HRCT in Miliary Lung Disease

Purpose: To analyze high resolution CT (HRCT) features of a miliary pattern in different diseases. Material and Methods: Eight HRCT studies with a miliary lung pattern were retrospectively reviewed with the diagnoses tuberculosis (n=3), Candida albicans (n=1), sarcoidosis (n=3), and metastatic adenocarcinoma (n=1). Results: In all cases, HRCT showed diffusely disseminated nodules up to 3 mm. In 2 cases of tuberculosis and 1 of sarcoidosis, the lesions predominated in the upper middle lung zones. In the case of metastatic adenocarcinoma the nodules were more sparse in the lung periphery while in 1 case of sarcoidosis, HRCT revealed a predominance of the lesions in the outer third of the lungs. Cyst-like lesions of 1-2 mm were observed in 2 3 cases of tuberculosis and in metastatic adenocarcinoma. Notably thickened interlobular septa and interlobar fissures were each seen in 2 3 cases of sarcoidosis. In general, a random relationship of miliary nodules to secondary lobular structures and bronchovascular bundles was observed, despite the co-existence of centrilobular, subpleural and paraseptal nodules. Conclusion: HRCT features that potentially contribute in making a differential diagnosis are: a) A peripheral distribution of nodules, an increased number of thickened interlobular septae, and a notable thickening of interlobar fissures, all of which are indicative of sarcoidosis; and b) Multiple cyst-like lesions which should direct attention to tuberculous or metastatic origin. The predominance of miliary nodules in relation to cephalocaudal axis, their margin and size are not helpful features to the differential diagnosis of diseases presenting a miliary pattern.