Interstitial lung disease

Last revised by Muthla Abdulmanan Mohamed on 25 Oct 2023

Interstitial lung disease (ILD) is an umbrella term that encompasses a large number of disorders that are characterized by diffuse cellular infiltrates in a periacinar location. The spectrum of conditions included is broad, ranging from occasional self-limited inflammatory processes to severe debilitating fibrosis of the lungs. 

Interstitial lung disease is considered a misnomer by some, as many of the diseases also involve the alveolar spaces.  

Interstitial lung diseases classically produce the "3Cs": cough, clubbing of the nails, and coarse crackles on auscultation 6.

Functional respiratory tests commonly show an abnormal restrictive pattern and reduced diffusing capacity. 

The radiological appearances are not specific for the underlying cause of diffuse lung disease in many cases. It is therefore key to determine whether there is an underlying cause for the changes. A number of precipitants can cause diffuse interstitial disease such as:

Eliciting a history of underlying systemic disease is also helpful since they may involve the lungs in a diffuse and infiltrative manner. Examples include:

Where a cause is not determined, the idiopathic interstitial pneumonia (IIP) should be considered:

Mnemonic: All Idiopathic Chronic Lung Diseases aRe Nonspecific

The diffuse lung diseases tend to cause infiltrative opacification in the periphery of the lung, but patterns vary among the different etiologies. Please refer to the articles in each specific etiology listed above for specific details on their imaging pattern. 

Follow up and monitoring will depend on a multitude of factors such as symptoms and other co-morbidities etc. While no strict consensus recommendations are available in relation to imaging follow-up for patients with progressive fibrosing forms, many consider an HRCT at the patient’s initial presentation and then every 12–18 months to assess for progression dependent on symptoms etc 11.

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