. Two features were different from alveolar hydatids in the liver: (1) extirpation of masses in the brain is easier due to better defined margins and (2) protoscolices are found more often in brain than in liver lesions. These alveolar cysts of the brain appear on CT and MRI as grape-like, multilocular cystic masses with definite margins; calcification and surrounding edema is common (Figs. 3.170 and 3.171). Contrast enhancement occurs with inflammatory reaction around the cysts. If there is ring-enhancement, bacterial abscess, tuberculoma, or cysticercosis have to be excluded; otherwise, glioma, especially oligodendroglioma, must be included in the differential diagnosis.

Early diagnosis and treatment significantly improves the prognosis of alveolar echinococcosis. It is therefore important to discover this very serious disease in an early stage. In highly endemic areas or in a highly exposed population, serological or ultrasound screening of the abdomen may be justified. In selected cases, this may be combined with CT and/or MRI. For serological screening, a highly sensitive and specific Em2 plus ELISA kit is now commercially available.

Fig. 3.170 E. multilocularis involvement of the orbit and brain of a patient from Alsace, France. (A) Contrast-enhanced CT reveals a round right palpebral mass (1). (B) A large right frontal lobe mass is present with posterior displacement of the corpus callosum, posterior and contralateral displacement of the right frontal horn and contralateral displacement of the falx cerebri. Nodular and ring-like calcifications are seen within the mass, which shows partial contrast enhancement and is surrounded by edema (2). Nonenhancing and noncalcified areas represent alveolar hydatid cysts (3). (C) The inner table of the skull (4) is irregular anterior to the mass. (Courtesy of Dr. J.L. Dietemann, Strasbourg, France and Neuroradiology, 1994).

Fig. 3.171 (A) T1-weighted MR image on the same patient reveals a heterogeneous low signal within the right frontal lobe mass. (B and C) Heterogeneous contrast enhancement is present within the mass. The inner table of the cranial vault appears irregular (1) and there is dural enhancement (2). The calcified areas show low signal intensity. There is ring enhancement of the low intensity palpebral mass (3), which shows high signal (4) on a T2-weighted image (D). On proton density (E) and T2-weighted images a grape-like low signal right frontal mass was identified, surrounded by high signal edema. (Courtesy of Dr. J.L. Dietemann, Strasbourg , France and Neuroradiology, 1994).

Treatment of Alveolar Echinococcosis

(1) Surgical resection of the parasite in all organs.
(2) Long-term chemotherapy of inoperable patients.
(3) Long-term complementary chemotherapy in patients with incomplete surgical resection, and at least 2 years of chemotherapy in patients after radical surgery or liver transplantation for alveolar echinococcosis (Bresson et al, 1991).

Contraindications for chemotherapy (with mebendazole and albendazole, as of 1999) are few due to relatively low toxicity, but some patients show severe drug intolerance in the final clinical stages, and certain precautions and modifications of drug administration are necessary. About 60% of the patients under treatment showed clinical improvement (increased body weight, regression of cholestasis, decrease in liver lesion size), 20% showed stabilization, and 20% progression. The ten-year survival rate in a group of 70 treated patients was 89% as compared to 6% in untreated patients (Eckert et al, 1995). Recurrences are frequent after discontinuation of long-term treatment of inoperable patients; however, they seem to respond favorably again following renewal of therapy.

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