Giardiasis: diagnosis by endoscopic brush cytology of the duodenum.

The diagnosis of giardiasis is frequently difficult to make. The routine procedure of multiple stool examinations fails to detect Giardia lamblia trophozoites or cysts in 30-50% of cases. Small bowel biopsy and aspirate are believed to be the best way to make the diagnosis of giardiasis if the organism is not found in the stool and the diagnosis is still suspected. We describe two patients whose diagnosis of giardiasis was established by endoscopic brush cytology of the duodenal mucosa. The first patient had negative stool examinations, duodenal biopsy, and duodenal aspirate.