When pneumonia is not COVID-19

Abstract

During the COVID-19 epidemic, the prevalence of the disease means that practically any lung opacity on an X-ray could represent pneumonia due to infection with SARS-CoV-2. Nevertheless, atypical radiologic findings add weight to negative microbiological or serological tests. Likewise, outside the epidemic wave and with the return of other respiratory diseases, radiologists can play an important role in decision making about diagnoses, treatment, or preventive measures (isolation), provided they know the key findings for entities that can simulate COVID-19 pneumonia. Unifocal opacities or opacities located in upper lung fields and predominant airway involvement, in addition to other key radiologic and clinical findings detailed in this paper, make it necessary to widen the spectrum of possible diagnoses.

Keywords: COVID-19; Computed tomography; Diagnostic imaging; Radiography; X ray; X-rays.

Figure 2

Pulmonary diseases with clinical and pathological confirmation that occur in characteristic clinical contexts, but are similar in appearance to COVID-19 pneumonia. A) Differentiation syndrome secondary to treatment with tretinoin in a patient with acute promyelocytic leukaemia showing bilateral consolidations associated with some areas of ground-glass attenuation and nodular opacities. B) Exogenous lipoid pneumonia manifesting as dense ground-glass areas of attenuation at both lung bases. C) Patient with suspected COVID-19 ultimately diagnosed with pulmonary thromboembolism with pulmonary infarction, which exhibited an inverted halo and a filling defect in the left lower lobe branch, shown in the sagittal reconstruction (arrows).

Figure 1

Computed tomography (CT) images corresponding to 2 patients with lesions featuring a similar radiological appearance: A) A 40-year-old woman with limited systemic sclerosis and cough, with persistent lung consolidation in the left lower lobe for more than 9 months and a pathology diagnosis concordant with inflammatory pseudotumour. B) A 52-year-old man who presented during the COVID-19 pandemic with a persistent high fever and dyspnoea for 4 days. As his symptoms persisted following a negative PCR test, a CT scan was performed that showed a consolidation similar in appearance to image A, finally diagnosed with SARS-CoV-2 pneumonia after confirmation by another PCR test.

Figure 3

A 39-year-old man who presented during the pandemic with asthenia, myalgia and odynophagia, with a final diagnosis of pulmonary tuberculosis. A chest X-ray (A) showed extensive bilateral consolidations, predominantly upper and central on the right side and in upper and middle fields on the left side, with possible cavitations confirmed in the coronal CT reconstruction (B). Opacities with a tree-in-bud morphology and some lesions with an inverted halo appearance are also visible; their micronodular edges are a distinctive characteristic of the disease (arrows in C).

Figure 4

A 42-year-old man with no history of note who presented during the pandemic with fever and dyspnoea lasting 3 weeks accompanied by hypoxaemia, lymphopenia and elevated D-dimer and LDH. A chest X-ray (A) showed pulmonary opacities, predominantly perihilar and in the upper two-thirds of the lungs, with small cystic images on the left side. CT angiography to rule out pulmonary thromboembolism (B and C) showed the presence of ground-glass attenuation opacities with a slightly greater predominance and a tendency to spare the lung periphery, accompanied by thin-walled air-cyst lesions. Pneumocystis jirovecii pneumonia was suspected; it was confirmed by bronchoalveolar lavage. Later, the patient tested positive for human immunodeficiency virus.

Figure 5

Radiological findings in cases of pneumonia with an aetiology other than COVID-19. A) Lobar consolidation in Streptococcus pneumoniae pneumonia. B) Peribronchovascular “clustered” opacities caused by respiratory syncytial virus. C) Branched opacities with a tree-in-bud morphology in influenza A virus infection D) Peribronchovascular consolidation in bilateral influenza A virus pneumonia E) Cobblestone pattern in Streptococcus pneumoniae pneumonia.

Figure 6

Computed tomography, performed during the pandemic in an elderly man with fever and a fluctuating level of consciousness, showing bilateral posterobasal consolidations with subpleural sparing. Aspiration was suspected. Clinical and radiological signs and symptoms resolved with antibiotics, and COVID-19 was ruled out during admission.

Figure 7

A 34-year-old woman, a multi-drug addict, who presented during the pandemic with fever, dyspnoea and hypoxaemia, as well as elevation of D-dimer. A portable chest X-ray (A) showed extensive bilateral consolidation. Pulmonary CT angiography was performed (coronal reconstruction in B; axial image in C) that showed a diffuse cobblestone pattern, with a central predominance and no pleural effusion. As non-cardiogenic pulmonary oedema due to drugs was suspected, the patient was treated with corticosteroids, with rapid complete resolution of clinical and radiological signs and symptoms at 24 hours (D), which is characteristic of the disease. The patient had presented a similar clinical picture one month earlier with an identical outcome.

Figure 8

Interstitial diseases similar in appearance to COVID-19 that may manifest with dyspnoea and occasionally fever. A) Cryptogenic organising pneumonia with peripheral consolidation and air bronchogram. B and C) Non-specific interstitial pneumonia showing areas of ground-glass attenuation and peripheral consolidation with a subpleural-sparing band. D) Desquamative interstitial pneumonia in a patient who smokes, showing extensive areas of ground-glass attenuation and small air cysts. E) Chronic eosinophilic pneumonia showing peripheral consolidation partially sparing the subpleural region and characteristically affecting the upper lobes.

Figure 9

Pneumonitis secondary to drug toxicity. Its clinical presentation and parenchymal changes can simulate COVID-19 pneumonia. A) Patient with colon carcinoma being treated with the FOLFOX regimen (folinic acid, fluorouracil and oxaliplatin). B) Renal cell carcinoma treated with everolimus. C) Patient with lung neoplasm with ALK mutation treated with alectinib, who presented during the pandemic with dyspnoea; COVID-19 and other causes of the lesions were ruled out.