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. 2017 Sep-Oct;43(5):393–398. doi: 10.1590/S1806-37562016000000368
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Usual interstitial pneumonia: typical, possible, and “inconsistent” patterns

Pedro Paulo Teixeira e Silva Torres 1, Marcelo Fouad Rabahi 2, Maria Auxiliadora Carmo Moreira 2, Gustavo de Souza Portes Meirelles 3, Edson Marchiori 4
PMCID: PMC5790657  PMID: 29160385

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.

Keywords: Tomography, X-ray computed; Lung diseases, interstitial; Pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrosing interstitial lung disease that is usually progressive. Recently defined diagnostic criteria include exclusion of other known causes of interstitial lung disease, the presence of a usual interstitial pneumonia (UIP) pattern on HRCT, and specific combinations of HRCT and surgical lung biopsy patterns.1,2

A typical UIP pattern on HRCT has been shown to be highly accurate for the presence of a UIP pattern on surgical lung biopsy (90-100%); reliable imaging features of UIP are currently considered to be diagnostic of a UIP pattern, without the need for a surgical lung biopsy.1 Surgical lung biopsy is currently recommended when HRCT findings are not typical of UIP, a definitive diagnosis being established by specific combinations of imaging and histopathological findings.1 Therefore, correct interpretation of HRCT findings is essential for a definitive diagnosis, particularly in view of the fact that antifibrotic agents have recently been approved for use in the treatment of IPF.3

Current guidelines describe three UIP patterns based on HRCT findings: a typical UIP pattern (which eliminates the need for surgical lung biopsy); a pattern designated “possible UIP”; and a pattern designated “inconsistent with UIP”, surgical lung biopsy being required in patients presenting with either of the last two patterns.1,2,4 The objective of the present study was to describe and illustrate the criteria for classifying patients as having a typical UIP pattern, a possible UIP pattern, or an inconsistent with UIP pattern.

HRCT FEATURES CHARACTERIZING UIP PATTERNS

Typical UIP pattern

A typical UIP pattern on HRCT consists of predominantly basal and peripheral reticular opacities and honeycombing, with or without traction bronchiolectasis. In addition, all of the findings that are considered to be inconsistent with UIP must be absent (Figure 1).1 When all of the aforementioned criteria are met, the findings are considered to be pathognomonic for UIP, eliminating the need for a surgical lung biopsy.1 There is good interobserver agreement among radiologists for typical UIP findings.5,6 It is of note that UIP and IPF are not synonyms, known causes of a UIP pattern including drug-induced interstitial lung disease, occupational diseases (e.g., asbestosis), hypersensitivity pneumonitis, and connective tissue diseases.5

Figure 1. A 77-year-old female patient presenting with a typical usual interstitial pneumonia pattern. In A, axial CT scans of the chest with lung window settings, showing reticular opacities, traction bronchiectasis, and extensive honeycombing. In B, coronal reformatted CT images showing an apicobasal gradient of involvement.

Figure 1

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Possible UIP pattern

A possible UIP pattern consists of predominantly basal and peripheral reticular opacities and no honeycombing or any of the findings that are considered to be inconsistent with UIP (Figure 2).1 A possible UIP pattern is less specific for UIP than is a typical UIP pattern, the main differential diagnosis being with fibrotic nonspecific interstitial pneumonia (NSIP).5 No honeycombing, extensive ground-glass opacity, subpleural sparing, and lower lobe volume loss are suggestive of NSIP.7-9 Honeycombing is rare in cases of NSIP, having been found in less than 5% of the patients with idiopathic NSIP investigated in one study.7

Figure 2. A 75-year-old male patient presenting with a possible usual interstitial pneumonia pattern. Axial CT scan of the chest with lung window settings (in A) and coronal reformatted CT image (in B) showing peripheral reticular opacities and traction bronchiolectasis (in A) and an apicobasal gradient (in B), without honeycombing.

Figure 2

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Inconsistent with UIP pattern

Findings that are considered to be inconsistent with UIP include a) longitudinal disease distribution in the middle and upper lung fields; b) peribronchovascular predominance of changes in the axial axis (Figure 3); c) extensive ground-glass opacity, the extent of which is greater than that of reticular opacities; d) bilateral scattered micronodules predominantly in the upper lung fields (Figure 4); e) cysts (multiple, bilateral, away from areas of fibrosis); f) a mosaic perfusion pattern/air trapping (bilateral, in three or more lobes; Figure 5); and g) consolidations. Several of the aforementioned findings are suggestive of chronic hypersensitivity pneumonitis (CHP), further investigation being required for a differential diagnosis.5

Figure 3. A 38-year-old female patient presenting with an inconsistent with usual interstitial pneumonia pattern and diagnosed with chronic hypersensitivity pneumonitis. Axial HRCT scan of the chest with lung window settings, showing diffuse reticular opacities with traction bronchiolectasis. Note severe peribronchovascular bundle involvement in the right upper lobe (arrow).

Figure 3

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Figure 4. A 63-year-old female patient presenting with an inconsistent with usual interstitial pneumonia pattern and diagnosed with sarcoidosis. Axial HRCT scan of the chest with lung window settings, showing confluent, predominantly peribronchovascular reticular opacities with characteristics of micronodules with a perilymphatic distribution (arrows).

Figure 4

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Figure 5. A 61-year-old female patient presenting with an inconsistent with usual interstitial pneumonia pattern and diagnosed with chronic hypersensitivity pneumonitis. Axial HRCT scans of the chest with lung window settings, showing diffuse reticular opacities, as well as areas of ground-glass attenuation associated with areas of decreased attenuation (arrows), characterizing a mosaic pattern.

