According to the lower prevalence of COVID-19 among children, compared to that reported for adults, there have been no sufficient data on the clinical and imaging features of COVID-19 and its typical and atypical manifestations in children.
Based on the current criteria, laboratory data have become a standard tool for the diagnosis of COVID-19 infection. However, laboratory tests are time-consuming and a chest CT scan can be diagnostically helpful; however, the chest CT manifestations of COVID-19 pneumonia are diverse in pediatric patients [7]. Milder cases showed normal chest CT scans [8,9,10]. Pediatric patients showed milder symptoms and normal CT scans in comparison to those reported for adults (50% and 8.5%, respectively) [11] that may lead to missed diagnosis.
In the present cases, the older sister showed more severe symptoms. She had also rare COVID-19 symptoms, such as diarrhea. She was hypoxic with respiratory distress and required to be admitted to ICU. In addition, she had lymphopenia, and CRP was strongly positive .Her imaging pattern was predominantly compatible with focal segmental/lobar consolidation, which is considered an atypical feature of COVID-19 pneumonia according to the RSNA guidelines. The older case was treated according to Iranian expert’s consensus protocols [12].
The younger sister later became symptomatic with milder clinical symptoms. However, her imaging patterns of lung involvement were mild generalized patchy GGO and relatively mild and symmetrical distribution scattered in both lungs, with mild reticular density considered an indeterminate feature of COVID-19 according to the RSNA guidelines. However, lower lobe predominance in both cases was compatible with the lung involvement pattern of adult COVID-19. Furthermore, the absence of adenopathy, nodule cavitation, and pleural effusion was also in line with that reported for adult COVID-19.
According to the RSNA, American College of Radiology, and Society of Thoracic Radiology, there are some guidelines for CT interoperation in adults [5]. The guidelines provide radiologists with guidance for the diagnosis of adult COVID-19; however, there are no sufficient consensus criteria for pediatric patients. There are several reports on different imaging points between pediatric patients and adults.
Soltani et al. reported that the RSNA criteria cannot be generalized to pediatric patients. They also reported that only 20.7% of confirmed cases with RT-PCR showed a typical appearance of a chest CT scan. Moreover, 79.7% of these cases showed another finding considered inconsistent with CT manifestation of COVID-19. Soltani et al. emphasized that in symptomatic pediatric patients with recent close contact with COVID-19 patients, even in the presence of inconsistent appearance and atypical CT feature, the diagnosis of COVID-19 is highly probable [13].
Wei Xia et al. reported that there are different patterns of lung involvement in children. They emphasized that consolidation with a surrounding halo in pediatric patients was more common than adults, mostly due to underlying co-infection [14]. According to the overlap of COVID-19 pneumonia with other viral pathogens in a chest CT scan, they concluded that the diagnosis of COVID-19 pneumonia only by CT imaging is not enough, especially in patients with co-infection. Therefore, a chest CT scan combined with pathogen detection is a reasonable tool for diagnosis. According to a report presented by Yani Duan et al., there were more atypical CT scan manifestations in the pediatric groups, including rare interlobular septal thickening and localized GGO with a lower density of GGO [15].
Regarding the report of severe acute respiratory syndrome coronavirus 2 infection among children in the New England Journal of Medicine, out of 1391 children evaluated for the diagnosis of COVID-19, 171 cases (12.3%) were confirmed with COVID-19 infection. The most common abnormality on the chest CT scan was GGO among the cases. Local patchy shadowing, bilateral patchy shadowing, and interstitial abnormality were present in 18.7%, 12.3%, and 1.2% of the cases, respectively [16]. Therefore, this presentation is less common in children than that reported for adults.
In a study carried out by Haiyan Qiu et al. on 36 children (mean age: 8.3 years), the infection in 89% of the patients was transmitted through contact with family members; however; 33% of the subjects had a history of exposure to epidemic regions, and 47% of the cases showed mild clinical symptoms. Furthermore, less than one-third of the patients were asymptomatic, and the GGO pattern was observed in 53% of patients’ chest CT scans [17]. In another study conducted by Babyn PS et al., it was emphasized that the prevalence of pneumonia in children with COVID-19 is higher than that reported for H1N1 influenza (53% and 11%, respectively) [18].
With respect to the RSNA definition for CT scan reporting, pediatric patients more frequently demonstrate atypical and indeterminate patterns in chest CT scans. Therefore, it seems that the criteria for the application of typical and atypical in the CT scan reports of children need to be redefined.
In pediatric patients with COVID-19, a CT scan should be performed with more caution. According to the risk of radiation and high atypical manifestations of CT scans in children and risk of disease spread in hospitals by transferring the patients, CT scans should be considered for highly suspected cases with negative RT-PCR results. In addition, a CT scan should be performed according to the low-dose protocol, and CT follow-up should be reduced for such cases.
Conclusion
The COVID-19 infection in children is less frequently common; however, mild symptoms and atypical imaging findings are possible among children. Atypical clinical symptoms and imaging features are more common among children than adults; therefore, it is required to carry out further studies with more cases for the identification of typical and atypical imaging patterns of COVID-19 pneumonia in the pediatric population. A CT scan, especially according to low-dose protocols, should be considered for highly suspected cases with negative RT-PCR results.