In Morning Report on May 24th, we discussed a case of interstitial lung disease and talked about specific details on idiopathic pulmonary fibrosis. See a summary of the key points below:
1. Approach to Interstitial Lung Disease (ILD)
The following diagram outlines an approach to interstitial lung disease:
2. Pearls on Specific Causes of ILD
Exposure-related histories are important when assessing patients with suspected ILD. Hypersensitivity pneumonitis (HP) a non IgE mediated inflammation of the lung parenchyma (acute, subacute, chronic forms). It is caused by sensitization to inhaled agents, usually organic dust. Depending on the antigen, there are other forms of HP such as Farmer’s lung (Thermophilic actinomycetes), Bird Breeder’s or Bird Fancier’s Lung (due to air-borne avian antigen), among others.
Pneumoconioses are related to inhalation of inorganic dusts (0.5 to 5 micro-meters in size). This includes asbestos exposures, silicosis (ask about work including sand-blasting, mining, stone cutting, quarry and highway work), and coal exposures.
Drugs that can cause ILD include:
- Antineoplastic agents such as bleomycin, mitomycin, cyclophosphamide, methotrexate
- Antibiotics: nitrofurantin, penicillin, sulfonamide
- Cardiovascular drugs: amiodarone, tocainide
- Gold salts
- Recreational drugs such as heroin
- Biologics such as rituximab, infliximab, among others
3. Investigations for ILD
The fibrotic ILD Canadian Thoracic Society position statement (referenced below) has key points that are summarized here:
– All patients being evaluated should have high resolution CT chest (HRCT)
– Expiratory and prone high-resolution CT can be valuable
– Continuous images with 0.5-1.25 mm slice thickness is required for evaluation of fibrotic ILD
– Chest HRCT should be interpreted in the context of a multidisciplinary discussion if there diagnostic uncertainty
– All patients fibrotic ILD should get ANA, RF, antiCCP, and additional serology testing based on history and physical examination
– Patients with ILD with suggestive features of connective tissue disease, specific autoantibodies, or ANA >= 1:320 and/or RF positive should have referral to rheumatology
– Bronchoalvelolar lavage (BAL) from bronchoscopy can be helpful for diagnosis in some circumstances such as non-fibrotic ILD, malignancy and infection
– Transbronchial lung biopsy can be helpful in diagnosing some nonfibrosing ILDs (such as sarcoidosis) and to identify malignancy/infection. Risks including bleeding and pneumothorax in those with fibrotic ILD. Due to risks and low yield, transbronchial biopsy is not routinely done in patients with fibrotic ILD.
There are more details in the CTS position statement linked below on surgical lung biopsy.
Multidisciplinary discussion (MDD) is the gold standard for ILD diagnosis and is an iterative process where patients are reviewed through dynamic dialogue by radiologists, respirologists, and pathologists who are experts in their fields.
4. Diagnosis of Idiopathic Pulmonary Fibrosis (IPF)
IPF is a progressive irreversible condition characterized by fibrosis of the lung parenchyma without a known cause. The diagnosis requires exclusion of other known causes of ILD (domestic and occupational environmental exposures, connective tissue disease, drugs).
It also requires the presence of a UIP (usual interstitial pneumonia) pattern on high-resolution CT. If patients have surgical lung biopsy, there are also combinations of histological pattern from biopsy and CT findings that can make a diagnosis of IPF.
The following table is from the IPF guidelines from 2011 linked below. These are the features on a high-resolution CT that suggest UIP pattern. The second column is a possible UIP pattern. The third column indicates features not consistent with UIP pattern.
5. Management of IPF
Management includes non-pharmacologic and pharmacologic strategies, including:
- Pulmonary rehabilitation
- Vaccinations
- Smoking cessation
- Supplemental oxygen
- Resting hypoxemia (same as COPD)
- Exertional hypoxemia (sat < 88% with improved walk distance or dyspnea on supplemental O2)
- Dyspnea and cough management
- Acute exacerbations (worsened dyspnea/hypoxia with new ground glass opacities on CT) may be treated with steroids and empiric antibiotics (rule out other acute causes such as infection, pulmonary embolism, among others).
- No ongoing corticosteroids or immunosuppression as this increases mortality in IPF
- Refer early for lung transplant where appropriate/meeting criteria
- IPF is treated with anti-fibrotics (pirfenidone, nintedanib) which slow decline in FVC
If you have any questions or comments, feel free to email me at cmr@wchospital.ca!
6. References
- Featured Image from – Shaw, J., Marshall, T., Morris, H., & Chaudhuri, N. (2018). Idiopathic pulmonary fibrosis: a clinical update. British Journal of General Practice. 68 (670): 249-250. DOI: 10.3399/bjgp18X696149
- Cottin, V et al. (2018). Presentation, diagnosis and clinical course of the spectrum of progressive-fibrosing interstitial lung diseases. ERS. 27: 180076; DOI: 10.1183/16000617.0076-2018. https://err.ersjournals.com/content/27/150/180076
- Kerri A. Johannson, Martin Kolb, Charlene D. Fell, Deborah Assayag, Jolen Fisher, Andrew Churg, Kaïssa de Boer, Margaret M. Kelly, Andrew G. Lee, Jonathon Leipsic, Hélène Manganas, Shikha Mittoo, Shane Shapera, Kazuhiro Yasufuku & Christopher J. Ryerson (2017) Evaluation of patients with fibrotic interstitial lung disease: A Canadian Thoracic Society position statement, Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 1:3, 133-141, DOI: 10.1080/24745332.2017.1359056.
- Raghu, G., Collard, H. R., Egan, J. J., Martinez, F. J., Behr, J., Brown, K. K., Colby, T. V., Cordier, J. F., Flaherty, K. R., Lasky, J. A., Lynch, D. A., Ryu, J. H., Swigris, J. J., Wells, A. U., Ancochea, J., Bouros, D., Carvalho, C., Costabel, U., Ebina, M., Hansell, D. M., … ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis (2011). An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. American journal of respiratory and critical care medicine, 183(6), 788–824. https://doi.org/10.1164/rccm.2009-040GL