Figure 5

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SPECIAL CONSIDERATIONS

Technical aspects

Technically satisfactory image acquisition is required for a correct diagnosis, minimum technical requirements including a) images acquired at full inhalation, without motion artifacts; b) thin, sequential or volumetric axial images with a reconstruction interval ≤ 2 cm; c) slice thickness ≤ 2 mm; d) use of a high-resolution algorithm; e) a field of view optimized to include only lung parenchyma; f) images acquired during exhalation are useful for defining air trapping; g) use of the prone position in case of uncertainty regarding position-dependent opacities; and h) use of multiplanar reconstructions of volume acquisition CT images.10

Inadequately performed inspiratory maneuvers can result in increased/heterogeneous lung attenuation and motion artifacts that can adversely affect CT studies (Figure 6). Suggestions for improving the quality of CT studies include the use of simple, clear instructions on how to perform inspiratory/expiratory maneuvers, patient training in different breathing levels before image acquisition, and the use of rest periods during sequential acquisitions.10

Figure 6. Axial CT scans of the chest with lung window settings. In A, scan taken during an inadequately performed inspiratory maneuver, the resulting image resembling diffuse ground-glass opacity. In B, a new scan, taken during an adequately performed inspiratory maneuver.

Figure 6

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Diagnosis of honeycombing

A correct CT diagnosis of honeycombing is a crucial step in identifying a typical UIP pattern and establishing a clinical and imaging diagnosis of IPF.1 However, even among evaluators with extensive experience in interstitial lung disease, there is significant interobserver variability in attempts to detect honeycombing and differentiate it from other findings, such as traction bronchiectasis, cystic disease, and pulmonary emphysema (Figure 7).11 Diagnostic criteria for honeycombing include predominantly subpleural cysts of 3-10 mm in diameter, sharing relatively thick (1-3 mm) walls and grouped on layers, and the exclusion of emphysema.11,12

Figure 7. In A, axial HRCT scan of the chest with lung window settings. In B, coronal reformatted CT image (minimum intensity projection). In A, images suggestive of a cluster of subpleural cysts (arrows), suspected of being honeycombing but found to be traction bronchiectasis (arrows) on oblique coronal reformatted CT images (in B).

Figure 7

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Interobserver agreement: CT criteria for UIP patterns

Walsh et al.13 evaluated interobserver agreement for the current criteria for a UIP pattern on CT. Interobserver agreement was found to be only moderate for experienced general radiologists and thoracic radiologists, the difficulty in distinguishing among UIP patterns being attributed to discrepancies regarding the presence and distribution of honeycombing.

Atypical patterns and differential diagnosis

Although typical CT findings of UIP can predict a histopathological diagnosis of UIP, they are absent in up to 30% of patients.14 Sverzellati et al.14 studied histopathologically confirmed cases of UIP and found that radiologists made an alternative diagnosis in 62% of the cases. The aforementioned study14 shows that, although CT is highly accurate in diagnosing UIP in typical situations, CT studies should not be used in order to exclude the possibility of UIP. In atypical cases, first-choice diagnoses include NSIP, CHP, sarcoidosis, and chronic organizing pneumonia.

Temporal evolution

The clinical course of IPF is variable and unpredictable at the time of diagnosis; although most patients experience a slow progressive decline, some remain stable, whereas others experience a rapid decline.1,15 With regard to the severity of HRCT findings, areas of ground-glass attenuation usually progress to reticular opacities, which in turn progress to honeycombing, the extent of which increases over time.16 It is of note that CT interpretation changes over time, meaning that a possible UIP pattern can progress to a typical UIP pattern (Figure 8).

Figure 8. Axial HRCT scans of the chest with lung window settings, showing the right lower lobe. In A, initial CT findings meeting the criteria for possible usual interstitial pneumonia (UIP), i.e., reticular opacities and ground-glass attenuation, without honeycombing. In B, follow-up CT findings six years later, meeting the criteria for a typical UIP pattern, with disease progression and honeycombing.

Figure 8

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Future directions

The risks of performing a surgical lung biopsy in patients with interstitial lung disease should be taken into consideration; in many cases, diagnosis and treatment are delayed because patient clinical status is a contraindication to biopsy.17,18 Therefore, there is a growing interest in the noninvasive diagnosis of IPF, particularly in cases of patients presenting with CT findings of possible UIP. Recent studies comparing IPF patients with a typical UIP pattern and those with a possible UIP pattern have shown clinical and functional similarities between the two groups of patients, as well as showing evidence of a comparable response to antifibrotic treatment with nintedanib.19-21 Several studies investigating patients with IPF have shown high rates of biopsy-proven UIP in those with a possible UIP pattern.22-25 Age at disease onset and the extent of fibrosis on initial HRCT scans have been significantly related to a high probability of IPF, a possible UIP pattern being suggestive of a clinical and radiological diagnosis of IPF in the following cases: a) typical clinical and demographic presentation (i.e., patients over 60 years of age presenting with dyspnea on exertion and pulmonary fibrosis of indeterminate etiology), as determined by a specialist in interstitial lung diseases; and b) imaging findings of possible UIP, according to a specialist in interstitial imaging.24,26

It is of note that some of the studies suggesting that CT findings of possible UIP are sufficient for a diagnosis of IPF derived from clinical trials in which the prevalence of IPF was high, meaning that the results might have been overestimated.23,24 In a study conducted by Brownell et al.,25 it was found that a possible UIP pattern is highly specific for UIP on biopsy; however, the positive predictive value of that pattern is directly related to the prevalence of IPF in the study population. Therefore, according to the authors, a possible UIP pattern on HRCT should not be regarded as confirmatory of histopathological UIP in populations in whom the prevalence of IPF is low or indeterminate.25 Given that the prevalence of CHP is high (i.e., as high as 15%) in Brazil, studies are needed in order to determine the prevalence of IPF in patients with possible UIP before a decision can be made regarding the need for biopsy in such patients.27

Noninvasive diagnostic algorithms for CHP have been proposed, including a typical CT pattern, lymphocytosis in BAL fluid (lymphocyte count > 20-30%), and identification of a causal relationship; such algorithms are extremely useful in the diagnosis of fibrotic interstitial lung diseases, given that the differential diagnosis between CHP and IPF is often difficult.27,28

FINAL CONSIDERATIONS

Of all idiopathic interstitial lung diseases, IPF is the most common; it has a poor prognosis in most cases, and the histopathological substrate of IPF is UIP.29 In a recent review of the diagnostic algorithm for IPF, HRCT was shown to play an indispensable role in characterizing UIP, typical findings being diagnostic of UIP and atypical findings requiring histopathological analysis.1 For a definitive diagnosis, radiologists must be familiar with all UIP patterns and must be able to describe them accurately when writing radiological reports or participating in multidisciplinary meetings, particularly in view of current perspectives on the treatment of IPF, with the use of antifibrotic agents.

