High resolution CT scanning and IPF

With the recent arrival of a new CT scanner in Hamilton, I've been reading an article in this month's Respirology journal by a group from the University of Michigan. This review recaps evidence and their clinical practice when it comes to diagnosis of idiopathic pulmonary fibrosis.

An editorial in the same journal reiterates that there are, as yet, no proven treatments for this condition - although colleagues at the Royal Melbourne Hospital and The Alfred Hospital in Melbourne are currently participating in a trial of two novel endothelin receptor antagonists (like Bosentan, currently used to trat pulmonary hypertension) in IPF. (These trials are currently enrolling patients with IPF, with minimal honeycomb change and with a forced vital capacity on spirometry of over 50% predicted).

Idiopathic pulmonary fibrosis is a diagnosis now often made without lung biopsy. A multidisciplinary evaluation must exclude known causes of pulmonary fibrosis which can result in the same radiological appearance - such as pulmonary fibrosis associated with connective tissue disease (eg rheumatoid arthritis or scleroderma); chronic hypersensitivity pneumonitis; or asbestosis - and must include a high resolution CT scan of the chest. If the CT appearance is agreed to demonstrate features of usual interstitial pneumonia - which is the pathological/radiological appearance in idiopathic pulmonary fibrosis - in the absence of an underlying cause then IPF is diagnosed.

As simple as that! The major centres / city hospitals tell us, however, that there is a lot of operator variability outside of the major centres. Which means that it is important for people with this condition to be evaluated in an environment where people really know their stuff. Or perhaps, according to the major centres, all patients with IPF should be evaluated in the major centres.

The following table was offered as, in my opinion, a quite useful summary of the important radiological features of usual interstitial pneumonia:

Definite usual interstitial pneumonia

• subpleural basal distribution
• predominant honeycomb
• interlobular septal thickening
• traction bronchiectasis
• no predominant ground glass attenuation

Consistent with usual interstitial pneumonia

• subpleural, basal distribution
• minimal or equivocal honeycomb
• interlobular septal thickening
• traction bronchiectasis
• no predominant ground glass attenuation

Suggestive of alternate diagnosis

• No honeycomb, with one or more of the following as the predominant HRCT finding;
• upper or mid lung distribution
• peribronchovascular distribution
• ground glass attenuation
• micronodules
• discrete cysts
• air trapping
• consolidation

This seems to be the poster they hang on the wall of the registrars' reporting room at Ann Arbor. I'll have to run it past my local radiology colleagues and see what they think - but it looks pretty good to me.

Supports for patients with a diagnosis of pulmonary fibrosis are lacking in the Australian community. The Pulmonary Fibrosis Foundation in the USA runs a pretty informative website and supports good research. I am not aware of a comparable group in Australia.

Andrew