Hypothesis on the evolution of cavitary lesions in nontuberculous mycobacterial pulmonary infection: thin-section CT and histopathologic correlation.

OBJECTIVE: The objectives of our study were to evaluate the thin-section CT findings of the cavitary form of nontuberculous mycobacterial pulmonary infection and correlate these imaging findings with the histopathologic findings concerning the development of bronchiectasis and of centrilobular nodules and cavitary lesions.

MATERIALS AND METHODS: We retrospectively reviewed thin-section CT scans (2.5-mm collimation, both axial and coronal reformation images) of 24 cases (male-female ratio, 13:11; mean age, 61 years; age range, 43-82 years) of the cavitary form of culture-proven Mycobacterium avium-intracellulare complex pulmonary infection including two cases with lobectomy specimens. Any changes in CT findings detected on the follow-up CT scans that were available for seven patients (follow-up interval, 6-24 months; mean, 12 months) were also assessed.

RESULTS: Thin-section CT findings were bronchiectasis (24/24 patients, 100%), a patent bronchus running into a cavitary lesion (the "feeding bronchus" appearance) (18/24, 75%), nodules less than 10 mm (17/24, 71%), centrilobular nodules (17/24, 71%), nodules of 10-30 mm (13/24, 54%), peribronchial nodules (8/24, 33%), lobular consolidation (6/24, 25%), bronchial wall thickening (4/24, 17%), and consolidation (2/24, 8%). Two lobectomy specimens showed large cavitary consolidations with the feeding bronchus appearance on pathologic specimens. In two patients, small peribronchial nodules had changed into cavitary nodules with the feeding bronchus appearance on follow-up CT, which represented inflamed focal cystic bronchiectasis.

CONCLUSION: In the cavitary form of M. avium-intracellulare complex pulmonary infection, the feeding bronchus appearance is another very frequent thin-section CT finding. This appearance may suggest that peribronchial nodules of M. avium-intracellulare complex infection evolve into inflamed focal cystic bronchiectasis manifesting as cavitary lesions.