1

Study carried out at Multimagem Diagnósticos and at the Universidade Federal de Goiás, Goiânia (GO) Brasil.

Financial support: None.

REFERENCES

  • 1.1 Raghu G, Collard HR, Egan JJ, Martinez FJ, Behr J, Brown KK, 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(6):788-824. https://doi.org/10.1164/rccm.2009-040GL [DOI] [PMC free article] [PubMed]; Raghu G, Collard HR, Egan JJ, Martinez FJ, Behr J, Brown KK. 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(6):788–824. doi: 10.1164/rccm.2009-040GL. https://doi.org/10.1164/rccm.2009-040GL [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.2 Baddini-Martinez J, Baldi BG, Costa CH, Jezler S, Lima MS, Rufino R. Update on diagnosis and treatment of idiopathic pulmonary fibrosis. J Bras Pneumol. 2015;41(5):454-66. https://doi.org/10.1590/S1806-37132015000000152 [DOI] [PMC free article] [PubMed]; Baddini-Martinez J, Baldi BG, Costa CH, Jezler S, Lima MS, Rufino R. Update on diagnosis and treatment of idiopathic pulmonary fibrosis. J Bras Pneumol. 2015;41(5):454–466. doi: 10.1590/S1806-37132015000000152. https://doi.org/10.1590/S1806-37132015000000152 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.3 Raghu G, Rochwerg B, Zhang Y, Garcia CA, Azuma A, Behr J, et al. An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline: Treatment of Idiopathic Pulmonary Fibrosis. An Update of the 2011 Clinical Practice Guideline. Am J Respir Crit Care Med. 2015;192(2):e3-19. https://doi.org/10.1164/rccm.201506-1063ST [DOI] [PubMed]; Raghu G, Rochwerg B, Zhang Y, Garcia CA, Azuma A, Behr J. An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline Treatment of Idiopathic Pulmonary Fibrosis. An Update of the 2011 Clinical Practice Guideline. Am J Respir Crit Care Med. 2015;192(2):e3–19. doi: 10.1164/rccm.201506-1063ST. https://doi.org/10.1164/rccm.201506-1063ST [DOI] [PubMed] [Google Scholar]
  • 4.4 Travis WD, Costabel U, Hansell DM, King Jr TE, Lynch DA, Nicholson AG, et al. An official American Thoracic Society/European Respiratory Society statement: Update of the international multidisciplinary classification of the idiopathic interstitial pneumonias. Am J Respir Crit Care Med. 2013;188(6),733-48. https://doi.org/10.1164/rccm.201308-1483ST [DOI] [PMC free article] [PubMed]; Travis WD, Costabel U, Hansell DM, King TE, Jr, Lynch DA, Nicholson AG, et al. An official American Thoracic Society/European Respiratory Society statement: Update of the international multidisciplinary classification of the idiopathic interstitial pneumonias. Am J Respir Crit Care Med. 2013;188(6):733–748. doi: 10.1164/rccm.201308-1483ST. https://doi.org/10.1164/rccm.201308-1483ST [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.5 Hodnett PA, Naidich DP. Fibrosing interstitial lung disease. A practical high-resolution computed tomography-based approach to diagnosis and management and a review of the literature. Am J Resp Crit Care Med. 2013;188(2):141-9. https://doi.org/10.1164/rccm.201208-1544CI [DOI] [PubMed]; Hodnett PA, Naidich DP. Fibrosing interstitial lung disease A practical high-resolution computed tomography-based approach to diagnosis and management and a review of the literature. Am J Resp Crit Care Med. 2013;188(2):141–149. doi: 10.1164/rccm.201208-1544CI. https://doi.org/10.1164/rccm.201208-1544CI [DOI] [PubMed] [Google Scholar]
  • 6.6 Flaherty KR, Thwaite EL, Kazerooni EA, Gross BH, Toews GB, Colby TV, et al. Radiological versus histological diagnosis in UIP and NSIP: survival implications. Thorax. 2003;58(2):143-8. https://doi.org/10.1136/thorax.58.2.143 [DOI] [PMC free article] [PubMed]; Flaherty KR, Thwaite EL, Kazerooni EA, Gross BH, Toews GB, Colby TV. Radiological versus histological diagnosis in UIP and NSIP survival implications. Thorax. 2003;58(2):143–148. doi: 10.1136/thorax.58.2.143. https://doi.org/10.1136/thorax.58.2.143 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.7 Travis WD, Hunninghake G, King TE Jr, Lynch DA, Colby TV, Galvin JR, et al. Idiopathic nonspecific interstitial pneumonia: report of an American Thoracic Society project. Am J Respir Crit Care Med. 2008;177(12):1338-47. https://doi.org/10.1164/rccm.200611-1685OC [DOI] [PubMed]; Travis WD, Hunninghake G, King TE, Jr, Lynch DA, Colby TV, Galvin JR. Idiopathic nonspecific interstitial pneumonia report of an American Thoracic Society project. Am J Respir Crit Care Med. 2008;177(12):1338–1347. doi: 10.1164/rccm.200611-1685OC. https://doi.org/10.1164/rccm.200611-1685OC [DOI] [PubMed] [Google Scholar]
  • 8.8 Silva CI, Müller NL, Lynch DA, Curran-Everett D, Brown KK, Lee KS, et al. Chronic hypersensitivity pneumonitis: differentiation from idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia by using thin-section CT. Radiology. 2008;246(1):288-97. https://doi.org/10.1148/radiol.2453061881 [DOI] [PubMed]; Silva CI, Müller NL, Lynch DA, Curran-Everett D, Brown KK, Lee KS. Chronic hypersensitivity pneumonitis differentiation from idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia by using thin-section CT. Radiology. 2008;246(1):288–297. doi: 10.1148/radiol.2453061881. https://doi.org/10.1148/radiol.2453061881 [DOI] [PubMed] [Google Scholar]
  • 9.9 Sumikawa H, Jonkoh T, Fujimoto K, Arakawa H, Colby TV, Fukuoka J, et al. Pathologically proved nonspecific interstitial pneumonia: CT pattern analysis as compared with usual interstitial pneumonia CT pattern. Radiology. 2014;272(2):549-56. https://doi.org/10.1148/radiol.14130853 [DOI] [PubMed]; Sumikawa H, Jonkoh T, Fujimoto K, Arakawa H, Colby TV, Fukuoka J. Pathologically proved nonspecific interstitial pneumonia CT pattern analysis as compared with usual interstitial pneumonia CT pattern. Radiology. 2014;272(2):549–556. doi: 10.1148/radiol.14130853. https://doi.org/10.1148/radiol.14130853 [DOI] [PubMed] [Google Scholar]
