SMALL AIRWAYS DISEASE
THERESA C. MCLOUD

Diseases of the Small Airways
HRCT is the best imaging modality for the evaluation of diseases of the bronchioles. Although normal bronchioles cannot be recognized radiologically, the various forms of bronchiolitis may lead to characteristic HRCT findings. Small airways diseases are manifested by direct and indirect signs on HRCT scans. These signs correlate with narrowing and obliteration of the bronchiolar lumen, dilation of the lumen, and filling of the lumen with secretions and mucus plugging. Often bronchiolar diseases are associated with more central bronchiectasis. The direct signs include small centrilobular nodules V or Y shaped branching linear opacities (Figure 1). The indirect signs include mosaic perfusion and expiratory air trapping (Figure 2).