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Small bowel (small intestine)

Infectious disorders

Giardia lamblia

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 17 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Protozoan infection associated with malabsorption, chronic diarrhea
● Spreads by fecally contaminated water, common in underdeveloped countries
● Affects 1/3 of homosexual men in urban communities
● Attaches to mucosa but does not invade
● May cause endoscopic duodenal nodularity (Indian J Pathol Microbiol 2011;54:312)
● Causes epithelial barrier dysfunction by down regulating claudin 1 and increasing epithelial apoptoses (Gut 2007;56:328)

Life cycle


● Detect cysts, trophozoites or antigens in stool

Micro description

● Variable villous blunting, increased inflammatory cells, organisms are teardrop (pear) shaped with paired nuclei in lumen between villi
● Size of organism is similar to enterocyte nuclei

Micro images

Various images

Positive stains

● Trichrome with iron hematoxylin counterstain, Giemsa stain

End of Small bowel (small intestine) > Infectious disorders > Giardia lamblia

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