Humans acquire clonorchiasis - infection by clonorchis
sinensis (Chinese liver fluke)- by eating raw or undercooked fish.
Adult worms are flat and transparent, live in the bile ducts, and pass
eggs to the intestine and the faeces.
After ingestion by an appropriate
snail, the egg hatches in a miracidium.
Cercariae escape from the
snail and seek out certain fish, which they penetrate and in which
they encyst.
When human hosts eat the fish the cercariae emerge in the
duodenum, enter the common bile duct through the ampulla of Vater, and
mature in the distal bile ducts to an adult fluke.
The symptoms vary
from mild to severe, depending on the number of flukes.
An onset with
chills and fever indicates bacterial infection from biliary
obstruction.
Patients with clonorchiasis may die from a variety of
complications, including biliary obstruction, bacterial cholangitis , pancreatitis, and cholangiocarcinoma.
With massive infection the liver may be up to three
times normal size.
Dilated bile ducts are seen through the capsule,
and the cut surface is punctuated with thick-walled, dilated bile ducts.
The flukes, sometimes in the thousands, can be expressed from the bile
ducts.
Microscopically, the epithelium lining the ducts is initially hyperplastic and then becomes metaplastic.
The surrounding stroma is
fibrotic.
Secondary bacterial infection is common and associated with
pus in the bile ducts.
Eggs deposited in the hepatic parenchyma are
surrounded by a fibrous and granulomatous reaction.
Masses of eggs
become lodged in the bile ducts and cause a cholangitis.
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The
pancreatic duct may also be invaded and become dilated, thickened,
lined by metaplastic epithelium, and eventually surrounded by scar.
The diagnosis is made by identifying the eggs of C. sinensis in
stools or in duodenal aspirates.
Treatment is with praziquantel.
Cholangiocellular carcinoma originating in either the
intra - or extrahepatic bile ducts, is a complication of clonorchiasis.
The similar liver fluke endemic in Thailand, Opisthorchis viverrini, also causes cholangiocellular carcinoma.
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