  • 10.10 Bankier AA, O'Donnell CR, Boiselle PM. Quality initiatives. Respiratory instructions for CT examinations of the lungs: a hands-on guide. Radiographics. 2008;28(4):919-31. https://doi.org/10.1148/rg.284085035 [DOI] [PubMed]; Bankier AA, O'Donnell CR, Boiselle PM. Quality initiatives Respiratory instructions for CT examinations of the lungs: a hands-on guide. Radiographics. 2008;28(4):919–931. doi: 10.1148/rg.284085035. https://doi.org/10.1148/rg.284085035 [DOI] [PubMed] [Google Scholar]
  • 11.11 Watadani T, Sakai F, Johkon T, Noma S, Akira M, Fujimoto K, et al. Interobserver variability in the CT assessment of honeycombing in the lungs. Radiology. 2013;266(3):936-44. https://doi.org/10.1148/radiol.12112516 [DOI] [PubMed]; Watadani T, Sakai F, Johkon T, Noma S, Akira M, Fujimoto K. Interobserver variability in the CT assessment of honeycombing in the lungs. Radiology. 2013;266(3):936–944. doi: 10.1148/radiol.12112516. https://doi.org/10.1148/radiol.12112516 [DOI] [PubMed] [Google Scholar]
  • 12.12 Silva CI, Marchiori E, Souza Júnior AS, Müller NL; Comissão de Imagem da Sociedade Brasileira de Pneumologia e Tisiologia. Illustrated Brazilian consensus of terms and fundamental patterns in chest CT scans. J Bras Pneumol. 2010;36(1):99-123. https://doi.org/10.1590/S1806-37132010000100016 [DOI] [PubMed]; Silva CI, Marchiori E, Souza AS, Júnior, Müller NL. Comissão de Imagem da Sociedade Brasileira de Pneumologia e Tisiologia Illustrated Brazilian consensus of terms and fundamental patterns in chest CT scans. J Bras Pneumol. 2010;36(1):99–123. doi: 10.1590/s1806-37132010000100016. https://doi.org/10.1590/S1806-37132010000100016 [DOI] [PubMed] [Google Scholar]
  • 13.13 Walsh SL, Calandriello L, Sverzellati N, Wells AU, Hansell DM; UIP Observer Consort. Interobserver agreement for the ATS/ERS/JRS/ALAT criteria for a UIP pattern on CT. Thorax. 2016;71(1):45-51. https://doi.org/10.1136/thoraxjnl-2015-207252 [DOI] [PubMed]; Walsh SL, Calandriello L, Sverzellati N, Wells AU, Hansell DM. UIP Observer Consort Interobserver agreement for the ATS/ERS/JRS/ALAT criteria for a UIP pattern on CT. Thorax. 2016;71(1):45–51. doi: 10.1136/thoraxjnl-2015-207252. https://doi.org/10.1136/thoraxjnl-2015-207252 [DOI] [PubMed] [Google Scholar]
  • 14.14 Sverzellati N, Wells AU, Tomassetti S, Desai SR, Copley SJ, Aziz ZA, et al. Biopsy-proved idiopathic pulmonary fibrosis: spectrum of nondiagnostic thin-section CT diagnoses. Radiology. 2010;254(3):957-64. https://doi.org/10.1148/radiol.0990898 [DOI] [PubMed]; Sverzellati N, Wells AU, Tomassetti S, Desai SR, Copley SJ, Aziz ZA. Biopsy-proved idiopathic pulmonary fibrosis spectrum of nondiagnostic thin-section CT diagnoses. Radiology. 2010;254(3):957–964. doi: 10.1148/radiol.0990898. https://doi.org/10.1148/radiol.0990898 [DOI] [PubMed] [Google Scholar]
  • 15.15 Raghu G. Idiopathic pulmonary fibrosis. A rational clinical approach. Chest. 1987;92(1):148-54. https://doi.org/10.1378/chest.92.1.148 [DOI] [PubMed]; Raghu G. Idiopathic pulmonary fibrosis A rational clinical approach. Chest. 1987;92(1):148–154. doi: 10.1378/chest.92.1.148. https://doi.org/10.1378/chest.92.1.148 [DOI] [PubMed] [Google Scholar]
  • 16.16 Misumi S, Lynch DA. Idiopathic pulmonary fibrosis/usual interstitial pneumonia: imaging diagnosis, spectrum of abnormalities, and temporal progression. Proc Am Thorac Soc. 2006;3(4):307-14. https://doi.org/10.1513/pats.200602-018TK [DOI] [PubMed]; Misumi S, Lynch DA. Idiopathic pulmonary fibrosis/usual interstitial pneumonia imaging diagnosis, spectrum of abnormalities, and temporal progression. Proc Am Thorac Soc. 2006;3(4):307–314. doi: 10.1513/pats.200602-018TK. https://doi.org/10.1513/pats.200602-018TK [DOI] [PubMed] [Google Scholar]
  • 17.17 Hutchinson JP, Fogarty AW, McKeever TM, Hubbard RB. In-Hospital Mortality after Surgical Lung Biopsy for Interstitial Lung Disease in the United States. 2000 to 2011. Am J Resp Crit Care Med. 2016;193(10);1161-7. https://doi.org/10.1164/rccm.201508-1632OC [DOI] [PubMed]; Hutchinson JP, Fogarty AW, McKeever TM, Hubbard RB. In-Hospital Mortality after Surgical Lung Biopsy for Interstitial Lung Disease in the United States. 2000 to 2011. Am J Resp Crit Care Med. 2016;193(10):1161–1167. doi: 10.1164/rccm.201508-1632OC. https://doi.org/10.1164/rccm.201508-1632OC [DOI] [PubMed] [Google Scholar]
  • 18.18 Hutchinson JP, McKeever TM, Fogarty AW, Navaratnam V, Hubbard RB. Surgical lung biopsy for the diagnosis of interstitial lung disease in England: 1997-2008. Eur Respir J. 2016;48(5):1453-1461. https://doi.org/10.1183/13993003.00378-2016 [DOI] [PubMed]; Hutchinson JP, McKeever TM, Fogarty AW, Navaratnam V, Hubbard RB. Surgical lung biopsy for the diagnosis of interstitial lung disease in England 1997-2008. Eur Respir J. 2016;48(5):1453–1461. doi: 10.1183/13993003.00378-2016. https://doi.org/10.1183/13993003.00378-2016 [DOI] [PubMed] [Google Scholar]
  • 19.19 Raghu G, Wells AU, Nicholson AG, Richeldi L, Flaherty KR, Le Maulf F, ,et al. Effect of Nintendanib in Subgroups of Idiopathic Pulmonary Fibrosis by Diagnostic Criteria. Am J Respir Crit Care Med. 2017;195(1):78-85. https://doi.org/10.1164/rccm.201602-0402OC [DOI] [PMC free article] [PubMed]; Raghu G, Wells AU, Nicholson AG, Richeldi L, Flaherty KR, Le Maulf F. Effect of Nintendanib in Subgroups of Idiopathic Pulmonary Fibrosis by Diagnostic Criteria. Am J Respir Crit Care Med. 2017;195(1):78–85. doi: 10.1164/rccm.201602-0402OC. https://doi.org/10.1164/rccm.201602-0402OC [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.20 Lee JW, Shehu E, Gjonbrataj J, Bahn YE, Rho BH, Lee MY, et al. Clinical Findings and outcomes in patients with possible usual interstitial pneumonia. Respir Med. 2015;109(4):510-6. https://doi.org/10.1016/j.rmed.2015.02.008 [DOI] [PubMed]; Lee JW, Shehu E, Gjonbrataj J, Bahn YE, Rho BH, Lee MY. Clinical Findings and outcomes in patients with possible usual interstitial pneumonia. Respir Med. 2015;109(4):510–516. doi: 10.1016/j.rmed.2015.02.008. https://doi.org/10.1016/j.rmed.2015.02.008 [DOI] [PubMed] [Google Scholar]
