COVID-19 with cystic features on computed tomography

Abstract Rationale: The cystic features of the novel coronavirus disease 2019 (COVID-19) found on computed tomography (CT) have not yet been reported in the published literature. We report the cystic chest CT findings of 2 patients confirmed to have COVID-19-related pneumonia. Patient concerns: A 38-year-old man and a 35-year-old man diagnosed with severe COVID-19 pneumonia were admitted to the intensive care unit. Diagnoses: Chest CT findings showed multiple cysts in ground-glass opacities (bilaterally) with/without pneumothorax. The cysts had a smooth inner wall. Interventions: The patients continued to be given oxygen by mask and received antitussive, phlegm-dispelling treatment. Outcomes: At follow up, there was a reduction in the number of multiple cystic lesions on CT. To date, 1 patient was discharged from hospital, while the other had been transferred to the rehabilitation department. Lessons: COVID-19 may independently result in pulmonary cyst formation and pneumothorax; the application of a ventilator may be another causative factor.


Introduction
The typical chest computed tomography (CT) findings of the novel coronavirus disease 2019 (COVID-19) appear as multiple patchy, ground-glass opacities that progress to or co-exist with bilateral consolidations in multiple lobes and with peripheral distribution [1][2][3] ; however, the cystic features of COVID-19 on CT have not yet been reported in the literature. Here, we report the chest CT findings of cystic lesions in 2 patients confirmed to have COVID-19 pneumonia. Of note, written informed consent was obtained from both patients to publish this case report.

Case 1
A 38-year-old man diagnosed with severe COVID-19-related pneumonia (6 days) was admitted to the intensive care unit. The primary CT findings showed bilateral, patchy, ground-glass opacities with co-existing consolidations (Fig. 1A). The patient presented with shortness of breath, chest pain, 92% percutaneous oxygen saturation, and 26 breaths/minute; the patient was thus given 5 L/minute of oxygen by mask. However, 26 days later, follow-up CT findings showed multiple cysts in the groundglass opacities (bilaterally) and the development of a ∼20% left pneumothorax. The cysts had a smooth inner wall and the maximum diameter of these cysts was ∼5 cm (Fig. 1B). At this time, real-time fluorescent polymerase chain reaction of the patient's sputum was negative for COVID-19 nucleic acid. The patient continued to be given 4 L/minute of oxygen by mask, as well as an antitussive, phlegm-dispelling treatment. The third CT scan, which was performed 5 days after the second CT scan, showed that the left pneumothorax and 1 small cyst on the left The authors have no conflicts of interest to disclose.
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.  Medicine pulmonary margin had disappeared; the remaining cysts were slightly reduced in size (Fig. 1C). The patient was discharged from the hospital 21 days after the third CT scan.

Case 2
A 35-year-old man diagnosed with severe COVID-19 pneumonia (9 days) was admitted to the intensive care unit. The primary CT findings showed bilateral, patchy, ground-glass opacities and consolidations ( Fig. 2A and B). The patient developed acute respiratory distress syndrome (ARDS) and type I respiratory failure; as such, the patient was given assisted respiration via a noninvasive ventilator (the inspiratory positive airway pressure ranged from 20 to 26cm H 2 O; the expiratory positive airway pressure ranged from 5 to 10cm H 2 O), as well as anti-infective, antivirus treatment. Forty days later, the CT scan findings showed bilateral, patchy consolidations, and multiple cystic lesions (bilaterally) with peripheral distribution (Fig. 2C and D). At present, real-time fluorescent polymerase chain reaction of the patient's sputum was negative for COVID-19 nucleic acid. To treat the patient's paroxysmal cough, which featured a little white mucus, as well as to address the patient's 97% percutaneous oxygen saturation with 19 breaths/minute, the patient's antitussive, phlegm-dispelling treatment was continued. Two days later, the multiple cystic lesions were slightly reduced in size on follow-up CT ( Fig. 2E and F). At the time this paper was submitted for publication, the patient had been transferred to the rehabilitation department.

Discussion
To date, the papers published on COVID-19 have not discussed the presence of cystic lesions in association with this disease. In both of our cases, the pulmonary cystic lesions of COVID-19 were found on CT. The pulmonary cystic lesions and pneumothorax that were found may have been complications associated with mechanical ventilation. [4,5] The incidence of barotrauma in patients with ARDS following ventilation therapy was 6.5%. [6] Most ventilation-associated cysts were small (<1 cm in diameter) and featured a thick wall with no appreciable internal structure, and were found in a subpleural location. [7] However, some of the literature reported that ARDS might independently result in cyst formation. [7,8] The pulmonary cysts were observed in severe acute respiratory syndrome patients who received only short-term, low-pressure, and volume ventilation or received no mechanical ventilation at all. [7] The reasons for this might include the development of ischemic parenchymal damage, lung fibrosis, low lung compliance, and inflammatory exudate in the airway. [7][8][9] The pulmonary cysts and pneumothorax that were observed in both of our cases occurred more than 30 days after symptom onset; both patients were in the intermediate and late stages of ARDS, which is when fibrous processes begin to appear. [10] Case 1 did not receive mechanical ventilation therapy; therefore, we speculate that ischemic parenchymal damage, lung fibrosis, and low lung compliance may have led to the formation of cysts and the development of a pneumothorax. Case 2 received a noninvasive ventilator; thus, the application of the ventilator may have constituted an additional reason for the formation of cysts and the development of a pneumothorax.
Recent histological examinations reported bilateral diffuse alveolar damage with cellular fibromyxoid exudates in COVID-19. [11] Pulmonary cystic lesions may form in response to cellular fibromyxoid exudates, which form a valve in the bronchus. Since these lesions cause emphysema and bullae, phlegm-dispelling treatment options may have been more appropriate and effective for both of our cases.
In conclusion, COVID-19 may independently result in pulmonary cyst formation and the development of a pneumothorax; however, the use of a ventilator to manage the symptoms of this disease may be another reason underlying the formation of these lesions in patients affected by this virus.