A 22-year-old man returns from a Himalayan trek complaining of 3 weeks of greasy, foul-smelling stools, bloating, excessive flatus and 4 kg weight loss. There is no fever and no blood in the stools. Stool microscopy shows pear-shaped trophozoites with two nuclei. Which organism is responsible?
- A Entamoeba histolytica
- B Giardia lamblia ✓
- C Cryptosporidium parvum
- D Cyclospora cayetanensis
Correct answer: B. Giardia lamblia
Explanation
Giardia lamblia attaches to duodenal and jejunal epithelium without invading, producing malabsorption with steatorrhoea, foul flatus and weight loss, classically without fever or bloody stool. Entamoeba histolytica causes invasive colitis with bloody dysentery and fever, which kills the most tempting distractor. Cryptosporidium causes profuse watery diarrhoea mainly in immunocompromised hosts rather than steatorrhoea.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.