key: cord-0991233-atbz1hxs
authors: Sefidbakht, S.; Iranpour, P.
title: Comment on: COVID-19 or Pulmonary Contusion? A Diagnostic Dilemma
date: 2020-05-13
journal: Acad Radiol
DOI: 10.1016/j.acra.2020.05.002
sha: 2ed2a23e0cdbe19090e2908bc9b8beea6c5e054f
doc_id: 991233
cord_uid: atbz1hxs

nan

Sefidbakht S. 1 Funding Sources/Disclosures: Authors. report no conflict of interest or funding sources. Consent: Images are completely anonymized, however informed consent has also been obtained from the patient.

We reviewed with interest the recent article titled "COVID-19 or Pulmonary Contusion? A Diagnostic Dilemma" (1). The article underscores the importance of concomitant COVID-19 infection in traumatic patients and discusses some radiologic findings to facilitate the differentiation of the two entities. Diagnosing a patient as potential COVID-19 has major implications in hospital management and bed allocation. Inadvertently labeling a patient as COVID-19 or potential COVID-19 can result in admission to a COVID-19 ward and thus increasing the risk of infection to the patient. On the other hand, timely diagnosis of COVID infection in an asymptomatic or pre-symptomatic case of trauma significantly reduces the chance of transmission to the medical staff and other patients, and also may influence the prognosis and reduce morbidity and mortality. We thus find the article of utmost value and significance in the current pandemic.

Authors have stated that "pulmonary contusion is associated with laceration and gas accumulation in the lung parenchyma". We would like to make a further distinction between pulmonary contusion and laceration. According to the more recent studies, pulmonary contusion is defined as damaged alveolar capillaries, as the result of blunt trauma, explosion injuries, or shock wave associated with penetrating trauma (2) . Such endothelial injury is associated with the accumulation of blood and other fluids in the lung tissue, and contrary to laceration, there is no cut or a tear of the lung tissue. On the other hand, post-traumatic cavitary lesions, also referred to as traumatic pulmonary pseudocysts, following blunt trauma, occur as the result of the compression-decompression mechanism, leading to local lacerations in the lung parenchyma (3).

Secondly, subpleural sparing has been proposed as a possible differentiating radiologic sign. Fig 1  demonstrates an axial CT image of a PCR-confirmed nontraumatic COVID pneumonia with typical subpleural sparing at least in some parts. We have observed several other similar cases in our experience with COVID pneumonia. This is further supported by a case presented by Yoon SH et al. in which the sparing of the juxta pleural region is well observed (4) . Therefore, extending the result of the previous study by Donnelly (5) to the COVID pneumonia should be made with caution.

We agree with the authors that the temporal evolution of CT findings could be useful in differentiating COVID-19 infection and pulmonary contusion, however, given the overlapping features of lung contusion and COVID-19 pneumonitis in chest CT scan, we want to stress the fact that attributing the initial chest CT scan findings to COVID-19 pneumonitis is not possible in many cases. Less than perfect sensitivity of the currently available gold diagnostic standard (RT-PCR) has led many centers to shift the diagnosis to clinical findings plus CT scan in many centers, especially when RT-PCR is scarce and unavailable. It should, however, be emphasized that the predictive value of the so-called "typical" CT findings is yet unknown and that the test performance depends very much on the pretest probability. It is thus expected that in asymptomatic patients the pretest probability is reduced. This is one reason why CT scan is not a proper screening method. Although to our knowledge there is no current literature on the performance of CT scan as a diagnostic test when there is a coexisting/underlying lung condition, we suspect an even lower diagnostic performance in such cases. This conclusion is probably specifically true in case of coexisting lung contusion and trauma.

We thus caution the possibility of over-diagnosis of COVID-19 based on chest CT scan alone in the case of asymptomatic patients with multiple trauma and possible lung contusion. We want to strongly urge the trauma surgeon and fellow emergency radiologists to take lab data and exposure history into consideration before labeling CT scans in trauma patients as typical for COVID-19 during the pandemic. 

COVID-19 or Pulmonary Contusion? A Diagnostic Dilemma. Academic Radiology

Lung contusion: a clinico-pathological entity with unpredictable clinical course

Traumatic pulmonary pseudocyst. International journal of critical illness and injury science

Chest radiographic and CT findings of the 2019 novel coronavirus disease (COVID-19): analysis of nine patients treated in Korea. Korean journal of radiology

Subpleural sparing: a CT finding of lung contusion in children