Role of CT scan thorax in nCovid19—a case-based review

Abstract

Most of the morbidity and mortality in nCovid19 is due to pneumonia which can be reduced by early diagnosis and treatment. Chest CT scan plays an important role in the early diagnosis and management of respiratory complications due to nCovid19. Clinicians should be aware about the indications for the CT scan of the thorax, timing of investigation, and limitations of CT. Chest CT scan is indicated in patients with moderate to severe respiratory symptoms and pretest probability of nCovid19 infection, when RT-PCR test results are negative, and in patients for whom an RT-PCR test is not performed or not readily available. When a rapid antigen test is negative and an RT-PCR test report takes time, CT can be used in seriously ill patients to decide whether it is COVID or not. For patients who are dependent on oxygen even after 2 weeks, CT may help to show the extent of lung involvement and predict long-term prognosis. CT may be done to exclude nCovid19 pneumonia. For patients with high risk for nCovid19 who require an immediate diagnosis to rule out lung involvement, CT can be done. A normal CT excludes nCovid19 pneumonia. CT scan is required in confirmed cases of nCovid19 pneumonia when complications are suspected clinically. These include pulmonary thromboembolism, pneumothorax, mediastinal/surgical emphysema, bacterial pneumonia, and unexplained deterioration with new shadows in chest X-ray. CT pulmonary angiogram is indicated when pulmonary embolism is suspected, and in other cases, plain CT should be done. In pre-operative cases where emergency surgery is required, nCovid19 disease is suspected clinically, and RT-PCR report awaited or not available, CT thorax can be done. CT scan is useful for early diagnosis of lung involvement, detection complications, triaging of cases, risk stratification, and preoperative evaluation in select cases. CT scan should be done only when there is a definite indication so to reduce radiation hazards and to reduce health care expenditure. Normal CT excludes nCovid19 lung involvement, but the patient may have upper respiratory involvement which may progress later to involve lungs.