Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis

C. Nicholas Fetko, MD

Aqeel A. Chowdhry, MD

Tan-Lucien H. Mohammed, MD, FCCP

Axial HRCT shows the typical pattern of severe peripheral honeycombing image and traction bronchiectasis image in idiopathic pulmonary fibrosis.

Coronal HRCT reconstruction shows basilar honeycombing image. Ground-glass opacities are minimal, and the lower lobes have lost volume.


Abbreviations and Synonyms

  • Idiopathic pulmonary fibrosis (IPF), cryptogenic fibrosing alveolitis (CFA), usual interstitial pneumonia (UIP)


  • Most common form of idiopathic interstitial pneumonias

    • Associated with histologic pattern of usual interstitial pneumonia on surgical biopsy


General Features

  • Best diagnostic clue: Subpleural and basal honeycombing and traction bronchiectasis

  • Patient position/location

    • Subpleural and basilar lung

      • Costophrenic angles should be most affected portion of lungs

  • Morphology

    • Reticular opacities, honeycombing, traction bronchiectasis

    • Relative lack of ground-glass opacities

CT Findings

  • Morphology

    • Predominant reticular pattern with honeycombing

      • Peripheral honeycomb cysts may vary in size, dependent on phase of respiratory cycle

      • Traction bronchiectasis or bronchiolectasis essential to diagnosis

    • Ground-glass opacities

      • Reticular opacities > > ground-glass opacities

      • Minor component of overall pattern

    • Emphysema: Coexistent centrilobular or paraseptal emphysema in about 30%

    • Pulmonary ossification may occur in long-standing fibrosis

    • Consider alternative diagnosis to IPF if centrilobular nodules, cysts, extensive ground-glass opacities, consolidation, peribronchovascular distribution

  • Distribution

    • Basal and peripheral predominance

    • Patchy, heterogeneous distribution abuts normal lung

    • May be asymmetric, but not unilateral

    • Mean extent of disease 25% ± 10%

  • Volume loss prominent with honeycombing

  • Pulmonary artery enlargement

    • Reflects pulmonary artery hypertension seen in 50% of those undergoing pre-transplant evaluation

    • Other findings include right ventricular wall hypertrophy, dilatation of right ventricle and atrium, contrast reflux into inferior vena cava, and hepatic veins

  • Adenopathy (50%)

    • Mediastinal lymph node enlargement < 2 cm short axis diameter

    • Most common location right paratracheal nodal station (American Thoracic Society [ATS] region 4) or subcarinal (ATS region 7)

    • Frequency related to extent of fibrosis and duration of disease

  • Complications

    • Acute exacerbation

      • Morphology: New ground-glass opacities or consolidation

      • Distribution: Peripheral (60%), diffuse (25%), multifocal (15%)

      • Generally spares honeycomb lung

    • Bronchogenic carcinoma

      • Seen in up to 10% of patients with long-standing IPF

      • Typical appearance: Focal consolidation in periphery of lower lobes in area of severe fibrosis

      • May be multiple

    • Barotrauma: Increased risk for pneumothorax, pneumomediastinum

    • Infection: Higher risk for mycobacterial species, Aspergillus, and other organisms

      • Suspect infection with progressive consolidation or cavitation

  • Accuracy

    • Should make confident diagnosis in 50% of cases

    • Positive predictive value of confident diagnosis = 95-100%

      • Interestingly, interobserver agreement of presence of honeycombing only about 70%

Radiographic Findings

  • Radiography: Not as specific as CT but usually abnormal

Imaging Recommendations

  • Best imaging tool: HRCT to detect and characterize interstitial lung disease


Nonspecific Interstitial Pneumonitis

  • Ground-glass opacities > > reticular pattern

  • Traction bronchiectasis out of proportion to extent of reticular opacities

  • Bronchovascular distribution more common

  • Honeycombing not as prominent

  • Traction bronchiectasis extends into more central airways with IPF


  • Subpleural reticular pattern with honeycombing identical to IPF

  • Fibrosis in asbestosis may be coarser than in IPF

  • Subpleural curvilinear lines, mosaic perfusion, and parenchymal bands more common

  • Associated (calcified) pleural plaques

  • Bronchiolectasis more common in IPF

Chronic Hypersensitivity Pneumonitis

  • Inferior costophrenic angles not most severely involved lung (usually mid and upper lung)

  • Centrilobular nodules, lobular air-trapping more common

Rheumatoid Arthritis

  • Pulmonary fibrosis difficult to distinguish from IPF

  • Erosive arthritis not seen with IPF

  • More frequently associated with nonspecific interstitial pneumonia (NSIP) pattern

Systemic Sclerosis

  • Basilar predominant pulmonary fibrosis

  • Dilated esophagus not seen with IPF

  • Subcutaneous calcifications distinguish from IPF

  • More frequently associated with NSIP pattern

Drug Reaction

  • Can cause similar radiographic abnormalities

  • Typical drugs: Nitrofurantoin (Macrodantin) and chemotherapy drugs


  • Typically causes bronchocentric fibrosis in upper lung zones

  • Some have pattern indistinguishable from IPF

  • Can be associated with mediastinal and hilar adenopathy

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Idiopathic Pulmonary Fibrosis
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