[A case of active pulmonary tuberculosis in the right lower lung field detected by CT]

Many studies have indicated the pitfalls in detecting abnormalities on chest radiography, although radiography of the chest has been used for the screening of peripheral lung cancer. Recently, mass screening with a spiral computed tomography scanner has been performed for the detection of small peripheral lung cancers, and it has been clarified that spiral CT was superior to chest radiography in the screening and detection of peripheral lung cancer. However, there have been only a few reports on pulmonary tuberculosis that was detected by chest CT. We report a case of active pulmonary tuberculosis detected by chest CT, and invisible on plain chest radiography. 39 year old female consulted our hospital, because chest radiography at mass screening for lung cancer showed an abnormal shadow in the left upper lung field. Chest CT revealed a high density nodule with calcification compatible with old tuberculosis. However, there was another 20 mm x 10 mm sized nodule in right S9b that was invisible on plain chest radiography. The nodule had a clear margin with satellite lesion that characterize active pulmonary tuberculosis. Bronchial lavage was performed by bronchofiberscopy, and Mycobacterium tuberculosis was isolated from lavage fluid. The nodular shadow disappeared after the treatment with isoniazid and rifampicin for 9 months.