What is the role of endoscopy and biopsy in the diagnosis of giardiasis?

Updated: Oct 01, 2018
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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Esophagogastroduodenoscopy (EGD) may be employed in patients in whom the diagnosis is suspected but unproven after stool microscopy and ELISA. This also may be used for patients who continue to manifest symptoms of malabsorption after adequate therapy.

Endoscopy may be used to assess the small bowel architecture and obtain a duodenal aspirate or biopsy. While rarely necessary, duodenal biopsy may be the most sensitive test. This has several benefits over the string test. An aspirate can be cultured to assess for overgrowth of the small intestine. Other small bowel parasites, such as microsporidia and cryptosporidia, may be detected in biopsy samples. Spruelike lesions, which may occur with giardiasis, can be detected with this technique.

Biopsy can also be used to visualize changes in histologic features. Intestinal biopsy shows flattened, mild lymphocytic infiltration and trophozoites on the surface. [22, 29]

Biopsy specimens from duodenum are often teeming with sickle-shaped Giardia trophozoites, which are tightly bound by the concave attachment disc to the villus surface of the intestinal epithelial cells. In cases where trophozoites are difficult to recognize in biopsy samples, specific anti-Giardia immunoperoxidase stains aid in the detection of the organisms, although these stains are not readily available.

Many patients exhibit atrophy of the small intestinal villi with a mixed inflammatory infiltrate in the lamina propria. The brush borders of the surface absorptive epithelial cells are irregular, and virtual absence of villi may be noted, as in celiac disease.

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