Cystic hydatid disease: pitfalls in diagnosis in the Middle East endemic area.

Ultrasound (US) and computerized tomography (CT) have made a significant contribution to accurately localizing focal lesions. Such imaging techniques have been found useful in assessing a hydatid aetiology of cystic lesions. However, we present 23 cases which demonstrate that these modalities in isolation are not adequate in diagnosing hydatid cysts, as claimed from this geographic area. Simple, congenital, choledochal and pancreatic pseudocysts were cystic lesions misinterpreted as hydatid cysts, as were infective disorders such as amoebiasis and tuberculosis. The appearance of a lipoma and an ovarian intra-abdominal cystadenoma and an intra-hepatic haematoma were among other conditions that were labelled as hydatid cysts on US/CT. However, in all the cyst/mass lesions that were misdiagnosed, counter-immunoelectrophoresis (CIEP), with an antigen that elicits an arc-5 in immunoelectrophoresis on cellulose acetate membranes as a substrate, did not detect any anti-Echinococcus antibodies in patients' sera. This was in contrast to the classic indirect haemagglutination test which was equivocal in some cases. The CIEP was specific and excluded hydatidosis though such a diagnosis was ventured on US and/or CT. We therefore conclude that a specific and sensitive serological test is mandatory for confirming a preoperative diagnosis of CHD. When surgery is not immediate, a negative serological test such as the CIEP would in addition indicate US or CT-guided aspiration of cyst fluid for cytological evaluation and/or enzyme immunoassay, thereby avoiding the cost and morbidity of laparotomy. Furthermore, chemotherapy is now a viable alternative provided the diagnosis is unequivocal. This may be a prudent protocol before a further decision on management is envisaged.