Pathology, Education and training, Education, Diagnostic procedure, CT, Thorax, Lung
T. D. Melo1, I. Marques2; 1Gondomar/PT, 2Vila Nova de Gaia/PT
Idiopathic pulmonary fibrosis (IPF) is a specific form of chronic,
progressive fibrosing interstitial pneumonia of unknown cause.
The histopathological and radiological patterns of usual interstitial pneumonia (UIP) are associated with IPF.
Many diseases can produce fibrosing interstitial lung disease (ILD).
In order to make the diagnosis of IPF,
alternative causes of fibrosing ILD must be excluded.
It is important to look for connective tissue diseases,
exposure to antigens that might result in hypersensitivity pneumonitis and drug toxicity,
since other diseases may present with radiological UIP pattern.
IPF has been described as a deadly disease,
because progressive decline in pulmonary function eventually leads to death.
in recent years new medical treatments have been approved for IPF,
changing its management.
Many clinical trials have been conducted,
enabling to recognize limitations of the diagnostic criteria available.
Diagnostic approach to IPF is highly dependent on high resolution computed tomography (HRCT) scans,
so high-quality computed tomography (CT) images are essential.
Volumetric HRCT acquisition is preferred,
since it improves detection of abnormalities and enables clear analysis of lesion characteristics and distribution on cross-sectional images and multiplanar reformations. According to the latest guidelines from the American Thoracic Society,
at least two acquisitions should be done:
- The first acquisition must be volumetric in supine position at sustained end-inspiration; Inadequate inspiration increases lung attenuation and may lead to misinterpretation of key findings like ground glass opacity and fine reticulation.
- The second acquisition is obtained in supine position at sustained end-expiration,
after a prolonged expiration,
it can be either volumetric or sequential; Expiratory imaging is useful to identify air trapping (this finding suggests an alternative diagnosis to IPF).
A third acquisition is optional.
It is done in prone position in order to clear position-induced changes in the dependent lung.
it can be limited to the lower lobes and it can be either volumetric or sequential.
This acquisition facilitates the diagnosis of honeycombing.
In 2017 the Fleischner Society presented new diagnostic criteria for IPF.
The American Thoracic Society (ATS),
European Respiratory Society (ERS),
Japanese Respiratory Society (JRS),
and Latin American Thoracic Society (ALAT) published an official clinical practice guideline on the same subject in 2018.
Both documents use four diagnostic categories regarding imaging findings which have a direct implication in patient management and treatment.
Differences between the two documents are highlighted in Table 1.
For our pictorial review we will focus on the Fleischner Society white-paper.