Echinococcus granulosus infection can have multiorgan involvement, and is common in Third-World countries. Uncontrolled studies show that albendazole can be effective in its treatment, but there are also reports of spontaneous resolutions. We therefore undertook a placebo-controlled double-blind parallel-group randomized study in Iran to evaluate the effect of albendazole on hydatid cysts. Twenty-nine patients with 240 cysts entered the study in 1994-95 and received either albendazole (400 mg twice a day, in 3 cycles of 6 weeks with 2 weeks between cycles) or placebo. At study completion, 172 and 31 cysts in the albendazole and placebo groups, respectively, were evaluable. In the treatment arm, 134 cysts showed improvement or cure compared to 4 in the placebo group (P < 0.001). Eighteen (82%) of 22 patients in the treatment arm showed either cure (8 patients) or improvement (10 patients); in the placebo group only 1 (14%) of 7 showed spontaneous improvement but no cure. Some patients with liver cysts after treatment showed increasing heterogeneity and density suggestive of inactive cysts. Patients with larger cysts and those with pulmonary involvement were better responders. Age and gender had no effect on outcome. The observed results are encouraging, showing albendazole has good effect on hydatid cysts and should be offered to patients before surgical treatment is considered.

Infection with Echinococcus granulosus is endemic in Middle Eastern countries. Some patients are noted to undergo spontaneous resolution, but many require surgical removal with its associated risks. Although, there are studies showing favourable responses to medical treatment, there is no controlled study on the effect of albendazole. In this study, 20 patients with 179 E. granulosus cysts affecting the lungs were entered into a triple blind parallel randomized clinical trial comparing the effects of albendazole versus placebo. Fifteen patients (150 cysts) completed 6 months of treatment; four patients (26 cysts) were in the placebo group and 11 patients (124 cysts) in the treatment group receiving 800 mg albendazole daily in three cycles of 6 weeks with 2 weeks between cycles. Ten of 11 patients (91%) in the treatment group showed either cure (five patients) or improvement (five patients); in the placebo group, only one of four (25%) showed spontaneous improvement but no cure. In the treatment group, 88 of 124 cysts (71%) showed improvement compared to four of 26 (15.4%) in the placebo group (p=0.000). Complication from therapy was insignificant; one case had recurrent disease, which responded to further therapy. It is suggested that patients suffering from uncomplicated hydatid disease should be given a trial of albendazole before surgery is considered.

All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.