  • 21.21 Gruden JF, Panse PM, Gotway MB, Jensen EA, Wellnitz CV, Wesselius L. Diagnosis of Usual Interstitial Pneumonitis in the Absence of Honeycombing: Evaluation of Specific CT Criteria With Clinical Follow-Up in 38 Patients. AJR Am J Roentgenol. 2016;206(3):472-80. https://doi.org/10.2214/AJR.15.14525 [DOI] [PubMed]; Gruden JF, Panse PM, Gotway MB, Jensen EA, Wellnitz CV, Wesselius L. Diagnosis of Usual Interstitial Pneumonitis in the Absence of Honeycombing Evaluation of Specific CT Criteria With Clinical Follow-Up in 38 Patients. AJR Am J Roentgenol. 2016;206(3):472–480. doi: 10.2214/AJR.15.14525. https://doi.org/10.2214/AJR.15.14525 [DOI] [PubMed] [Google Scholar]
  • 22.22 Gruden JF, Panse PM, Leslie KO, Tazelaar HD, Colby TV. UIP diagnosed at surgical lung biopsy, 2000-2009: HRCT patterns and proposed classification system. AJR Am J Roentgenol. 2013;200(5):W458-67. https://doi.org/10.2214/AJR.12.9437 [DOI] [PubMed]; Gruden JF, Panse PM, Leslie KO, Tazelaar HD, Colby TV. UIP diagnosed at surgical lung biopsy, 2000-2009: HRCT patterns and proposed classification system. AJR Am J Roentgenol. 2013;200(5):W458–W467. doi: 10.2214/AJR.12.9437. https://doi.org/10.2214/AJR.12.9437 [DOI] [PubMed] [Google Scholar]
  • 23.23 Chung JH, Chawla A, Peljto AL, Cool CD, Groshong SD, Talbert JL, et al. CT scan findings of probable usual interstitial pneumonitis have a high predictive value for histologic usual interstitial pneumonitis. Chest. 2015;147(2):450-459. https://doi.org/10.1378/chest.14-0976 [DOI] [PMC free article] [PubMed]; Chung JH, Chawla A, Peljto AL, Cool CD, Groshong SD, Talbert JL. CT scan findings of probable usual interstitial pneumonitis have a high predictive value for histologic usual interstitial pneumonitis. Chest. 2015;147(2):450–459. doi: 10.1378/chest.14-0976. https://doi.org/10.1378/chest.14-0976 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.24 Raghu G, Lynch D, Godwin JD, Webb R, Colby TV, Leslie KO, et al. Diagnosis of idiopathic pulmonary fibrosis with high-resolution CT in patients with little or no radiological evidence of honeycombing: secondary analysis of a randomised, controlled trial. Lancet Respir Med. 2014;2(4):277-84. https://doi.org/10.1016/S2213-2600(14)70011-6 [DOI] [PubMed]; Raghu G, Lynch D, Godwin JD, Webb R, Colby TV, Leslie KO. Diagnosis of idiopathic pulmonary fibrosis with high-resolution CT in patients with little or no radiological evidence of honeycombing secondary analysis of a randomised, controlled trial. Lancet Respir Med. 2014;2(4):277–284. doi: 10.1016/S2213-2600(14)70011-6. https://doi.org/10.1016/S2213-2600(14)70011-6 [DOI] [PubMed] [Google Scholar]
  • 25.25 Brownell R, Moua T, Henry TS, Elicker BM, White D, Vittinghoff E, et al. The use of pretest probability increases the value of high-resolution CT in diagnosing usual interstitial pneumonia. Thorax. 2017;72(5):424-429. https://doi.org/10.1136/thoraxjnl-2016-209671 [DOI] [PMC free article] [PubMed]; Brownell R, Moua T, Henry TS, Elicker BM, White D, Vittinghoff E. The use of pretest probability increases the value of high-resolution CT in diagnosing usual interstitial pneumonia. Thorax. 2017;72(5):424–429. doi: 10.1136/thoraxjnl-2016-209671. https://doi.org/10.1136/thoraxjnl-2016-209671 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.26 Salisbury ML, Xia M, Murray S, Bartholmai BJ, Kazerooni EA, Meldrum CA, et al. Predictors of idiopathic pulmonary fibrosis in absence of radiologic honeycombing: A cross sectional analysis in ILD patients undergoing lung tissue sampling. Respir Med. 2016;118:88-95. https://doi.org/10.1016/j.rmed.2016.07.016 [DOI] [PMC free article] [PubMed]; Salisbury ML, Xia M, Murray S, Bartholmai BJ, Kazerooni EA, Meldrum CA. Predictors of idiopathic pulmonary fibrosis in absence of radiologic honeycombing A cross sectional analysis in ILD patients undergoing lung tissue sampling. Respir Med. 2016;118:88–95. doi: 10.1016/j.rmed.2016.07.016. https://doi.org/10.1016/j.rmed.2016.07.016 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Pereira CA, Gimenez A, Kuranishi L, Storrer K. Chronic hypersensitivity pneumonitis. J Asthma Allergy. 2016;9:171-181. eCollection 2016. [DOI] [PMC free article] [PubMed]; Pereira CA, Gimenez A, Kuranishi L, Storrer K. Chronic hypersensitivity pneumonitis. J Asthma Allergy. 2016;9:171–181. doi: 10.2147/JAA.S81540. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.28 Salisbury ML, Myers JL, Belloli EA, Kazerooni EA, Martinez FJ, Flaherty KR. Diagnosis and Treatment of Fibrotic Hypersensitivity Pneumonia. Where We Stand and Where We Need to Go. Am J Respir Crit Care Med. 2016 Dec 21. [Epub ahead of print] https://doi.org/10.1164/rccm.201608-1675PP [DOI] [PMC free article] [PubMed]; Salisbury ML, Myers JL, Belloli EA, Kazerooni EA, Martinez FJ, Flaherty KR. Diagnosis and Treatment of Fibrotic Hypersensitivity Pneumonia. Where We Stand and Where We Need to Go. Am J Respir Crit Care Med. 2016 doi: 10.1164/rccm.201608-1675PP. https://doi.org/10.1164/rccm.201608-1675PP [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.29 American Thoracic Society; European Respiratory Society. American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001. Am J Respir Crit Care Med. 2002;165(2):277-304. https://doi.org/10.1164/ajrccm.165.2.ats01 [DOI] [PubMed]; American Thoracic SocietyEuropean Respiratory Society American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001. Am J Respir Crit Care Med. 2002;165(2):277–304. doi: 10.1164/ajrccm.165.2.ats01. https://doi.org/10.1164/ajrccm.165.2.ats01 [DOI] [PubMed] [Google Scholar]
J Bras Pneumol. 2017 Sep-Oct;43(5):393–398. [Article in Portuguese]

