Abstract
Human cystic echinococcosis (hydatidosis) is a parasitic zoonosis with almost complete worldwide distribution. Echinococcus granulosus, the dog tapeworm, causes hydatidosis which accounts for 95% of human echinococcosis. Although this tapeworm is found in dogs as a definitive host and a number of intermediate hosts, humans are often infected from close contact with infected dogs. Humans are not part of the parasitic lifecycle and serve as accidental hosts. Hydatidosis is an important consideration in the differential diagnosis of hepatic cysts in individuals from endemic areas. Clinicians should be aware of the long incubation period, the high frequency of negative serological tests, and the possibility of intraoperative evaluations of the cyst aspirate being non-diagnostic. We describe a case of serology negative hydatidosis that came to medical attention as an incidental finding in a young woman from Bangladesh. The patient underwent imaging and was then started on albendazole. After several weeks of albendazole, the cyst was punctured, aspirated, injected with hypertonic saline, re-aspirated, and then fully excised. Diagnosis was confirmed by microscopic evaluation of the cyst aspirate. Serological tests for hydatidosis may be negative in patients with early disease and thus should not be used to rule out this disease. Consideration of this diagnosis allows clinicians to avoid the catastrophic spillage of cystic contents risking an anaphylactic reaction, which might prove fatal. Despite World Health Organization hydatidosis staging being based on ultrasound, radiologists in resource-rich setting may prefer MRI in the management and staging of cystic echinococcosis.