Clonorchis sinensis: pathogenesis and clinical features of infection.

When larvae of C. sinensis reach the biliary system and mature, the flukes provoke pathological changes, both as a result of local trauma and of toxic irritation. The appearances vary with duration and severity of the infestation, but they are sufficiently distinctive and characteristic to allow a classification into four phases as follows; 1st phase, desquamation of epithelial cells, 2nd phase, hyperplasia and desquamation of epithelial cells, 3rd phase, hyperplasia and desquamation of epithelial cells, and adenomatous tissue formation, and 4th phase, marked proliferation of the periductal connective tissue with scattered abortive acini of epithelial cells and fibrosis of the wall of the bile duct. The onset of symptoms and signs is at times gradual, at times sudden. Chill and fever up to 40 degrees C occur during the acute stage, i.e. the period less than a month after parasite invasion. And a few weeks later, the chronic stage follows with the classical clinical features. In general, symptoms and signs can be classified as follows: mild, essentially symptomless, progressive, with irregular appetite, gastrointestinal disturbances, oedema, hepatomegaly, etc., and severe, with a syndrome associated with portal cirrhosis and hypertension. Pathogenic changes and complications are generally restricted to foci, but may eventually affect the whole liver. Calculi, acute suppurative cholangitis, recurrent pyogenic cholangitis, cholecystitis, hepatitis, and acute pancreatitis are important complications. Carcinoma of the liver is often found in association with clonorchiasis, too.