[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Trematodes (flukes)](https://durgical.com/en/microbiology/groups/trematodes/) › Clonorchis sinensis / Opisthorchis spp.

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# Clonorchis sinensis / Opisthorchis spp.

- Parasite
- For completeness

Liver flukes from raw freshwater fish in Asia. They live for years in the bile ducts and raise the risk of bile duct cancer.

Updated 2026-11-01

Also called: Chinese liver fluke, opisthorchiasis, clonorchiasis

## Key points

- Raw freshwater fish in Asia.
- Lives in the bile ducts.
- Risk factor for cholangiocarcinoma.
- Small egg with an operculum on shoulders.
- Praziquantel.

## At a glance

**Shape**
Lancet-shaped, flat and translucent

**Family**
Opisthorchiidae

**Type**
Hepatic trematode (bile duct fluke)

**Size**
Adult 1–2.5 cm

## Morphology

- Small egg (27–35 µm) with a convex operculum resting on 'shoulders'.
- Small knob at the opposite end; passed already embryonated.
- Clonorchis and Opisthorchis eggs are practically indistinguishable.

## Transmission

- Eating raw, salted, pickled or smoked freshwater fish with metacercariae.

**Reservoir:** Humans, dogs, cats and other fish-eating mammals; Freshwater snails and fish as intermediate hosts

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- Embryonated eggs leave in stool and bile; a freshwater snail swallows them.
- Inside the snail they multiply and cercariae are released into the water.
- Cercariae penetrate freshwater fish and encyst in their flesh as metacercariae.
- A person who eats that fish raw, salted or smoked releases the metacercaria in the duodenum.
- It climbs through the ampulla of Vater to the bile ducts, matures in a month and lives for years.

## Virulence factors

- Chronic inflammation causes biliary epithelial hyperplasia and periductal fibrosis.
- Promotes stones, recurrent cholangitis and abscesses.
- C. sinensis and O. viverrini are classified as carcinogens: cholangiocarcinoma.

## Diseases it causes

- Cholangiocarcinoma linked to chronic infection [Cholangiocarcinoma (bile duct cancer) →](https://durgical.com/en/conditions/cholangiocarcinoma/)
- Acute cholangitis and bile duct stones [Acute cholangitis →](https://durgical.com/en/conditions/acute-cholangitis/)

## Clinical picture

- Light infections are asymptomatic.
- Heavy loads: fever, right upper quadrant pain, hepatomegaly.
- Obstructive jaundice or a biliary mass after years of infection.

## Diagnosis

- Small eggs with a shouldered operculum on stool microscopy.
- Serology in specialised laboratories.
- Ultrasound or MRCP: dilated bile ducts.
- Adults found at surgery or after treatment.

## Treatment

Praziquantel is the drug of choice; albendazole is an alternative.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Praziquantel](https://durgical.com/en/pharmacology/praziquantel/)

## Prevention

- Cook freshwater fish thoroughly.
- Avoid raw freshwater fish dishes in endemic areas.
- Sanitation so that faeces do not reach ponds and rivers.

## In Colombia

Not native to Colombia; seen in migrants or travellers from East and Southeast Asia.

## Memory aid

Raw Asian river fish, flukes in the bile, cancer down the road: three steps from plate to bile duct.

## Test yourself

Think of the answer, then tap the question to see it.

## Which cancer is linked to Clonorchis sinensis and Opisthorchis viverrini?

Cholangiocarcinoma.

## How is clonorchiasis acquired?

By eating raw, salted, pickled or smoked freshwater fish with metacercariae.

## What is the drug of choice for clonorchiasis?

Praziquantel.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/clonorchis-sinensis-opisthorchis-spp/)

## Related

- [Fasciola hepatica](https://durgical.com/en/microbiology/fasciola-hepatica/)
- [Paragonimus spp.](https://durgical.com/en/microbiology/paragonimus-spp/)

## Related conditions

- [Cholangiocarcinoma (bile duct cancer)](https://durgical.com/en/conditions/cholangiocarcinoma/)
- [Acute cholangitis](https://durgical.com/en/conditions/acute-cholangitis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Trematodes (flukes)](https://durgical.com/en/microbiology/groups/trematodes/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [CDC - DPDx - Clonorchiasis](https://www.cdc.gov/dpdx/clonorchiasis/index.html) (CDC, 2024); [Foodborne trematode infections](https://www.who.int/news-room/fact-sheets/detail/foodborne-trematode-infections) (WHO, 2021).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/clonorchis-sinensis-opisthorchis-spp/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/clonorchis-sinensis-opisthorchis-spp/