Usual interstitial pneumonia: typical, possible, and "inconsistent" patterns

Our plain-English summary of Usual interstitial pneumonia: typical, possible, and "inconsistent" patterns, by P.P.T.E.S. Torres, M.F. Rabahi, M.A.C. Moreira, et al (Jornal Brasileiro de Pneumologia, 2017).

The study

• Authors: P.P.T.E.S. Torres, M.F. Rabahi, M.A.C. Moreira, G.S.P. Meirelles, E. Marchiori
• Journal: Jornal Brasileiro de Pneumologia
• Published: 2017;43(5):393-398
• Language: Portuguese
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Idiopathic pulmonary fibrosis is a severe and progressive chronic fibrosing interstitial lung disease, a definitive diagnosis being established by specific combinations of clinical, radiological, and pathological findings. According to current international guidelines, HRCT plays a key role in establishing a diagnosis of usual interstitial pneumonia (UIP). Current guidelines describe three UIP patterns based on HRCT findings: a typical UIP pattern; a pattern designated "possible UIP"; and a pattern designated "inconsistent with UIP", each pattern having important diagnostic implications. A typical UIP pattern on HRCT is highly accurate for the presence of histopathological UIP, being currently considered to be diagnostic of UIP. The remaining patterns require further diagnostic investigation. Other known causes of a UIP pattern include drug-induced interstitial lung disease, chronic hypersensitivity pneumonitis, occupational diseases (e.g., asbestosis), and connective tissue diseases, all of which should be included in the clinical differential diagnosis. Given the importance of CT studies in establishing a diagnosis and the possibility of interobserver variability, the objective of this pictorial essay was to illustrate all three UIP patterns on HRCT.

In plain English

This article was a pictorial essay, not an original study. Authors at Brazilian institutions used patients' CT images to illustrate how international guidelines sort high-resolution CT findings of usual interstitial pneumonia (UIP), the scarring pattern underlying idiopathic pulmonary fibrosis, into three patterns. A "typical" pattern showed scarring mainly in the lower, outer lungs with honeycombing (clusters of small cysts) and none of the findings considered inconsistent with UIP. Guidelines consider this diagnostic without surgical lung biopsy. A "possible" pattern had similar scarring, no honeycombing and none of the inconsistent findings. Inconsistent findings included middle and upper lung predominance, ground-glass opacity more extensive than scarring, and bilateral air trapping across three or more lobes. Its illustrated examples came from patients with chronic hypersensitivity pneumonitis or sarcoidosis. The possible and inconsistent patterns require surgical lung biopsy under the guidelines. The authors discussed scan technique, recognising honeycombing, and other studies of radiologist disagreement. Asbestosis appeared only as one known cause of a UIP pattern; asbestos exposure was not studied. The authors concluded that radiologists must be familiar with all UIP patterns and describe them accurately.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Pictorial essay (descriptive, illustrated review of CT criteria from current guidelines); no original data collection or statistical analysis
• Who was studied: No study population. Illustrative CT images of individual patients: a 77-year-old female (typical UIP), a 75-year-old male (possible UIP), and 38-, 61- and 63-year-old female patients (inconsistent with UIP, diagnosed with chronic hypersensitivity pneumonitis or sarcoidosis). The work was carried out at Multimagem Diagnósticos and the Universidade Federal de Goiás, Goiânia, Brazil.
• Exposure: No exposure was studied. Asbestosis was mentioned only as one of several known causes of a UIP pattern, alongside drug-induced lung disease, hypersensitivity pneumonitis and connective tissue diseases. No fiber type is named.
• Main results:
  • The typical UIP pattern on HRCT has three parts: scarring (reticular opacities) mainly at the lung bases and periphery, honeycombing (with or without traction bronchiolectasis), and absence of all findings considered inconsistent with UIP. Under the guidelines this is considered diagnostic without surgical lung biopsy.
  • The possible UIP pattern consists of predominantly basal and peripheral reticular opacities, with no honeycombing and none of the findings considered inconsistent with UIP. Its main differential diagnosis is fibrotic nonspecific interstitial pneumonia (NSIP).
  • The findings listed as inconsistent with UIP are:
• disease mainly in the middle and upper lung fields
• peribronchovascular predominance
• ground-glass opacity more extensive than reticular opacities
• bilateral scattered micronodules, mainly in the upper lung fields
• multiple bilateral cysts away from areas of fibrosis
• mosaic perfusion or air trapping, bilateral and in three or more lobes
• consolidations

Several of these suggest chronic hypersensitivity pneumonitis.

• The described diagnostic criteria for honeycombing are mainly subpleural cysts 3 to 10 mm across, with relatively thick (1 to 3 mm) shared walls, grouped in layers, with emphysema excluded. In one illustrated case, suspected honeycombing turned out to be traction bronchiectasis.
• One illustrated patient's CT findings met possible UIP criteria initially and typical UIP criteria on follow-up six years later. The authors noted that CT interpretation can change over time.
• The authors' conclusion: The authors concluded that radiologists must be familiar with all UIP patterns and be able to describe them accurately in reports and multidisciplinary meetings, particularly given antifibrotic treatment for idiopathic pulmonary fibrosis.

Topics

Medical terms in this study, explained in our Lexicon: Interstitial, Idiopathic, Pulmonary Fibrosis, Interstitial Lung Disease, High-Resolution CT (HRCT), Pneumonitis, Occupational Disease, Differential Diagnosis.

Related studies

• Differential diagnosis of usual interstitial pneumonia: when is it truly idiopathic? — W.A. Wuyts, A. Cavazza, et al. (2014)
• Usual interstitial pneumonia in asbestos-exposed cohorts - concurrent idiopathic pulmonary fibrosis or atypical asbestosis? — R.L. Attanoos, F.S. Alchami, et al. (2016)
• Disease progression in patients with usual interstitial pneumonia and probable UIP patterns on computed tomography with various underlying etiologies: a retrospective cohort study — S. Yang, J. Wang, et al. (2023)
• Dyskeratosis congenita showing usual interstitial pneumonia — S. Imokawa, A. Sato, et al. (1994)
• Asbestosis and environmental causes of usual interstitial pneumonia — M. Gulati, C.A. Redlich (2015)
• Asbestos exposure increases the incidence of histologically confirmed usual interstitial pneumonia — Y. Kawabata, Y. Shimizu, et al. (2016)

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