Small intestine & ampulla

Infectious disorders

Giardia lamblia

Topic Completed: 1 August 2012

Minor changes: 17 February 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Giardia lamblia[TI] small bowel[mh]

Hanni Gulwani, M.B.B.S.
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Cite this page: Gulwani H. Giardia lamblia. website. Accessed October 15th, 2021.
Definition / general
  • 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 claudin1 and increasing epithelial apoptoses (Gut 2007;56:328)
Diagrams / tables

Images hosted on other servers:

Life cycle

  • Detect cysts, trophozoites or antigens in stool
Gross images

Contributed by Centers for Disease Control and Prevention


Microscopic (histologic) 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
Microscopic (histologic) images

Contributed by Bobbi Pritt, M.D. and Emily Fernholz

Trichrome stained stool specimen, Giardia duodenalis

Contributed by Bobbi Pritt, M.D.


Case #157

Giardial trophozoites
along the surface of
foveolar epithelial cells

Sickle shaped trophozoites

Positive stains

"Falling leaf" motion of trophozoite

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