key: cord-1021726-9bgbwdoi
authors: Piciucchi, S.; Ravaglia, C.; Vizzuso, A.; Bertocco, M.; Poletti, V.
title: Reversibility of venous dilatation and parenchymal changes density in Sars-Cov-2 pneumonia: toward the definition of a peculiar pattern
date: 2020-11-16
journal: Pulmonology
DOI: 10.1016/j.pulmoe.2020.10.010
sha: ed63a9a825db261fb9b302d5b3922624f0f46347
doc_id: 1021726
cord_uid: 9bgbwdoi

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regions, beside the typical aspects of ground glass attenuation and consolidations . These features were labeled as "hyperemic halo" pattern (4) . Here we describe CT findings of five patients affected by COVD-19 in the early phase of the disease emphasizing the vascular and alveolar changes modified by the gravity.

Five subjects with a diagnosis of COVID-19 based on nasal swab test underwent CT scan in supine and later in the same session the prone position. CT protocol consisted of two consecutive acquisitions respectively in supine and prone position, the latter during administration of contrast medium, with a protocol able to opacify pulmonary both arteries and pulmonary veins.

Clinical and laboratory profiles are summarized in Tab 1.

In all the five cases, pulmonary veins were patent. Other radiological features for each patient was as follows:

Case 1: 78 years-old male. In the supine position, focal pure ground glass opacities were present in both upper lobes, and some peripheral part-solid ground glass areas with a coexisting crazy paving attenuation in both costophrenic angles. Furthermore, the peripheral branches of the pulmonary veins of the lower lobes appeared enlarged. In the prone position a significant decrease in diameter of veins and a kind of parenchymal ground glass attenuation in both lower lobes. Moreover, a rapid reduction of the density was observed in the "former crazy paving component" that changed into pure ground glass attenuation ( Fig.1) Case 2: 64-year-old male. Subsegmental pulmonary arteries defects were present in the right lower lobe.

Pulmonary veins showed a relative reduction in caliber in the prone positioning. The relevant observations of this series are: the enlarged vessels are pulmonary veins; the diameter of these enlarged vessels and the density of ground glass and/or crazy paving areas pouring in them decrease when they are no longer in the dependent zones.

These findings were detected in patients with an early and mild-to moderate form of disease supporting the hypothesis that a large part of the ground glass attenuation/crazy paving pattern could be due to the neoangiogenesis taking place in the alveolar septa instead of accumulation of proteinaceous edema and hyaline membranes in the alveolar spaces (3) .

The "bandlike" opacities described in Covid-19 pneumonia are reversible in the prone position, suggesting again the presence of lung parenchymal vascular gravity-dependent changes (4) .

Furthermore, dilatation of the lumen of the pulmonary veins reversed by pronation could be related to dysregulation of their muscular tone induced by substances produced in the areas with ground glass/crazy paving opacification and released in the blood flow (6) (7) .

The significant increase of oxygen saturation after pronation observed in patients with early stage of COVID-19 interstitial pneumonia might not actually reflect the recruitment of previously atelectatic alveoli, as observed in cases in which interalveolar edema, hyaline membranes and loss of alveolar stability are the histopathologic background, but rather the reduction of the "dead space" and "shunt" effects related to pulmonary capillary and venous blood redistribution induced mainly by gravity changes (7) .

In conclusion in this series we suggest that intra-alveolar capillary hyperplasia could be the main anatomic background of ground glass/crazy paving opacification, and hypothesize a link between veins enlargement, ground glass/crazy paving opacification and the pathophysiology profile observed in the early phase of the disease. We labelled all these features "venoplegic/hyperemic pattern". In the right lower lobe a part-solid ground glass attenuation with a coexisting minimal crazy paving pattern, is present beneath the pleura (c; red ellipse) in the apical and postero-basal segments.

Some vessel enlargement is present in both lower lobes. In the right lower lobe, the enlargement is both outside and inside the GG attenuation and involves branches of the pulmonary veins (caliber of 4.6 mm).

Finally, in the left lower lobe, a nodular consolidation is present, adjacent to the pleura (pink arrow), with a drastic reduction in density with the prone positioning. 

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