Table 1.

Classification of lung parenchymal complications in patients with idiopathic pulmonary fibrosis (IPF) and HRCT features.

Acute/Chronic	Complication		HRCT Features
Acute	Infections	Mycobacterium species	Peripheral mass-like lesion/subpleural nodules/segmental or lobar coalescent consolidation with or without necrotising cavitation.
		Pneumocystis jirovecii	Ground glass opacity/no change from the baseline in a clinic context of infection.
		Aspergillus	Fungal fronds in a pre-existing cavity in early stages. Subsequent coalescence of the cavity (air crescent sign).
	Acute exacerbation IPF		New bilateral ground glass opacities and/or consolidation on a background of reticular or honeycombing pattern.
	Right heart failure		Profuse septal thickening, ground glass opacities, pleural effusion on a background of reticular or honeycombing pattern.
Chronic	Lung cancer		Ill-defined rounded lesion, mimicking air space consolidation/nodular lesion developing within peripheral and basal honeycombing areas. Ground glass opacity in fibrosis area (mucinous bronchioloalveolar carcinoma).