IPF Radiologic Features

Possible Usual Interstitial Pneumonia Pattern on HRCT, Small

Used with permission from McGraw-Hill Companies, Inc. Copyright © 2007 McGraw-Hill Companies, Inc.

Test Your Eyes

High-Resolution Computed Tomography (HRCT)

High-resolution computed tomography (HRCT) allows a detailed examination of the lung parenchyma and should be obtained in the evaluation of all patients with suspected IPF.81238 An HRCT diagnosis of IPF negates the need for surgical lung biopsy, eliminating operative risk.8 In the evaluation of HRCT images, the distribution and predominance of specific features are key factors in making a diagnosis of UIP.39

The HRCT criteria were devised to convey a level of confidence for a radiologic diagnosis of UIP in a patient clinically suspected to have IPF.40

The 2011 ATS/ERS/JRS/ALAT guidelines define specific HRCT features that comprise the criteria for UIP.8 As shown in Table 3, HRCT features are placed in 1 of 3 categories: definite UIP pattern, possible UIP pattern, and inconsistent with UIP pattern.8

Table 3.
HRCT criteria for usual interstitial pneumonia. Reprinted with permission of the American Thoracic Society. Copyright ©2014 American Thoracic Society. Raghu G, Collard HR, Egan JJ, et al. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med. 2011;183:788-824. Official Journal of the American Thoracic Society. Note: this document was published in 2011 and is currently in revision. Certain aspects of this document may be out of date and caution should be used when applying these in clinical practice or other usages.

UIP Pattern
(all 4 features)
Possible UIP Pattern
(all 3 features)
Inconsistent with UIP Pattern
(any of the 7 features)
Subpleural, basal predominance Subpleural, basal predominance Upper or mid-lung predominance
Reticular abnormality Reticular abnormality Peribronchovascular predominance
Honeycombing with or without traction bronchiectasis Absence of features listed as inconsistent with UIP pattern Extensive ground glass abnormality (extent > reticular abnormality)
Absence of features listed as inconsistent with UIP pattern   Profuse micronodules (bilateral, predominately upper lobes)
    Discrete cysts (multiple, bilateral, away from areas of honeycombing)
    Diffuse mosaic attenuation/air-trapping (bilateral, in 3 or more lobes)
    Consolidation in bronchopulmonary
segment(s)/lobe(s)

HRCT, high-resolution computed tomography; UIP, usual interstitial pneumonia. Reprinted with permission of the American Thoracic Society. Copyright © 2014 American Thoracic Society.

UIP Pattern on HRCT

As shown in Figure 2,12 the radiographic features of UIP on HRCT images of the lung are characterized by the presence of a reticular pattern of small interlacing linear opacities, suggestive of a net.84142 These reticular opacities may be associated with traction bronchiectasis.83841

Honeycombing is common and critical for making a definite diagnosis of UIP without surgical biopsy.843 Honeycombing is manifested mainly as subpleural clustered cystic airspaces, usually of comparable diameters, ranging from 3 mm to 10 mm but occasionally as large as 2.5 cm, with well-defined, thickened, shared walls.841 A pattern of ground-glass opacity is possible, but if present it is less extensive than the reticulation.8 The distribution of UIP is characteristically basal and peripheral, though often patchy.839 Together, subpleural basilar reticular changes, honeycombing, and the absence of additional HRCT features considered inconsistent with UIP (Table 3) are diagnostic for IPF, and the patient does not require surgical lung biopsy.8 If honeycombing is not present, a radiologic diagnosis of IPF cannot be confidently made and the patient would require a surgical lung biopsy to confirm IPF diagnosis.8 However, a surgical biopsy may be deferred in such patients due to underlying comorbidities, poor pulmonary function, or patient preference.8

Figure 2.
HRCT image of usual interstitial pneumonia. Reprinted from Fishman's Pulmonary Diseases and Disorders, 4th edition 2007. Meltzer, EB and Noble, PW: Chapter 70, Idiopathic Pulmonary Fibrosis. Used with permission from McGraw-Hill Companies, Inc. Copyright © 2007 McGraw-Hill Companies, Inc.

Usual Interstitial Pneumonia Pattern on HRCT

In the appropriate clinical setting, the presence of a UIP pattern on HRCT images is sufficient to make an accurate diagnosis of IPF, and negates the need for a surgical lung biopsy.8

Possible UIP Pattern on HRCT

As shown in Figure 3,12 if honeycombing is absent but the HRCT features otherwise meet the criteria for UIP (reticular abnormalities with subpleural and basal distribution and the absence of additional HRCT features considered inconsistent with UIP), a radiologic diagnosis of possible UIP is made.8

Honeycombing is critical; in the absence of this specific feature, a surgical lung biopsy is needed to make a definite diagnosis of IPF.8

Figure 3.
HRCT image of possible usual interstitial pneumonia. Reprinted from Fishman's Pulmonary Diseases and Disorders, 4th edition 2007. Meltzer, EB and Noble, PW: Chapter 70, Idiopathic Pulmonary Fibrosis. Used with permission from McGraw-Hill Companies, Inc. Copyright © 2007 McGraw-Hill Companies, Inc.

Possible Usual Interstitial Pneumonia Pattern on HRCT

HRCT Features Inconsistent With UIP Pattern

Certain HRCT features are inconsistent with a UIP pattern, including micronodules, air trapping on expiratory images, cysts that do not meet criteria for honeycomb cysts, extensive ground-glass opacities, lobar or segmental consolidation, peribronchovascular-predominant distribution, or upper or mid-lung distribution.839 The presence of any of these features should lead to the consideration of an alternative diagnosis.8

In patients clinically suspected to have IPF who demonstrate features that meet the criteria for possible UIP or inconsistent with UIP pattern on HRCT images, additional diagnostic evaluation is needed.8

Content contributed by:
Ryan Hadley, MD
University of Michigan