Objective: Our objective was to determine and report the CT findings in patients with diffuse pulmonary lymphangiomatosis (DPL).

Materials and methods: We retrospectively reviewed the CT findings in eight patients with pathologically proven DPL. The patients ranged in age from 3 to 35 years (mean 15 years) and included four male and four female patients. The CT scans were analyzed for type of pulmonary infiltrative process and its distribution, presence or absence of pleural fluid or thickening, and presence or absence of thoracic lymphadenopathy.

Results: The main abnormality seen on conventional and high resolution CT in all patients was smooth thickening of the interlobular septa and bronchovascular bundles. Seven of eight patients had patchy bilateral areas of ground-glass attenuation. All eight patients had diffuse increased attenuation of the mediastinal fat, approximating that of water, and mild bilateral perihilar infiltration. Seven of the eight had bilateral pleural effusions or smooth thickening of the pleura (or both), and two had regions of calcified pleural thickening.

Conclusion: The constellation of CT features of DPL is distinctive and includes diffuse, smooth thickening of interlobular septa and bronchovascular bundles with extensive infiltration of the mediastinal fat and associated perihilar infiltration. Since the CT findings described are suggestive but not pathognomonic, definitive diagnosis requires lung biopsy.