Incidental Giardiasis Diagnosed by EUS-FNA of a Lymph Node

Abstract

Introduction:Giardia lamblia is the most common protozoan causing diarrhea in the United States with a reported incidence of 4-7%. It is commonly diagnosed by identifying trophozoites and cysts in stool. Here, we present a case of incidental diagnosis of Giardiasis by transduodenal endoscopic ultrasoundguided fine needle aspiration (EUS-FNA). Case report: A 64-year-old man presented with painless jaundice. Laboratory evaluation showed elevated bilirubin (2.8 mg/dL), alkaline phosphatase (696 U/L), and CA 19-9 (125 U/L). MRI showed a long stricture of the common hepatic duct with a 2 cm hilar mass suggestive of a hilar cholangiocarcinoma. CT scans of the chest and abdomen showed no adenopathy or evidence for metastatic disease. The patient was referred for staging EUS for pre-liver transplant evaluation. EUS showed thickening of the common hepatic duct with a 15 mm x 12 mm hilar mass suggestive of a cholangiocarcinoma. Examination for lymphadenopathy revealed two small lymph nodes measuring 9 mm x 7 mm and 6 mm x 5 mm in the aortocaval space. FNA of the larger lymph node was performed using a 22 gauge needle, and 3 passes were made. Immediate on-site cytopathologic assessment of adequacy was made to ensure that the lesion was adequately sampled. Review of the specimen showed no evidence of malignancy; however, numerous pear-shaped, binucleated, flagellated organisms morphologically consistent with trophozoites of Giardia lamblia were identified. Final cytopathology examination confirmed parasitic organisms consistent with Giardia in a background of lymphocytes consistent with sampled lymph node. Given the candidacy for liver transplant the patient was treated with metronidazole. Discussion:Giardia enteritis typically leads to watery diarrhea, weight loss, and malabsorption but can also be asymptomatic. It is commonly diagnosed on examination of stool or duodenal aspirate by identifying Giardia trophozoites or cysts. The parasite commonly resides in proximal small intestine mainly duodenum with ileum, colon and jejunum being less common sites. The incidental finding of Giardia trophozoites on EUS-FNA has rarely been reported. In our case, Giardia was identified on a transduodenal FNA of an aortocaval lymph node in an asymptomatic patient representing duodenal contamination of FNA. This case highlights the importance of careful cytopathologic examination of FNA as Giardia can be easily missed.