Clinical analysis of recent lower lung field tuberculosis.

Because the incidence of lower lung field tuberculosis has recently increased in our affiliated hospitals, we carried out an analysis of its clinical characteristics during the past 10 years. We experienced 15 patients (7.5%) with lower lung field tuberculosis among 201 patients treated between April 1992 and March 1997, and 27 patients (11.1%) with the same condition among 243 patients treated between April 1997 and March 2002. The changes in clinical characteristics shown in the later period were as follows: (1) an increase in the percentage of elderly patients, (2) an increase in the incidence in patients who had received corticosteroid drugs for underlying disease, (3) atypical radiographic findings, such as homogeneous shadows resembling bacterial pneumonia, (4) an increase in microbiologically smear-positive patients, because more bronchoscopic examinations were performed, and (5) a high mortality rate (21.7%) with the increase being due to complications. Because there is a significant problem with nosocomial infections, patients with homogeneous shadows resembling bacterial pneumonia on admission should be examined for acid-fast bacilli containing Mycobacterium tuberculosis. We consider this problem to be not so difficult considering the progress in diagnostic methods for M. tuberculosis.