CT-pathology correlation of pulmonary tuberculosis

Pulmonary tuberculosis is a chronic granulomatous disease characterized radiologically by nodules, air-space consolidation, propensity for cavitation, and calcification, and pathologically by caseating granulomas or pneumonia, and a great propensity for fibrosis and dystrophic calcification. Primary tuberculosis typically appears as air-space consolidation with hilar or mediastinal lymphadenitis. Postprimary tuberculosis appears most commonly as nodular and linear opacities at the lung apex. CT findings of early bronchogenic spread of postprimary tuberculosis are centrilobular 2- to 4-mm nodules or branching linear structure, 5- to 8-mm poorly defined nodules, lobular consolidation, cavities, and thickening of interlobular septa. Centrilobular nodules or branching linear lesions and poorly defined nodules on CT scan correspond to caseation materials filling the bronchioles, and centrilobular air-space consolidation with caseation necrosis. Poorly defined nodule or lobular consolidation usually consists of central caseation necrosis and peripheral nonspecific inflammation. Cavitation usually occurs at the centrilobular area and may progress to a larger coalescent cavity. With antituberculous therapy, resolution typically occurs from the peripheral portion of the poorly defined nodule or lobular consolidation and results in varying degrees of fibrous bands, bronchovascular distortion, emphysema, and bronchiectasis. Miliary tuberculosis appears as well-defined randomly distributed nodules on CT scan that correspond with nodules consisting of central caseation necrosis and peripheral epitheloid and fibrous tissue. Analysis of CT images on the basis of pathologic correlation is helpful in understanding the morphology of pulmonary tuberculosis.