Congenital dilatation of the large and segmental intrahepatic bile ducts (Caroli's disease) in two Golden retriever littermates.

Two, sibling, male Golden retriever puppies, 13 weeks of age, were presented with congenital biliary cysts of the liver involving both hepatic and segmental bile ducts, as well as bilateral polycystic kidney disease. Ultrasonography of the livers of both pups demonstrated segmental cystic lesions that were contiguous with the bile ducts. Histopathology revealed cystic ectatic bile duct hyperplasia and dysplasia with variable portal fibrosis in the liver, while in the kidneys there were radially arranged, cylindrically dilated cysts of the collecting ducts, which extended through the medulla and cortex. This pathology was compatible with that of congenital dilatation of the large and segmental bile ducts (Caroli's disease) described in humans, dogs and rats. In humans Caroli's disease has an autosomal recessive inheritance pattern, while in rats activation of the MEK5/ERK cascade initiates the biliary dysgenesis of Caroli's disease in this species. However, the exact mode of inheritance and pathogenesis of Caroli's disease in dogs is as yet unknown. Previous reports on congenital hepatic cystic diseases of the dog have described Caroli's disease like lesions in various breeds, but these are believed to be the 1st reported cases in the Golden retriever breed.