Pneumonia intersticial usual: padrões típico, possível e inconsistente

Pedro Paulo Teixeira e Silva Torres 1, Marcelo Fouad Rabahi 2, Maria Auxiliadora Carmo Moreira 2, Gustavo de Souza Portes Meirelles 3, Edson Marchiori 4

RESUMO

A fibrose pulmonar idiopática é uma pneumopatia intersticial fibrosante crônica de curso grave e progressivo, e seu diagnóstico se dá em combinações específicas de correlações clínicas e radiológicas, ou ainda patológicas. A TCAR tem papel chave no diagnóstico morfológico do padrão de pneumonia intersticial usual (PIU), segundo as recomendações internacionais vigentes. Os níveis de certeza para a leitura do padrão tomográfico foram inseridos em diretrizes atuais, descritos como padrão PIU típico, padrão PIU possível e padrão inconsistente com PIU, cada qual com importantes implicações na cadeia diagnóstica. A presença do padrão PIU típico tem alta concordância com o padrão PIU histopatológico, e, nessa situação, a TCAR é tida como suficiente para a determinação do padrão morfológico. Nos demais padrões, investigações diagnósticas complementares são indicadas. O diagnóstico diferencial com outras entidades, incluindo pneumopatias intersticiais por exposição medicamentosa, exposições extrínsecas (pneumonite de hipersensibilidade crônica), doenças ocupacionais (asbestose) e doenças do tecido conjuntivo, deve ser considerado clinicamente. Dada a importância da abordagem tomográfica, a qual pode apresentar relevantes discordâncias na avaliação interobservador, nosso objetivo foi ilustrar os padrões tomográficos de PIU neste ensaio pictórico.

