Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Uptake of Jejunal Lymphocytosis Due to Giardiasis Mimicking Lymphoma Recurrence

A 49-year-old man, diagnosed with primary mediastinal B-cell lymphoma with pleural and nodal involvement in 2017, underwent chemotherapy and had a complete response [Figure 1]. Now, he presented with abdominal pain and vomiting and underwent contrast computed tomography (CT) abdomen which was normal. Fluorine-18 fluorodeoxyglucose positron emission tomography/CT (¹⁸F FDG PET/CT) whole body showed intensely hypermetabolic diffuse jejunal uptake, with no CT changes [Figure 2] and adjacent mesenteric lymph nodes. Push endoscopy showed normal mucosa till 20 cm past duodenojejunal flexure and underwent jejunal mucosal biopsy. Biopsy showed normal-appearing villi with a marked increase in intraepithelial lymphocytes and few teardrop (pear)-shaped organisms seen in the lumen between villi suggestive of giardiasis [Figure 3]. He was started on oral tinidazole 300 mg bd for 7 days and had good symptomatic relief.

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Figure 1 Maximum intensity projection positron emission tomography–computed tomography prechemotherapy, (a) Postchemotherapy, (b) Intensely hypermetabolic anterior mediastinal, left pleural lesions and lymph nodes showing complete metabolic response to therapy

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Figure 2 Maximum intensity projection (a), Axial (b), Coronal (c), Sagittal (d) Fused positron emission tomography–computed tomography showing intensely hypermetabolic diffuse FDG uptake in jejunum, with no CT wall thickening or lesions

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Figure 3 Photomicrograph of histopathological section showing intraepithelial lymphocytosis with pear-shaped organisms suggestive of giardiasis (H and E, ×400)

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Giardia lamblia, the etiological agent of giardiasis, is one of the most common intestinal protozoan flagellates in humans. Giardia species have a simple life cycle that consists of two active trophozoites and cystic forms. This parasite spreads through direct or indirect ingestion of infectious cysts via the fecal-oral route. Giardiasis affects both children and adults worldwide. Globally, more than 200 million cases of giardiasis are detected each year. Around about 200 million people in the world are with clinically manifested giardiasis.[1]

Ward et al. demonstrated nodular lymphoid hyperplasia of the upper small intestine in 25 patients with giardiasis. Seven patients initially presented with clinical findings suggestive of abdominal lymphoma and among that in only two patients, pathological diagnosis of primary jejunal lymphoma confirmed. It is possible that an etiological relationship exists between recurrent parasitic infestation and nodular lymphoid hyperplasia of the upper small intestine.[2] Shah et al. published a case of Giardia-filled pancreas mass who had chronic Giardia lamblia infection as a potential cause for transformation to T-cell-rich B-cell lymphoma manifestation.[3]

Pitfalls of small bowel PET/CT imaging primarily result from nonmalignant causes of increased FDG uptake. These include normal physiological uptake, uptake associated with inflammatory conditions such as Crohn’s disease and infectious, antibiotic-induced or radiation enteritis, and graft-versus-host disease. In general, tumors present as shorter-segment, more focal-intense lesions, while nonmalignant lesions are longer in length.[4] Nihashi et al. found FDG accumulation in the enteritis of the transverse to sigmoid colon. Colonoscopy revealed edematous, inflammatory, and punched out lesions in accordance with the areas of abnormal FDG uptake. A biopsy specimen showed the antibody of Cytomegalovirus in the colonic mucosa.[5] Our case is the first case of ¹⁸F FDG PET/CT image of jejunal giardiasis due to intraepithelial lymphocytosis mimicking lymphoma recurrence.