Low grade FDG uptake on the rim of “doughnut” in PET-CT in an asymptomatic Hydatid cyst: is inflammatory activity a determinant of symptoms?

Abstract

Herein we present an untreated asymptomatic incidentally diagnosed suspected case of pulmonary hydatid cyst with its atypically low grade ¹⁸F-FDG uptake on the peripheral rim of the cyst with minimal increase on dual point imaging of ¹⁸F-FDG- PET-CT. The patient underwent ¹⁸F-FDG-PET/CT for characterization of solitary lung lesion on chest X-ray and inconclusive ceCT features. While the diagnosis was confirmed by serum IHA positive for echinococcus granulosus, the low grade ¹⁸F-FDG uptake in the context of asymptomatic presentation of the disease is noteworthy, that could be related to minimal active inflammation. When placed in context of similar published reports, it could be hypothesized that the inflammatory ¹⁸F-FDG uptake could be an additional determinant of symptoms in this group of patients.