Paragonimus westermani and Clonorchis sinensis Eggs
Bench-card visuals for lung and liver trematode eggs: Paragonimus westermani (large, golden-brown, operculated with shouldered rim) found in sputum or stool, and Clonorchis sinensis (tiny flask-shaped, operculated with prominent shoulders and abopercular knob) found in stool.
Trematode eggs: Paragonimus (large, shouldered) vs. Clonorchis (tiny, vase-shaped)
Paragonimus westermani: 80-120 x 45-60 um - large, ovoid, golden-brown, shouldered opercular rim, thickened abopercular shell. In sputum (rust-colored) or stool. Clonorchis sinensis: 28-34 x 12-19 um - very small, flask-shaped, ye...
80-120 x 45-60 um. Large, broadly ovoid, golden-brown. Shouldered operculum - the egg wall thickens and forms a rim (shoulder) where the operculum meets the shell; the operculum appears to sit in a groove. Abopercular shell is notably thickened. Unembryonated when passed (uniform granular content). Found in: sputum (characteristic rust-colored hemoptysis) or stool (if sputum swallowed). Lung fluke - acquired by ingestion of raw or undercooked freshwater crabs or crayfish.
28-34 x 12-19 um. Very small - the smallest common trematode egg. Flask or vase-shaped (narrow at opercular end, widening toward the middle). Yellow-brown. Prominent opercular shoulders (inner ridge clearly visible at opercular rim - diagnostic). Small knob at the abopercular end. Embryonated (miracidium inside) when passed. Found in stool. Bile duct fluke - acquired from raw or undercooked freshwater fish. Opisthorchis viverrini (Southeast Asia) is morphologically identical.
80-120 x 45-60 um. Large, broadly ovoid, golden-brown. Shouldered operculum - the egg wall thickens and forms a rim (shoulder) where the operculum meets the shell; t...
28-34 x 12-19 um. Very small - the smallest common trematode egg. Flask or vase-shaped (narrow at opercular end, widening toward the middle). Yellow-brown. Prominent...
Trematode egg differential - what to look for
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Large ovoid egg, 80-120 um, shouldered operculum, golden-brown, thickened abopercular shell | Paragonimus westermani | Largest common trematode egg in sputum; shouldered operculum + abopercular thickening = diagnostic pattern |
| Small flask-shaped egg, 28-34 um, prominent opercular shoulders, abopercular knob | Clonorchis sinensis or Opisthorchis spp. | Smallest common trematode egg; prominent shoulders + tiny knob at both poles; requires concentration method and high-power exam |
| Rust-colored sputum + operculated egg | Paragonimus - paragonimiasis | Rust-colored "coffee-ground" hemoptysis is characteristic; examine both sputum and stool for eggs |
| Operculated egg, 58-76 um, no pronounced shoulder | Diphyllobothrium latum (cestode, not trematode) | D. latum: operculated, yellowish-brown, smooth rim without shoulder, small knob - rule out by size and shoulder absence |
| Very large operculated egg, 130-150 um, no shoulder | Fasciola hepatica (sheep liver fluke) | Fasciola eggs are larger than Paragonimus and lack the shouldered opercular rim; geographic exposure to sheep pastures or watercress |
Trematode egg identification guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Large ovoid 80-120 um, shouldered opercular rim, abopercular thickening | Paragonimus westermani - positive | Report with specimen source (sputum or stool); praziquantel treatment; clinical correlation and imaging recommended |
| Small flask-shaped 28-34 um, prominent opercular shoulders, abopercular knob | Clonorchis sinensis or Opisthorchis spp. | Report with geographic context; praziquantel treatment; liver function tests and biliary imaging recommended |
| Operculated egg not matching above patterns | Trematode egg - consult reference table | Measure carefully; consult species-specific size table; consider Fasciola (larger, no shoulder), D. latum (no shoulder, cestode) |
- Paragonimus: large 80-120 um, golden-brown, shouldered opercular rim + thickened abopercular shell - in sputum or stool.
- Clonorchis: tiny 28-34 um, flask-shaped, prominent opercular shoulders + abopercular knob - smallest common trematode egg.
- Fasciola (130-150 um) is larger than Paragonimus and lacks the shouldered rim - the largest common operculated trematode egg.
Paragonimus: large, shouldered, in sputum or stool. Clonorchis: tiny, vase-shaped with knob. Fasciola: largest operculated egg, no shoulder.