key: cord-1052741-ovzb1d6x authors: Kosem, Esra Gurdal; Balik, Recep title: Pseudocavitation Sign at Chest CT Scan due to COVID-19 Pneumonia: A report of Five Cases and Literature Review date: 2021-08-16 journal: Radiol Case Rep DOI: 10.1016/j.radcr.2021.08.034 sha: ab1d3377ef0d554115ce180c612f9d37c159b36a doc_id: 1052741 cord_uid: ovzb1d6x COVID-19 pneumonia computed tomography (CT) imaging features have been described in detail in many studies. The pseudocavitation sign has not been described in the previous COVID-19 studies. We present chest CT scans of five RT-PCR positive patients with COVID-19 pneumonia who has bare areas among pulmonary infiltrates. All five also had previous scans with similarly sized low attenuated areas in the same location prior to the addition of pulmonary infiltrates. The pre-existing cystic changes had become remarkable due to the contrast around them after the pulmonary infiltrates added. Therefore, they should be termed as “pseodocavity" according to Fleischner Society glossary. Small air-containing spaces between pulmonary infiltrates have been termed in previous COVID-19 studies as a new sign called "round cystic changes/air bubble sign/vacuolar sign". We would like to draw attention that the vacuolar sign and the synonyms may be the pseudocavity sign that is due to pre-existing changes rather than a new defined sign. . Chest CT had an important role in describing and differentiating COVID-19 pneumonia and appears to be a sensitive imaging modality. The findings in the scans were similar to the other viral pneumonias [3, 4] . Chest CT findings of COVID-19 pneumonia were reported as GGO (ground glass opacification), mixed GGO with interlobular septation, consolidation or linear densities, reverse halo sign, bronchial wall thickening, arcade-like pattern, bronchiectasis, CT halo sign [5, 6, 7, 8] . The vacuolar sign and the synonyms (cavity, cystic changes, air bubble sign) were reported as COVID-19 pneumonia CT scan feature of unknown pathophysiology (Table 1) [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] . We present five cases of RT-PCR positive patients with COVID-19 pneumonia who had bare areas (pseudocavities) among pulmonary infiltrates in their CT scans. They had previous scans with emphysematous/cystic changes or low attenuated areas in the same location. All scans were performed in a single center on two CT devices in a single center. [(Aquilion Lightning, Canon Medical Systems, 16-row 32 slice helical CT; 5mm slice thickness, 120kVp, 100mAs, noncontrast CT) and (GE Optima CT660, 128-slice CT scanner;1.3mm slice thickness, 120kVp, 100mAs, non-contrast CT)]. The first patient was a seventy-two-year-old male with a history of recent travel to Spain ten days ago in March 2020. He had been complaining of fever and cough for a week. In the initial CT scan, 4 there were peripherally distributed insignificant GGO's in the lower lobes. There were also peripherally distributed thin-walled cystic changes that are not related with the pneumonia in the upper lobes (Fig 1a, c) . The follow-up scan on the seventeenth day of the onset of the illness showed involvement of all five lobes with consolidation in the upper lobes. The pre-existing cystic changes had become remarkable due to the contrast around them. The pseudocavities were seen as small cystic lakes among the areas of consolidation (Fig. 1b, d) . He was discharged after a seventeen days hospitalization. The second patient was a sixty-five-year-old male complaining of fever for a day. He had the initial CT scan on the first day of the disease and the follow-up scans on the fourth and ninth days. The initial scan showed a few insignificant GGO's in the right lower lobe (Fig 2a, d) . On the first follow-up scan multifocal GGO's located peripherally were noted. On the second follow-up scan on the ninth day GGO's were enlarged and merged forming diffuse GGO's located peripherally. Among the GGO's small low-attenuated areas (pseudocavity) were recorded (Fig 2b, e) . When the initial scan was reevaluated, it is was noted that there were already small thin-walled low-attenuated insignificant areas in the same location (Fig 2a, d) . He was discharged after an eleven-day hospitalization. A third CT scan was performed when the patient was admitted to the hospital again due to cough five months after discharge. In the scan, GGOs were observed to have almost completely regressed and pseudocavitation areas were seen as barely distinguishable air spaces, similar to imaging before Covid involvement (Fig 2c, f ). The third patient was a seventy-two-year-old male who visited the emergency service (ER) complaining of fever and coughing in April 2020. He had gastric cancer and had undergone gastric 5 surgery fifteen days ago. The