4,36) Most patients have no predisposing risk factors, but the presence of the following risk factors may lead to development of the tumor at a younger age: (37-38) primary sclerosing cholangitis (5-15% lifetime risk); choledochal cysts (5% will transform and risk increases with age); Caroli disease (7% lifetime risk); hepatolithiasis; chronic intraductal stones; bile duct adenoma; biliary papillomatosis; Clonorchis
sinensis infection; and Thorotrast (thorium dioxide) exposure.
Clonorchiasis, another parasitic disease of humans, is caused by ingestion of raw freshwater fish harboring infective Clonorchis
sinensis metacercariae (3,4).
Novel anti-parasitic compounds including 5-, 6-, and 7-member N heterocyclic rings (96, 97, and 98, respectively) were synthesised and used to kill parasites including blood flukes, cestodes, cysticercus, Clonorchis
sinensis, lung flukes, and Fasciolopsis buski in humans or animals (Yang et al.
Common human liver flukes include Clonorchis
sinensis, Opisthorchis viverrini, Fasciola hepatica and Schistosoma species.
Biliary parasites such as Clonorchis
sinensis and Opisthorchis viverrini, prevalent in parts of Asia, are also associated with carcinomas of the extrahepatic bile ducts.
Other flukes in the Trematoda class include Schistosoms, Fasciolopsis, and Clonorchis
Recent studies indicate that in China alone over the period 1995-2004 the incidence of one of the various parasitic infections in this group, clonorchiasis, tripled -- some 15 million Chinese were estimated to be infected with Clonorchis
sinensis in 2004.
Other microbial organisms associated with certain types of cancer include the liver fluke Clonorchis
sinensis, with bile duct cancer; schistosomiasis, with bladder cancer; and the common bacterium Helicobacter pylori, with gastric carcinoma and lymphoma.
Although presence of the liver fluke Clonorchis
sinensis is well documented in Vietnam (3), evidence of the presence of the more common liver fluke of Southeast Asia, Opisthorchis viverrini, is only circumstantial.
The following FZT species were identified: Clonorchis
sinensis (Opisthorchiidae), Centrocestus formosanus, Haplorchis pumilio (Heterophyidae), and Haplorchis yokogawi (Heterophyidae).
Although the origin of biliary papillomatosis has yet to be determined, chronic irritation by a stone, Clonorchis
infestation, reactive hyperplasia in Caroli disease, ectopic pancreatic tissue, and an anomalous arrangement of the biliary tree leading to chronic biliary injury by regurgitated pancreatic juice are among the factors that are considered to be possible causes.
Although these digenetic trematodes of the Opisthorchiidae family are closely related to the genera Clonorchis
and Opisthorchis, there are morphologic differences.