Incidental diagnosis of an asymptomatic hydatid cyst through low-grade 18F-FDG uptake in the peripheral rim

Abstract

Here we present a case of an untreated, asymptomatic, pulmonary hydatid cyst incidentally diagnosed on the basis of atypically low-grade 18F-FDG uptake in the peripheral rim and a minimal increase in uptake on dual-point 18F-FDG PET/CT. The patient underwent 18F-FDG PET/CT for characterization of a solitary lung lesion found on chest radiography and inconclusive findings on contrast-enhanced CT. Although the diagnosis was confirmed by a serum indirect hemagglutination assay positive for Echinococcus granulosus, the low-grade 18F-FDG uptake in the context of the asymptomatic presentation was noteworthy, as it could be related to minimal active inflammation. Our case, together with similar previously published findings, leads to the hypothesis that inflammatory 18F-FDG uptake may be an additional determinant of the cause of symptoms in these patients.