74 years old male with stress dyspnea

Case provided by Anja

History
74 years old male with stress dyspnea and nonproductive cough. Restrictive ventilation abnormality at lung function testing.

Imaging findings
Conventional x-ray of the chest shows basal-predominant reticular abnormalities with volume loss (A). Computed tomography of the chest shows reticular architectural distortion with thickening of inter- and intralobular septae, traction bronchiectasis, and honeycombing (B, C).

Diagnosis
Idiopathic pulmonary fibrosis (IPF).

Discussion
IPF refers to a clinical syndrome of interstitial lung disease that affects more commonly men than women. The median survival from time of diagnosis varies between 2.5 to 3.5 years. IPF does usually not respond to steroid treatment, in contrast to other interstitial lung diseases.

IPF is associated with the histologic pattern of usual interstitial pneumonia (UIP). UIP pattern corresponds to characteristic imaging findings that are especially salient at computed tomography:

  • Subpleural and basal fibrosis pattern
  • Intralobular reticular opacities with traction bronchiectasis
  • Honeycombing
  • Ground-glass opacities (less extensive than reticular abnormalities)

Honeycombing is the hallmark feature of UIP. It consists of clustered cystic airspaces, typically of diameters in the order of 3 to 10 mm. Ground-glass opacities are a less prominent finding in UIP. However, in acute exacerbation of IPF diffuse or peripheral ground-glass opacities are increasingly present.

Because of the high degree of diagnostic accuracy of CT, the diagnosis of UIP is commonly based on clinical and imaging features alone, without the need for surgical biopsy.

It is the task of the radiologist to discriminate UIP pattern in IPF from other interstitial lung diseases and especially from non-specific interstitial pneumonia (NSIP) pattern. In contrast to UIP, ground-glass opacities (in combination with evidence of fibrosis) are NSIP’s most salient CT features. NSIP is frequently associated with an underlying condition such as collagen-vascular disease, hypersensitivity pneumonitis or pneumotoxic medication. The prognosis of NSIP is substantially better than that of UIP and it responds to steroid treatment. The clinical features of NSIP are similar to those of UIP, except that patients with NSIP are more commonly female and generally have a younger mean age. Because the CT features of NSIP may overlap with those of other interstitial lung diseases (not only UIP, but also other disorders such as organizing pneumonia or desquamative interstitial pneumonia), a surgical lung biopsy should be considered when the imaging pattern suggests NSIP.

Teaching points

  • IPF is an interstitial lung disease characterized by UIP pattern at histology and imaging.
  • The hallmark imaging feature of UIP is fibrosis with honeycombing.
  • The radiologist has to differentiate between UIP and NSIP, the latter of which is associated with fibrosis with ground-glass-opacities.

Recommended reading
Mueller-Mang et al.
What Every Radiologist Should Know about Idiopathic Interstitial Pneumonias
Radiographics (2007) 27:595

Lynch et al.
Idiopathic interstitial pneumonias: CT features.
Radiology (2005) 236:10

Nishino et al.
A practical approach to high-resolution CT of diffuse lung disease
Eur J Radiol (2014) 83:6

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