1. Interstitial Lung Disease (ILD)

2. What is the lung interstitium?
It is all the structures that support the lung tissue. The interstitium includes:
Fibrous septae
Alveolar walls
Lymphatics
Pulmonary vessels

3. What are the causes of abnormal Interstitial Shadowing on a CXR?
There are many causes!
Two important ones are:
Idiopathic
leading to idiopathic pulmonary fibrosis / fibrosing alveolitis
Cardiogenic intersitial pulmonary oedema
see pulmonary oedema presentation
There are many other causes
E.g. Drugs, asbestosis, farmer’s lung

4. What happens when there is ILD?
Interstitial structures become thickened / inflamed
This occurs in an irregular fashion – some structures will initially remain normal while others will become inflamed
Interstitial structures that are normally too small to be seen with the naked eye on CXR eventually become large enough to be visible

5. What does ILD look like? ILD can include some or all of:
Fine lines (reticular shadowing)
Small nodules
Larger nodules
Lung volume loss
Honeycombing
Fibrosis
A good place to look for ILD is between rib spaces; close to the chest wall, there should normally be very few lung markings, and certainly no nodules or fine lines

6. Idiopathic Pulmonary Fibrosis

7. Idiopathic Pulmonary Fibrosis
Reticulonoduar shadowing
Irregular heart border

8. Idiopathic Pulmonary Fibrosis
This patient also has lung cancer (a complication of pulmonary fibrosis)

9. How can ILD be investigated?
High resolution CT chest
Some causes have specific appearances
Pulmonary function tests
Lung Biopsy
Blood tests
…the choice of tests depends on the clinical presentation

10. Take Home Points
Interstitial lung disease has a characteristic appearance on a CXR
Look between rib spaces for the presence of extra nodules and fine lines
High resolution CT chest is a useful test to evaluate suspected cases of ILD