Question

Which of the following may cause biliary obstruction?

• A. Ancylostoma
• B. Enterobius
• C. Strongyloides
• D. Clonorchis

Hint:

Which of these is a liver fluke that lives inside the bile ducts?

Answer 1

The Correct Option is D

To answer this, match each worm to the organ it occupies and decide which one can plug the bile drainage. The key idea is that only a fluke that physically dwells in the bile ducts can obstruct them. Among the four choices, Clonorchis sinensis is the Chinese liver fluke, and adult worms reside inside the intrahepatic biliary radicles. Their bodies and eggs trigger duct wall thickening, periductal fibrosis and mechanical blockage, and long-standing infection is a known driver of bile duct cancer. That fits the question perfectly. The other three are gut-dwellers with no biliary home. Hookworm (Ancylostoma) clamps onto the duodenal and jejunal mucosa and bleeds the patient into anaemia. Pinworm (Enterobius) settles in the large bowel and causes nocturnal anal itch via perianal egg laying. Strongyloides occupies the upper small intestine, with a self-sustaining autoinfective cycle and risk of disseminated hyperinfection, again nowhere near the bile ducts. So the single parasite that explains biliary obstruction is the liver fluke. $D$ is the answer. \[\boxed{\text{Clonorchis}}\]