Incidental COVID-19 Pneumonia on Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography: The “New-normal”

Sir,

The coronavirus disease 2019 (COVID-19) pandemic is sweeping through the globe with >3.5 million cases and 0.25 million deaths at the time of writing this article.[1] While India has been able to stall rapid progression of cases till now, it is likely that the infection will creep through the population over time until a vaccine is available. It has been reported that >80% of those infected have no or minimal symptoms and hence may remain undetected and untested. Also, while the specificity of the currently available reverse transcription-polymerase chain reaction (RT-PCR) test being used to confirm the infection is very high, the sensitivity is modest at ~70%.[2] Hence, it is quite likely that we will incidentally keep seeing such undetected/asymptomatic cases during routine clinical positron emission tomography-computed tomography (PET-CT) scanning. In many instances, such as patients with underlying advanced cancers, the symptoms may be masked or not looked for. Therefore, it is vital that we maintain a high index of suspicion when evaluating clinical PET-CT images to not miss COVID-19 findings.

COVID-19 being a pulmonotropic virus, the findings are usually limited to lungs with possible secondary changes in draining nodes. The classical findings are peripheral ground-glass opacities (GOO's) and peripheral consolidations, predominantly involving the lower lobes, with the absence of pleural effusion.[3] Increased fluorodeoxyglucose (FDG) uptake can be seen in the above lesions with uptake varying from mild to high. Significant lymph node enlargement is usually not seen, but increased FDG uptake in draining nodes might be seen. However, we must remember that manifestations of underlying diseases such as cancer or renal failure might complicate the imaging findings. Pleural effusion or pulmonary edema or aspiration pneumonia can impair our imaging judgment. I would present two such cases of incidental COVID-19 pneumonia detected on FDG PET-CT, which we encountered in our clinical practice.

The first patient, a 44-year-old male, had a history of fever for 2 weeks. He was a known case of end-stage chronic kidney disease V and waiting for transplantation. He had a history of recurrent bilateral pleural effusion, more marked on the left side, which was drained twice and was negative for infection. A HRCT chest done 5 days back showed only effusion. FDG PET-CT was done for fever workup [Figure 1], which showed bilateral pleural effusion (b and c, *) and liver lesion suspicious for an abscess (d and e, bold arrow). Also seen was bilateral lung minimally FDG-avid ground-glass opacities with few focal subpleural consolidations (b and c, arrows), raising suspicion of COVID-19 pneumonia. A RT-PCR test from nasal swab was positive for COVID-19. The lives lesion showed pyogenic abscess with the growth of Gram-negative bacteria. The second patient, a 58-year-old female, known case of gastric adenocarcinoma with bone metastases, underwent FDG PET-CT [Figure 2] for assessing chemotherapy response. Bilateral lung mildly FDG avid ground-glass opacities with few focal subpleural consolidations (b and c, arrows) were seen, raising suspicion of COVID-19 pneumonia. Non FDG-avid calcified mediastinal and hilar nodes were seen (d, bold arrows), sequel of prior granulomatous infection. Bilateral mild pleural effusion was also seen (b and c, *). Also seen were residual mildly FDG avid sclerotic bone metastases (e). RT-PCR test from nasal swab was positive for COVID-19. She passed away 5 days later due to complications of COVID-19 pneumonia. These cases highlight that incidental detection of COVID-19 pneumonia in routine PET-CT practice will become the new normal in the foreseeable future, and we need to be vigilant so as to not miss these findings. Also, the findings will always not be textbook perfect and may be overlapped by the sequel of underlying non-COVID-19 pathology.

Close

Figure 1

The first patient, a 44 year old male, with CKD, presented with fever. Fluorodeoxyglucose positron emission tomography-computed tomography was done for fever workup (a) which showed bilateral pleural effusion (b and c,*) and liver lesion suspicious for an abscess (d and e, bold arrow). Also seen was bilateral lung minimally fluorodeoxyglucose avid ground glass opacities with few focal subpleural consolidation (b and c, arrows), raising suspicion of corona virus disease 2019 pneumonia

Export to PPT

Close

Figure 2

The second patient, a 58 year old female, known case of gastric adenocarcinoma with bone metastases, underwent fluorodeoxyglucose positron emission tomography-computed tomography (a) for chemotherapy response. Bilateral lung mildly fluorodeoxyglucose avid ground glass opacities with few focal subpleural consolidations (b and c, arrows) were seen, raising suspicion of corona virus disease 2019 pneumonia. Non fluorodeoxyglucose avid calcified mediastinal and hilar nodes were seen (d, bold arrows), sequel of prior granulomatous infection. Bilateral mild pleural effusion was also seen (b and c, *). Also seen were residual mildly fluorodeoxyglucose avid sclerotic bone metastases (e)

Export to PPT