A 30-year-old woman from Rajasthan presents with a hepatic cyst on ultrasound; serology is positive for Echinococcus granulosus by IHA (titre 1:320). Fine needle aspiration is deferred. She is prescribed albendazole. Which laboratory finding in the cyst fluid, if aspirated inadvertently, would be PATHOGNOMONIC for hydatid disease?

• A Turbid fluid with elevated LDH and degenerated cells
• B Elevated CA 19-9 in the cyst fluid
• C Scolices (protoscolices) with hooklets and calcareous corpuscles under microscopy ✓
• D Eosinophilia >40% in cyst fluid differential count

Explanation

The pathognomonic finding in hydatid (echinococcal) cyst fluid is the presence of protoscolices with rostellar hooklets and calcareous corpuscles — the so-called 'hydatid sand.' This directly demonstrates the larval stage of Echinococcus granulosus. Eosinophilia in cyst fluid is non-specific. CA 19-9 elevation may occur in benign hepatic cysts and biliary disease. Turbid fluid with elevated LDH is characteristic of abscess or neoplasm, not hydatid disease.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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