CT Features Suggesting Idiopathic Pulmonary Fibrosis in Patients with UIP Pattern

Key Diagnostic HRCT Features of UIP/IPF

The American Thoracic Society recommends that the definitive UIP pattern on HRCT that suggests IPF includes subpleural and basal predominant distribution with honeycombing, with or without peripheral traction bronchiectasis or bronchiolectasis 1, 2
The American College of Chest Physicians suggests that the distribution pattern of subpleural and basal predominant distribution, often heterogeneous, is a key feature of UIP/IPF 1, 2
The European Respiratory Society notes that essential features of honeycombing with or without traction bronchiectasis are the hallmark radiological findings of UIP/IPF 1, 3
The presence of irregular thickening of interlobular septa is a reticular abnormality that supports the diagnosis of UIP/IPF 2, 3

The American Thoracic Society states that a probable UIP pattern may have the same subpleural and basal predominant pattern as definite UIP, with key findings of reticular pattern with peripheral traction bronchiectasis or bronchiolectasis 1, 2
The American College of Chest Physicians recommends that associated findings, such as mild ground-glass opacities, may be present in probable UIP patterns 2, 3
The European Respiratory Society suggests that a provisional high confidence (70-89%) for IPF diagnosis can be made when clinical context is appropriate for probable UIP patterns 2

The American Thoracic Society notes that upper or mid-lung predominance is inconsistent with IPF, which characteristically affects the bases 1, 2
The American College of Chest Physicians states that peribronchovascular predominance with subpleural sparing suggests NSIP rather than IPF 2, 3
The European Respiratory Society recommends that extensive ground-glass abnormalities, when extent is greater than reticular abnormality, are inconsistent with UIP/IPF 1, 3

The American Thoracic Society suggests that a definite UIP pattern on HRCT is associated with high confidence (<90%) for IPF diagnosis 2
The American College of Chest Physicians recommends that a probable UIP pattern is associated with provisional high confidence (70-89%) for IPF diagnosis 2

The American Thoracic Society recommends that a multidisciplinary discussion involving pulmonologists, radiologists, and pathologists is essential when HRCT features are not definitive for UIP 2, 3
The American College of Chest Physicians states that surgical lung biopsy may be necessary when HRCT pattern is indeterminate for UIP or suggests an alternative diagnosis 2, 3
The European Respiratory Society suggests that the diagnosis of IPF requires exclusion of known causes of interstitial lung disease, such as drug exposure, inhalational exposure, and connective tissue disease 1, 4

The American Thoracic Society recommends that probable UIP demonstrates a reticular pattern with peripheral traction bronchiectasis or bronchiolectasis in a subpleural and basal predominant distribution 5
Honeycombing is absent in probable UIP pattern, which is a critical distinction from definitive UIP pattern, as stated by the American Thoracic Society 5, 6
The American Thoracic Society describes indeterminate UIP as showing CT features and/or distribution of lung fibrosis that do not meet UIP or probable UIP criteria and do not explicitly suggest an alternative diagnosis 5

The American Thoracic Society suggests that age >60 years with unexplained bilateral pulmonary fibrosis increases confidence in IPF diagnosis even with indeterminate imaging 6, 7
Smoking history and environmental/occupational exposures must be systematically evaluated to exclude secondary causes, according to the American Thoracic Society 6
Bibasilar inspiratory crackles on examination support the diagnosis, as stated by the American Thoracic Society 6, 7

The American Thoracic Society recommends that surgical lung biopsy is suggested to confirm diagnosis for probable UIP patterns 7
Multidisciplinary discussion involving pulmonologists, radiologists, and pathologists is essential before proceeding to biopsy, as recommended by the American Thoracic Society 7
IPF diagnosis can be made without biopsy if multidisciplinary discussion produces confident diagnosis with supportive features, such as moderate-to-severe traction bronchiectasis in ≥4 lobes, age >50 (men) or >60 (women), or extensive reticulation (>30%) with age >70, according to the American Thoracic Society 8

The American Thoracic Society requires thin-section CT images (<1.5 mm) with high-spatial-frequency algorithm for accurate pattern classification 5
Both inspiratory and expiratory acquisitions help detect air trapping and assess for alternative diagnoses, as stated by the American Thoracic Society 5