[Four cases of pulmonary tuberculosis resembling pulmonary abscess with a so-called niveau-like shadow in a medical school hospital: discussion concerning the formation mechanism of niveau-like shadows].

Four cases of pulmonary tuberculosis resembling pulmonary abscess radiographically were reviewed from their clinical features, chest X-ray and chest CT, and the mechanism of formation of so-called niveau-like shadows was discussed. Only one case showed a newly formed tuberculous cavity with air fluid level on chest X-ray, however, even in this case, the possibility of the infection with tubercle bacilli of an emphysematous bulla of the lung could not be completely excluded as several bulla were found on chest CT. The remaining three cases showed a slightly different mechanism of the formation of niveau-like shadows. Namely, mycobacterium tuberculosis spread into an existed bulla and a tubercle bacilli infected bulla was formed. Regarding the clinical features, no remarkable findings were detected and we could find no differences with common tuberculosis. Based on these experiences, the presence of pulmonary tuberculosis resembling the shadow of pulmonary abscess should be emphasized.