Descritores: Tomografia computadorizada por raios X, Doenças pulmonares intersticiais, Fibrose pulmonar

INTRODUÇÃO

A fibrose pulmonar idiopática (FPI) é uma pneumopatia intersticial fibrosante crônica de curso variável, usualmente progressivo. Critérios diagnósticos definidos em diretrizes recentes incluem a exclusão de potenciais causas de pneumopatias intersticiais e a definição de padrão morfológico de pneumonia intersticial usual (PIU) na TCAR ou em combinações específicas de padrões na TCAR e biópsia cirúrgica.1,2

A caracterização de padrões típicos de PIU na TCAR apresenta alta concordância com a biópsia cirúrgica em múltiplas séries (90-100%), sendo que, atualmente, um diagnóstico imagenológico confiável de padrão PIU é considerado suficiente para a confirmação desse padrão morfológico, dispensando a realização de biópsia cirúrgica.1 Em padrões tomográficos menos característicos, a correlação histopatológica estaria indicada segundo as recomendações atuais, e, nessa situação, o diagnóstico será estabelecido em combinações específicas de achados imagenológicos e histopatológicos.1 Nesse sentido, a adequada interpretação da TCAR é definitiva para a condução diagnóstica, especialmente considerando-se a aprovação recente de medicações antifibróticas, até o momento específicas para o tratamento de FPI.3

A aplicação de níveis de certeza para a definição tomográfica do padrão PIU é recomendada nas diretrizes atuais, sendo descritos três padrões: padrão PIU típico (biópsia cirúrgica não recomendada), padrão PIU possível e padrão inconsistente com PIU (esses últimos requerendo correlações histopatológicas por biópsia cirúrgica).1,2,4 O objetivo do presente estudo foi descrever e ilustrar os critérios para o enquadramento dos pacientes em cada um desses padrões.

CRITÉRIOS PARA CARACTERIZAÇÃO TOMOGRÁFICA DO PADRÃO PIU

Padrão PIU típico

O padrão PIU típico apresenta opacidades reticulares de predomínio periférico e basal, associado a faveolamento, estando presentes ou não bronquiolectasias de tração. Não devem estar presentes nenhuma das alterações descritas no padrão inconsistente com PIU (Figura 1).1 Havendo preenchimento de todos esses critérios, os achados são considerados patognomônicos para PIU, dispensando a correlação com a biópsia cirúrgica.1 Há alta concordância interobservador para o reconhecimento do padrão PIU típico entre radiologistas.5,6 É importante pontuar que o padrão morfológico PIU e FPI não são sinônimos, sendo conhecidas inúmeras causas determinando esse padrão, entre elas: exposições a drogas, doenças ocupacionais (por exemplo, asbestose), pneumonite por hipersensibilidade e doenças do tecido conjuntivo.5

Figura 1. Paciente do sexo feminino, 77 anos; padrão típico de pneumonia intersticial usual. Imagens de TC do tórax em janela de pulmão no plano axial (em A) mostrando opacidades reticulares, bronquiectasias de tração e extenso faveolamento associado, e imagens em reformatação coronal (em B) evidenciando gradiente apicobasal do acometimento.

Figura 1

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Padrão PIU possível

O padrão PIU possível apresenta opacidades reticulares de predomínio periférico e basal, sem faveolamento ou alterações descritas no padrão inconsistente com PIU (Figura 2).1 No padrão possível, a especificidade para diagnóstico de PIU é menor, e o principal diagnóstico diferencial a ser considerado é a pneumonia intersticial não específica (PINE) fibrótica.5 Ausência de faveolamento, maior extensão de padrão em vidro fosco, preservação relativa do interstício subpleural (subpleural sparing) e redução volumétrica de lobos inferiores são fatores que favorecem o diagnóstico de PINE.7-9 O faveolamento é raro na PINE, sendo observado em menos de 5% dos pacientes estudados em uma série de pacientes com PINE idiopática.7

Figura 2. Paciente do sexo masculino, 75 anos; padrão possível de pneumonia intersticial usual. Imagens de TC em janela de pulmão no plano axial (em A) e reformatação coronal (em B) mostrando opacidades reticulares e bronquiolectasias de tração de distribuição periférica (em A), com gradiente apicobasal (em B), sem definição de faveolamento.

Figura 2

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Padrão inconsistente com PIU

Dentre as características desse padrão, temos: a) doença de distribuição longitudinal nos campos pulmonares médios e superiores; b) predomínio peribroncovascular das alterações no eixo axial (Figura 3); c) padrão em vidro fosco desproporcional (maior extensão que as opacidades reticulares); d) micronódulos esparsos, bilaterais, predominando em campos pulmonares superiores (Figura 4); e) cistos (múltiplos, bilaterais, dissociados das áreas de fibrose); f) padrão de perfusão em mosaico/aprisionamento aéreo, bilateral, em mais de três lobos (Figura 5); e g) consolidações. Os achados descritos nesse padrão devem suscitar a busca por diagnóstico diferencial, vários deles remetendo a pneumonite de hipersensibilidade crônica (PHC).5

Figura 3. Paciente do sexo feminino, 38 anos; padrão inconsistente com pneumonia intersticial usual, com diagnóstico de pneumonite de hipersensibilidade crônica. Imagem de TCAR do tórax em janela de pulmão no plano axial evidenciando opacidades reticulares esparsas com bronquiolectasias de tração, destacando-se importante acometimento do feixe peribroncovascular no lobo superior direito (seta).

Figura 3

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Figura 4. Paciente do sexo feminino, 63 anos; padrão inconsistente com pneumonia intersticial usual, com diagnóstico de sarcoidose. Imagem de TCAR do tórax em janela de pulmão no plano axial evidenciando opacidades reticulares confluentes, predominantemente peribroncovasculares, porém com caracterização de micronódulos de distribuição perilinfática (setas).

