The degree of liver damage depends upon the number of flukes present, the duration of the infection and the number of reinfections that have occurred. The flukes may survive for many years (perhaps up to 20 years). Large numbers of parasites have been found in the bile ducts at autopsy in highly endemic areas. Fluke counts as high as 500-1,000 are common in the bile ducts in severe infections, with 6,000 and even 21,000 flukes counted in individual patients. Concomitant infection of the pancreatic duct may occur, resulting in dilatation and fibrosis of the duct. Flukes are sometimes found in the stomach, duodenum, and especially in the gallbladder (28 of 300 autopsies in one series), but they do not usually survive for long in these sites.

Complications of clonorchiasis include the formation of calculi, acute suppurative cholangitis, recurrent pyogenic cholangitis, acute pancreatitis, and cholangiocellular carcinoma of the liver.

Calculi are commonly found in the intrahepatic and common bile ducts as well as within the gallbladders of patients with clonorchiasis (70% of Hou's cases from Hong Kong). Reports from China and Japan suggest a possible etiological relationship between parasitism of the biliary tract and gallstone formation. Eggs and remnants of Clonorchis and Ascaris were found in the center of intrahepatic and common duct stones in 24 of 42 patients with chronic pyogenic cholangitis in Teoh's series from the Orient. Remnants of dead worms in the bile ducts may act not only as a nidus for gallstones but may also create the local changes of obstruction and infection that initiate calculus formation. When infection is heavy, localized dilatation of the bile ducts occurs as the maturing parasites increase in size and crowd together to plug the ducts. When stones are also present, together with biliary sand and debris, the resultant biliary stasis and obstruction favor bacterial infection which may lead to cholangitis, hepatic abscess, and liver failure.

Rarely, an acute suppurative cholangitis may develop in association with clonorchiasis and secondary Escherichia coli infection of the ducts. Much more commonly, particularly in China and Hong Kong, patients may develop a recurrent pyogenic cholangitis in association with clonorchiasis (especially in those patients with intrahepatic calculi). The infection is usually caused by E. coli, and probably reaches the liver through the portal venous system. (See discussion below in separate section on Oriental Cholangiohepatitis).

Acute pancreatitis of low mortality occurs in association with Clonorchis in the pancreatic duct, but prompt removal of the fluke results in full recovery. In Hong Kong, invasion of the pancreatic ducts by C. sinensis has been reported in up to 37% of patients with clonorchiasis examined at autopsy, but most have had no symptoms.

Carcinoma of the liver: Several large series suggest that clonorchiasis plays an important causal role in the unusually high incidence of cholangiocarcinoma in the Orient. The incidence of clonorchiasis in the general population in Hong Kong is 23%, but in those with cholangiocarcinoma it is 65%. The more common hepatocellular carcinoma of the liver occurs with great frequency in the Far East also, but does not appear to be associated with clonorchiasis.