A 32-year-old man returns from trekking with foul smelling, bulky stools, bloating, and excessive flatulence. Stool microscopy shows pear shaped trophozoites with two nuclei, four pairs of flagella, and a 'falling leaf' motility. Which structure mediates attachment of this parasite to the duodenal mucosa?

• A Cytostome
• B Undulating membrane
• C Axostyle
• D Ventral adhesive disc ✓

Explanation

Giardia lamblia trophozoites attach to duodenal enterocytes using the ventral adhesive (sucking) disc, producing malabsorption with steatorrhoea. Diagnosis rests on cysts or trophozoites in stool, or on stool antigen ELISA which is more sensitive. The undulating membrane and axostyle are structures of Trichomonas vaginalis, which also lacks a cyst stage, making them the tempting wrong choices. The 'falling leaf' motility of live trophozoites in a wet mount is a classic examination finding.

Reference: Paniker's Textbook of Medical Parasitology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.