FDG PET/CT Findings in an Asymptomatic Case of Confirmed COVID-19.

In the current and rapidly worsening pandemic, patients with COVID-19 may undergo imaging with FDG PET/CT. Because a significant proportion of infected patients may be asymptomatic, incidental discovery on a PET/CT scan performed for unrelated reasons can occur. Because of the highly infectious nature of this agent, it is important that interpreting physicians be aware of the typical imaging findings to identify potentially affected patients. We present the case of an asymptomatic patient referred for FDG PET/CT imaging of a lung nodule who demonstrated the typical CT findings of COVID-19 infection and was subsequently found to be positive on testing.

An asymptomatic 67-year-old man was referred for FDG PET/CT imaging for characterization of a suspicious lung nodule. MIP images (A) demonstrated numerous diffuse areas of increased uptake, involving all lobes, in addition to bilateral, hypermetabolic mediastinal lymphadenopathy. No significant metabolic abnormalities were noted outside of the thorax, in keeping with COVID-19’s suspected pulmonary tropism. Overall, these findings were consistent with the reported findings of suspected cases of COVID-19 infection seen on FDG PET/CT.[1] Despite being asymptomatic, given the imaging findings and the need for a subsequent biopsy of the lung nodule, the patient underwent testing, which confirmed COVID-19 positivity 7 days after PET/CT imaging. Axial PET, PET/CT, and CT images through the chest are shown (B–E). Images are arranged in descending order from the upper lobes (B), the mid-lung level (C and D), to the lower lobes (E). The patient lung nodule (SUV, 4.1) is seen in the right lower lobe (E, arrow). The typical findings of COVID-19 infection are seen on the CT, including bilateral and peripheral ground-glass and consolidative pulmonary opacities,[2-8] present in all lobes. PET/CT images demonstrate relatively intense uptake (SUVs ranging from 5.0 to 7.2) in the peripheral opacities. Despite the presence of significant abnormalities on both CT and PET/CT images, the patient was asymptomatic at the time of the study—this incongruency between clinical presentation and imaging features has previously been reported in the CT literature.[5,9,10] Although mediastinal lymphadenopathy was evident on PET/CT images (B–D), no lymph nodes were size significant, in keeping with the reported findings on both PET/CT and CT.[1,8] Despite the presence of a malignant lesion in the right lower lobe (a biopsy proven adenocarcinoma), the distribution of mediastinal lymphadenopathy (ie, bilateral hila), as well as their small size, was more suggestive of reactive lymph nodes than metastatic disease. This case demonstrates findings of an FDG PET/CT in an asymptomatic case of confirmed COVID-19 infection. The features of this case are concordant with and confirm those presented in a previous report on the FDG PET/CT findings in symptomatic patients with suspected infections. Furthermore, this case reiterates the fact that asymptomatic patients may demonstrate evident signs of infection on imaging, on both PET/CT and CT. In light of the highly contagious nature of this illness, and its rapidly increasing prevalence, it is likely that additional cases will be incidentally discovered on asymptomatic patients undergoing PET/CT imaging, and it will be incumbent on the interpreting physician to recognize the significance of the imaging findings despite the lack of clinical symptoms. Hopefully, familiarity with these findings should facilitate this.