MRI appearance of COVID-19 pneumonia: an incidental finding

COVID-19 (coronavirus disease 2019) is an infectious disease
caused by severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2). The first cases was reported in Wuhan, China
on December 31st, 2019 and has rapidly spread globally.1
The main mode of transmission is person to person spread
via respiratory droplets during close contact. Clinical symptoms
are often nonspecific and include mainly fever and dry
cough, which may be accompanied by dyspnea, fatigue, myalgia
and headache.2 While most of the cases result in mild
to moderate symptoms, some progress to severe pnemonia
and acute respiratory distress syndrome (ARDS) leading to
death. The gold standart method of diagnosis is real-time reverse
transcriptase-polymerase chain reaction (rRT-PCR) test
on respiratory specimens, most frequently nasopharyngeal
swabs.3,4 However, the sensitivity of the rRT-PCR test depends
on specimen collection or viral burden at the time of
sampling and the initial tests may be negative.5 Therefore,
radiological imaging, particularly chest computerized tomography
(CT) which is a very sensitive imaging modality,
plays an important role in the diagnosis of COVID 19 pneumonia.
On chest CT, the typical and the earliest finding is the
unilateral or bilateral ground glass opacity (GGO) with peripheral
distribution predominantly in the lower lobes. With
the progression of the disease, extention of the GGOs with
multilobar involvement, with or without associated consolidation
and/or reticualtion (crazy paving patern) is seen.6
Considering the rapid spread of the infection, COVID-19
pnemonia can be encountered incidentally on any radiological
imagings which are performed for other reasons. In our
patient, COVID-19 pneumonia was recognised incidentally
on contrast enhanced MRI of the abdomen. He was a 47
year old male with a known history of primary malignant
disease, who underwent MRI in our outpatient clinic for the
evaluation of any suspicious metastatic lesions. At the time
of imaging, he had no clinical findings suggesting COVID 19 pneumonia and no history of close contact to a patient with
positive COVID 19 test. A patchy inhomogenous peripheral
pulmonary infiltration in the right lower lobe which was partially
covered on multiple sequences was demonstrated. It
was isointense on unenhanced T1w images and hyperintense
on T2w images (figure1). There was no diffusion restriction
(figure 2). Following intravenous contrast administration, the
infiltration showed mild enhancement which is more prominent
at the periphery of the lesion (Figure 3).
Probably it corresponds to the reversed halo sign (atoll sign)
shown on the targetted chest CT, which refers to complete
or incomplete ring-like consolidation surrounding a GGO.
It is a nonspecific pattern of organising pneumonia and has
also been reported in patients with Covid-19. The mechanism
of this sign is not clear. While some authers think that it depicts
disease progression that make consolidation developed
around GGO, others argue that it is related with absorption
in the lesion leaving a decreased attenuation in the center. On
the targetted chest CT, typical multifocal, patchy, peripherally
located GGOs were demonstrated (figure 4).
Diagnosis was confirmed by rRT-PCR test of an upper airway
smear. Although MRI is not an effective imaging modality
for the evaluation of pulmonary parenchyma due to
the low proton content of the lungs and possible respiratory
and cardiac pulsation artefacts, it has been shown to be an
important imaging modality that can be used, particularly
in the follow-up of patients who require dynamic imagings
to avoid exposure to ionising radiation.7 To our knowledge,
there are limited number of reports on the MRI findings of
COVID-19 pnemonia. In a retrospective case study, Vasilev
et al., concluded that MRI can be effectively used to detect
COVID 19 pneumonia especially in young people and in the
follow up imagings to avoid ionising radiation.8 Marcel et
al., reported a case with COVID 19 pneumonia recognized
incidentally on contrast enhanced MRI of the liver, similar to
our patient.9
In conclusion, COVID 19 pneumonia can be incidentally established
as peripherally located mild contrast enhancing
consolidations on MRIs, for example MRI of the upper abdomen
or thoracal spine. Therefore radiologists shoud be aware
of suspicious findings of COVID 19 pneumonia in all radiological
imaging modalities to allow early recognation of these
asypmtomatic carriers and prevent further transmission of
the infection.

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