Background: Chemotherapy of cystic echinococcosis became a treatment option 25 years ago, when new anthelminthic drugs were introduced. Benzimidazole carbamates were shown to kill the entire metacestode stage of the parasite, and praziquantel exhibited an effect on protoscoleces. Continuous or intermittent treatment with albendazole is recommended for a period of up to 6 months, and praziquantel may enhance the effect, in particular in the case of cyst spillage. Degenerative changes in the cysts occur in approximately 75% of the patients by the end of the treatment period. Benzimidazoles have to be applied in high daily doses, and adverse effects are observed, such as leucopenia, elevation of liver transaminases, and alopecia. Unfortunately, prospective randomized trials on the efficacy of chemotherapy versus surgery are not available. New treatment methods, such as percutaneous puncture, aspiration, injection of scolicidal agents and re-aspiration (PAIR) or modified PAIR-based techniques, have received much attention, and in experienced hands these approaches yield rates of cure and relapse equivalent to those following surgery. Adjunct treatment with benzimidazoles is the cornerstone of the interdisciplinary approach in cystic echinococcosis.
Conclusion: The recent ultrasound WHO consensus classification of hepatic cysts is a major achievement, since on the basis of this classification prospective clinical trials can be initiated. The results of such studies may provide the basis for a stage-specific appropriate medical, interventional or surgical therapy, or even guide the clinicians to opt for 'watch and wait' by close observation without specific treatment.