Fact-sheet: Usual interstitial pneumonia
Updated on 09/05/2019 at 9:26 AM
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Definition
= Idiopathic interstitial pneumonia
= UIP - Usual interstitial pneumonia
The most common form of idiopathic chronic interstitial pneumonia.
UIP may also be secondary (to scleroderma, for example).
Clinical features
Progressive dyspnea, dry cough, basal crackles.
Digital clubbing.
Deterioration of general condition.
Restrictive pattern on pulmonary function tests.
Laboratory findings
Bronchoalveolar lavage: mild lymphocytosis that decreases over the course of the disease, giving way to neutrophilia.
BAL is not routinely recommended when the CT pattern is typical.
Radiography
Bilateral reticulonodular opacities predominating in the lung bases (apicobasal gradient).
CT
2018 CT criteria (American Thoracic Society) for the usual interstitial pneumonia pattern (UIP) --> 4 categories
UIP PATTERN:
- Subpleural and basal predominance, often heterogeneous
- Honeycombing (must be present) with or without traction bronchiectasis.
PROBABLE UIP PATTERN:
- Subpleural and basal predominance, often heterogeneous distribution
- Reticulation with peripheral traction bronchiectasis or bronchiolectasis
- Ground-glass opacity possible but not predominant
INDETERMINATE PATTERN FOR UIP (but not suggestive of another diagnosis):
- Subpleural and basal predominance
- Reticulation with possible ground-glass opacities or distortion (= early UIP pattern)
- No CT criteria suggesting another etiology
ALTERNATIVE DIAGNOSIS = criteria suggesting another diagnosis among the following:
- Cysts
- Mosaic attenuation
- Predominant ground-glass opacity
- Profuse micronodules
- Centrilobular nodules
- Nodules
- Consolidations
- Peribronchovascular, perilymphatic distribution, predominating in the mid lung zones or apices
- Pleural plaques (Asbestos related disease?)
- Dilated Esophagus (connective tissue disease?)
- Distal clavicular erosions (rheumatoid arthritis?)
- Extensive lymphadenopathy
- Pleural thickening or pleural effusion (connective tissue disease/drug-induced cause?)
The diagnosis of idiopathic pulmonary fibrosis requires:
- absence of an identifiable cause of pulmonary fibrosis
- the presence of a UIP pattern on CT
- specific combinations between CT criteria and histopathological criteria (four diagnostic categories are also found on histopathology: UIP, probable UIP, indeterminate pattern for UIP, or alternative diagnosis).
Histologic-CT combinations allowing the diagnosis of Idiopathic Pulmonary Fibrosis:
- CT pattern of UIP + histologic pattern of UIP or histologic pattern of probable UIP or histologic pattern indeterminate for UIP
- CT pattern of probable UIP + histologic pattern of UIP or histologic pattern of probable UIP
- CT pattern indeterminate for UIP + histologic pattern of UIP
Histologic-CT combinations allowing the diagnosis of probable Idiopathic Pulmonary Fibrosis:
- Alternative CT diagnosis + histologic pattern of UIP
- CT pattern indeterminate for UIP + histologic pattern of probable UIP
- CT pattern of probable UIP + indeterminate histologic pattern
Histologic-CT combinations ruling out the diagnosis of Idiopathic Pulmonary Fibrosis:
- Alternative CT diagnosis + histologic pattern of probable UIP or histologic pattern indeterminate for UIP or alternative histologic diagnosis
- CT pattern indeterminate for UIP + alternative histologic diagnosis
- CT pattern of probable UIP + alternative histologic diagnosis
- CT pattern of UIP + alternative histologic diagnosis
reference: Diagnosis of Idiopathic Pulmonary Fibrosis An official ATS/ERS/JRS/ALAT Clinical Practice Guideline, G. Raghu and al, June 2018
Classification
In summary:
Patient suspected of Idiopathic Pulmonary Fibrosis: search for a secondary cause (drug-induced, systemic, toxic exposure, iatrogenic...).
In the absence of a secondary cause:
- If the CT shows a typical UIP pattern (see CT above), after discussion at a multidisciplinary team meeting, the diagnosis of Idiopathic Pulmonary Fibrosis can be made without lung biopsy.
- If the CT shows one of the three other categories (probable UIP pattern, indeterminate pattern for UIP, or alternative diagnosis), bronchoalveolar lavage and biopsy are discussed at the multidisciplinary team meeting but will probably be recommended.
Differential diagnosis
Causes of diffuse infiltrative lung disease predominating in the lower zones of the lungs:
- Lymphangitic carcinomatosis
- Scleroderma
- Asbestos related disease
- Lymphangioleiomyomatosis
- Chronic aspiration pneumonia with fibrosis