Pulmonary Vascular Enlargement on Computed Tomography: An Imaging Clue Favoring Viral Over Bacterial Infection

Background and Aims: Pulmonary vascular enlargement within affected lung parenchyma has been reported in viral pneumonia, particularly coronavirus disease 2019 (COVID-19), but comparative data on non-COVID viral and bacterial pulmonary infections remain limited. This study compared the frequency of pulmonary vascular enlargement between these two etiologic groups.
Methods: In this retrospective, single-center study, 111 adults with microbiologically documented viral or bacterial pulmonary infections and eligible non-contrast chest computed tomography (CT) scans were evaluated. Microbiological sampling was performed within ±5 days of CT. Pulmonary vascular enlargement was assessed qualitatively according to relative vessel caliber at a comparable branching level and loss of expected distal tapering. Group differences were evaluated, and logistic regression was performed with adjustment for age and sex.
Results: Pulmonary vascular enlargement was present in 25 of 57 viral infections (43.9%) and 7 of 54 bacterial infections (13.0%) (p<0.001). Viral infection was associated with higher odds of vascular enlargement (odds ratio [OR], 5.25; 95% confidence interval [CI], 2.03–13.58). The association persisted after adjustment for age and sex (adjusted OR, 4.83; 95% CI, 1.77–13.16; p=0.002). Intra-observer agreement was excellent (κ=0.889).
Conclusion: Pulmonary vascular enlargement was more frequent in non-COVID viral than in bacterial pulmonary infections. Although not pathogen-specific, this finding may provide an additional imaging clue when both viral and bacterial infections are considered.