Cystic disease of the liver and biliary tract.

The widespread availability of ultrasound imaging has led to more frequent recognition of cystic disease affecting the liver and biliary tract. There is a wide range of possible causes. Cystic disease of infective origin is usually caused by an Echinococcal species, or as the sequel of a treated amoebic or pyogenic abscess. The clinical and radiological features are often then distinctive and will not be dwelt upon in this review, except in respect of their contribution to the differential diagnosis of non-infective disorders. The principal non-infective cysts can be conveniently divided between the simple cyst, the polycystic syndromes (usually with coexistent renal disease), Caroli's syndrome, and choledochal cysts. The overlap between constituent members of these groups, and the association of cystic disease with hepatic fibrosis (especially with congenital hepatic fibrosis) has attracted considerable attention, and it has been suggested that they may all be considered to belong to a hepatobiliary fibrocystic continuum. In addition there are a variety of cystic neoplasms and a miscellany of unusual forms.