Background:  The purpose of this study was to compare COVID-19 patients' vessel  caliber with that of normal lungs and lungs affected by other  inflammatory and thromboembolic processes.

Methods:   between March and April 2020, 42 patients affected by COVID-19  pneumonia (COV-P) underwent CT scans of the lungs at Verona University  Hospital for clinical indications. The lung images of four different  groups of patients were compared (normal lung (NL), distal  thromboembolism (DTE), and bacterial and fungal pneumonia (Bact-P,  Fung-P)) by a radiologist with four years of experience.

Results:  The COV-P patients' segmental and subsegmental vessels, evaluated  as the ratio with the corresponding bronchial branch (V/B ratio), were  larger, with respect to the NL the DTE groups, in the apparently healthy  parenchyma, a result confirmed in the zones of opacification with  respect to the Bact-P and Fung-P groups.

Conclusions:  This was the first study to show, by comparative analysis, that  COVID-19 patients' segmental and subsegmental vessel calibers are  significantly enlarged. This is a distinctive feature of COVID-19  pneumonia, suggesting its distinct pathophysiology as compared to other  inflammatory and thromboembolic diseases and alerting radiologists to  consider it when evaluating the CT scans of suspected patients.