IS Case 527: Giardiasis

Justin Brucker, MD

University of Rochester

Imaging Sciences URMC 2010
Publication Date: 2010-09-11


Patient is a 23-year old male with recent diagnosis of HIV, presenting with several months of severe cramping, abdominal pain and watery diarrhea with occasional bloody stools, accompanied by a 30-lb. weight loss. Stool studies revealed Giardia duodenalis. One month after treatment, an upper GI series with small bowel follow-through was requested for persisting abdominal pain and diarrhea.


AP radiograph of the abdomen, taken after administration of barium oral contrast, demonstrated slightly thickened duodenal and jejunal folds and prominent micronodular appearance of the jejunal mucosa. Small bowel transit time was brisk.




Giardia duodenalis, also known as Giardia intestinalis and Giardia lamblia, is a widespread intestinal parasite that can cause chronic abdominal pain, watery diarrhea, and electrolyte disturbances. Humans and animals are typically infected via fecal-oral routes, when water or food contaminated by Giardial cysts is ingested. Trophozoites emerge in the GI tract and imbed within the mucosal gel layer, but do not invade the enterocytes. Several mechanisms of action have been proposed and include, but are not limited to: induced expression of proapoptotic genes, increased chloride secretion, inflammatory destruction of the enterocytes, and reduced brush border activity. The result is electrolyte/glucose loss and malabsorption. This leads to chronic, watery diarrhea. Immunocompromise is an obvious risk factor for infection [1].

Small bowel studies in patients with Giardiasis are often normal in appearance, but some cases will demonstrate signs of inflammation within the duodenum and proximal jejunum: thickened folds, villous atrophy, lymphoid hyperplasia, micronodularity. These findings are nonspecific, so definite diagnosis ultimately relies upon identification of Giardia cysts/trophozoites in the stool [2].


  1. Buret AG. Mechanisms of epithelial dysfunction in giardiasis. Gut. 2007 Mar;56(3):316-7. PMID: 17339241
  2. Gore RM, Levine MS. Textbook of Gastrointestinal Radiology, 3rd ed. Saunders, 2008; vol. 1, Chapter 46:810-811.

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