Tuberculosis can also have shadows when it is well, but not necessarily shadows. Tuberculosis is an infectious disease of the respiratory system caused by infection with Mycobacterium tuberculosis. The underlying cause is the infection of lung tissue by Mycobacterium tuberculosis, which causes chronic damage to lung tissue. It may appear on chest radiographs as dotted, flaky, patchy or cloud-like shadows. For lesions that are small in extent and occur in areas with relatively unobstructed bronchial drainage, shadows do not develop when they are treated with effective anti-tuberculosis therapy and are basically completely absorbed in 6-9 months without leaving any traces in the lungs. However, in the case of untreated tuberculosis, the extent of tuberculosis lesions is larger, the site of occurrence is not well drained, and drug-resistant tuberculosis, in the process of chronic damage and repair, fibrous lesions are not completely absorbed and shadows are left behind.