High magnification micrograph of a small bowel mucosa (duodenum) biopsy with giardiasis. H&E stain. Giardiasis is due to the flagellate protozoan Giardia lamblia.

The Giardia organisms are seen in the bowel lumen (bottom of image) and are:

• Pale staining/translucent.
• Size: 12-15 micrometers (long axis) x 6-10 micrometers (short axis) -- if seen completely.
• Most of the Giardia organisms seen are semicircular or crescent shaped -- as the long axis of the organism is rarely in the plane of the (histologic) section.

The villi have interepithelial lymphocytes, but have a normal architecture.

• Image:Giardiasis_duodenum_low.jpg - lower magnification view.