thoracoabdominal CT scan before the surgery showed emphysematous changes in lung parenchyma, especially located peripherally, in the subpleural areas without the features of pulmonary infiltrates (Fig 3a) . The chest scan on the day of admission had pneumonia manifestations. There was bilateral lung involvement including marked cystic areas (pseudocavitations) among the consolidation (Fig 3b) . Bilateral pleural effusion was also recorded. He required admission to intensive care unit (ICU) on the fourth day of hospitalization. He had also accompanying gastrointestinal problems (abscess) and died after an eight-day hospitalization in the ICU. The fourth patient was a sixty-three-year-old male who visited the ER complaining of coughing for fourteen days in March 2020. There were patchy GGO's on all five lobes in the initial CT scan (Fig 4a) . He had the second chest scan eight days later when he complained of shortness of breath. The follow-up scan showed consolidation within enlarged and merged GGO's. On the right middle lobe there was a spare area (pseudocavitation) within the GGO's (Fig 4b) . When the initial scan was reexamined, it was noted that there was already a small area more lucent than peripheric lung tissue (Fig 4a) . He was transferred to another hospital's ICU after ten-day hospitalization and died thirteen days later in the ICU. Forty-three-year-old female patient with a history of asthma and rheumatoid arthritis visited ER complaining of a cough. The initial CT scan showing thin-walled cyst within normal lung parenchyma on the right upper lobe, which did not have the pulmonary infiltrates (Fig 5a) , and she was not hospitalized. She applied to the ER again with the complaint of a cough that would not go away, but had gotten worse. A follow-up chest scan (Fig 5b) taken twenty days later showed consolidation within GGO's in all lobes. The cyst in the initial scan on the right upper lobe was seen as a pseudocyst 6 among the consolidation in the control scan. She was transferred to another hospital's ICU after seven-day hospitalization. She died on the thirteenth day of hospitalization in ICU. The CT findings of COVID-19 pneumonia were reported in detail in the previous studies [5, 6, 8] . CT manifestations of COVID-19 resemble those seen in viral pneumonias [3, 4] . In previous studies the low attenuated spaces among consolidated areas were reported in different names as cavity [9] , round cystic change [7] , air bubble sign [10] or vacuolar/intralesional vacuole sign [11, 12] in COVID-19 pneumonia (Table 1) [7, 9, [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] . The pathophysiology of these cystic changes in areas of infiltrates remains unclear. Shi et al. [7] described round cystic changes in 10% of patients and suggested that they might be associated with the process of resorption of consolidation which might be explained by the infection causing damage to the alveolar walls and leading to pneumatoceles. Ye et al. [10] referred these small air containing spaces as air bubble sign and suggest that they might be the pathological dilation of a physiological space or a cross section of the bronchiolectasis, or associated with the process of consolidation resorption. Zhou et al. [11] was the first authors referring to as the vacuolar sign. They described as a vacuole-like transparent shadow of < 5 mm in length observed in the lesion. They reported 45.2% of the patients' scans show vacuole sign, and observed vacuolar sign often in the advanced phase of COVID-19 pneumonia (8-14 days after symptom onset), associated with interstitial involvement and accompanied by repair changes. In their later study the same group suggested that the vacuolar sign might be due to the inhomogeneous involvement and incomplete filling of alveoli and it was characteristic especially during the advanced stage [20] . Zhang et al. [12] reported the intralesional vacuole sign in 17.65% of the patients in their study and mentioned that it might be the dilation of alveolar ducts and alveolar sac, indicating the alveolar destruction and onset of fibrosis and also argued that it could be a feature of the progressive stage. Zhu et al. [17] mentioned that young group showed the vacuolar sign 21 %, while elderly group had 15 %. Cinkooglu et al suggested that air-bubbles could not be seen easily on the source images, and that might be the reason for the relatively low rate [18] . Rodrigues et al. [21] mentioned that 30.2% patients presented cystic changes; 11.6% patients had cystic airspaces only in the subpleural region and along the peribronchovascular interstitium, and 18.6% had cystic airspaces admixed with areas of opacity in the lung parenchyma. There was a difference in the frequency of these changes among studies (Table) [7, 9, [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] . Cavities are described as the gas-filled spaces or low-attenuation areas within consolidations that appear as a solution of the drainage of a necrotic part of the lesion [23] . During the course of the disease, cavitation can develop in viral pneumonias (25) . But the small bare areas among pulmonary infiltrates in the presented case series were already in the area before consolidation or GGO occurred. According to Fleischner Society, pseudocavity is a term used to describe small lakes or vacuoles among masses or consolidation areas. Pseudocavity represents spared parenchyma, normal or ectatic bronchi, or focal emphysema rather than cavitation. It was described in patients with some malign disease as well as some benign conditions as infectious pneumonia [12] . The case series we presented had emphysematous or cystic changes in the initial scans. Although these cystic areas remained the same in size and shape, they became more prominent due to the contrast in the surrounding consolidated areas after pulmonary infiltration was added. Pseudocavity was described in other viral pneumonias as influenza A (H5N1) [3, 4, 25] . The initial imaging findings of COVID-19 pneumonia are not organism specific and can overlap with H1N1 influenza, cytomegalovirus pneumonia, and other atypical pneumonias [8] . Studies has shown that the advanced phase signs in scans were also similar to the other pneumonias [6, 24] . Therefore, we suggest that COVID-19 pneumonia is not expected to be organize differently from all known pneumonias. In the previous studies similar cystic changes seen among consolidations were discussed to be a result of resorption of consolidation or alveolar destruction as a feature of the progressive stage. Our data indicate that it is not possible to decide on the pathogenesis of such changes observed in pneumonia, without the knowledge of pre-existing pathological changes in the lungs. The purpose of presenting and terming these changes is to draw attention since the so-called vacuolar sign and the synonyms described in COVID-19, may be due to preexisting emphysematous changes/ focal areas of air trapping due to chronic small airway disease, rather than due to a postulated theory of resolution of opacities/ focal sparing/ due to bronchiolar destruction. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Poster Presentation: 41th Turkish Radiology Congress, 24 October-1 November 2020, Antalya/Turkey. All data available upon request. There are no conflicts to declare. WHO Declares COVID-19 a Pandemic Radiographic and CT Features of Viral Pneumonia Imaging of pulmonary viral pneumonia Radiological Society of North America Expert Consensus Statement on Reporting Chest CT Findings Related to COVID-19. Endorsed by the Society of Thoracic Radiology, the American College of Radiology, and RSNA -Secondary Publication Coronavirus Disease 2019 (COVID-19): A Systematic Review of Imaging Findings in 919 Patients Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study An update on COVID-19 for the radiologist -A British society of Thoracic Imaging statement Chest Imaging Appearance of COVID -19 Infection. RadiolCardiothorac Imaging Chest CT manifestations of new coronavirus disease 2019 (COVID-19): a pictorial review CT Features of Coronavirus Disease 2019 (COVID-19) Pneumonia in 62 Patients in Wuhan, China CT imaging features of 34 patients infected with COVID-19 Clinical characteristics and imaging manifestations of the 2019 novel coronavirus disease (COVID-19): a multi-center study in Wenzhou city Clinical Features and Chest CT Manifestations of Coronavirus Disease CT characteristics of patients infected with 2019 novel coronavirus: association with clinical type COVID-19 pneumonia manifestations at the admission on chest ultrasound, radiographs, and CT: singlecenter study and comprehensive radiologic literature review A Comparative Study of Chest Computed Tomography Features in Young and Older Adults with Corona Virus Disease (COVID-19) CT imaging features of COVID-19 pneumonia: initial experience from Turkey A new imaging sign in COVID-19 pneumonia: vascular changes and their correlation with clinical severity of the disease Imaging features and evolution on CT in 100 COVID-19 pneumonia patients in Wuhan, China Cystic airspaces associated with COVID-19 pneumonia Chest CT Findings after 4 Months from the Onset of COVID-19 Pneumonia: A Case Series Fleischner Society: glossary of terms for thoracic imaging Organizing pneumonia: what is it? A conceptual approach and pictorial review The radiologic manifestations of H5N1 avian influenza The author would like to thank Stephanie Reaume for English grammar and spelling correction of the manuscript.