Figura 4

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Figura 5. Paciente do sexo feminino, 61 anos; padrão inconsistente com pneumonia intersticial usual, com diagnóstico de pneumonite de hipersensibilidade crônica. Imagens de TCAR do tórax em janela de pulmão no plano axial evidenciando opacidades reticulares esparsas, além de áreas em vidro fosco com áreas de menor atenuação associadas (setas), caracterizando padrão em mosaico.

Figura 5

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CONSIDERAÇÕES ESPECIAIS

Aspectos técnicos

A aquisição de imagens com parâmetros satisfatórios é fundamental para o diagnóstico correto; os requisitos técnicos mínimos incluem: a) imagens adquiridas em inspiração plena, sem artefatos de movimentação; b) imagens axiais finas, sequenciais ou volumétricas, com intervalo de reconstrução ≤ 2 cm; c) espessura de corte ≤ 2 mm; d) utilização de algoritmo de alta resolução; e) campo de visão otimizado para incluir somente parênquima pulmonar; f) aquisições expiratórias são úteis para definição de aprisionamento aéreo; g) utilização de decúbito ventral em caso de dúvida com opacidades decúbito-dependentes; e h) utilização de reconstruções multiplanares no caso de aquisição volumétrica.10

Manobras inspiratórias inadequadas podem determinar aumento/heterogeneidade na atenuação pulmonar e gerar artefatos de movimentação que podem determinar um potencial prejuízo na avaliação do estudo (Figura 6). Sugestões para a melhora na técnica do estudo incluem utilizar orientações simples e diretas quanto às manobras inspiratórias/expiratórias; realizar treinamento dos níveis respiratórios antes da aquisição definitiva; e inserir períodos de repouso durante aquisições sequenciais.10

Figura 6. Imagens axiais de TC do tórax em janela de pulmão. Em A, primeira aquisição realizada com nível inspiratório subótimo simulando presença de vidro fosco difuso e, em B, avaliação após reconvocação e nova aquisição com parâmetros inspiratórios adequados.

Figura 6

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Diagnóstico de faveolamento

A correta percepção tomográfica de faveolamento é um passo crucial na definição de padrão PIU típico e diagnóstico clinicoimagenológico de FPI.1 Entretanto, mesmo entre examinadores com alta experiência em doença intersticial pulmonar, há relevante variabilidade interobservador tanto na detecção quanto na diferenciação de outros padrões, como bronquiectasias de tração, doença cística e superposição com enfisema pulmonar (Figura 7).11 Critérios para diagnóstico de faveolamento devem ser aplicados e são definidos como: a) cistos entre 3-10 mm agrupados, compartilhando paredes relativamente espessas (1-3 mm); e b) disposição em camadas usualmente em situação subpleural, assegurando-se de que não há definição de enfisema.11,12

Figura 7. Imagem axial de TCAR em janela pulmonar (em A) e reformatação em projeção de intensidade mínima (em B). Em A, caracterizam-se imagens císticas agrupadas em situação subpleural suspeitas para faveolamento (setas), que se confirmaram somente como bronquiectasias de tração na reformatação coronal oblíqua em B (setas).

Figura 7

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Concordância interobservador: critérios tomográficos para padrões PIU

Walsh et al.13 avaliaram a variabilidade interobservador para a aplicação dos critérios para definição do padrão tomográfico PIU. A concordância entre os critérios para esse padrão foi apenas moderada, tanto para radiologistas gerais quanto para radiologistas torácicos experientes no tipo de amostra examinada, sendo que a heterogeneidade na caracterização de faveolamento foi atribuída como possível fonte de dificuldade na distinção desses padrões.

Padrões atípicos e diagnóstico diferencial

Embora um aspecto tomográfico típico possa predizer o diagnóstico histopatológico de PIU, achados característicos podem estar ausentes em até 30% dos pacientes.14 Sverzellati et al.14 estudaram casos de PIU confirmados histopatologicamente e demonstraram que, em 62% dos casos, os radiologistas sugeriram diagnósticos alternativos. Aquele estudo14 ilustra que, embora a tomografia tenha alta acurácia para o diagnóstico de padrão PIU em situações típicas, o estudo tomográfico não deve ser utilizado para afastar essa possibilidade. Em casos atípicos, radiologistas mais frequentemente sugerem diagnósticos de PINE, PHC, sarcoidose e pneumonia em organização crônica.

Evolução temporal

O curso clínico da FPI é variável e imprevisível no momento do diagnóstico: enquanto a maioria dos pacientes apresenta piora lenta e progressiva ao longo dos anos, há aqueles que permanecem estáveis, e outros que evoluem com rápida piora.1,15 Com a acentuação dos achados na TCAR, áreas de vidro fosco usualmente progridem para opacidades reticulares e essas, por sua vez, para faveolamento, que aumenta em extensão e tamanho ao longo do tempo.16 Deve-se ressaltar que a interpretação tomográfica é dinâmica, e, em pacientes com curso progressivo, é possível que resultados de TC inicialmente diagnosticados como padrão PIU possível evoluam temporalmente para padrão PIU típico (Figura 8).

Figura 8. Imagens axiais de TCAR do tórax em janela pulmonar evidenciando o lobo inferior direito. Em A, exame inicial preenchendo critérios padrão possível com pneumonia intersticial usual (PIU), com opacidades reticulares e vidro fosco, sem faveolamento. Em B, estudo de controle após seis anos evidenciando a progressão dos achados e o surgimento de faveolamento, preenchendo, então, os critérios para padrão PIU típico.

Figura 8

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Direções futuras

Riscos referentes à biópsia cirúrgica em doenças intersticiais devem ser considerados, sendo frequentes situações em que a biópsia é contraindicada pelo quadro clínico do paciente, determinando prejuízos na condução diagnóstica e tratamento.17,18 Nesse sentido, há um crescente interesse da literatura a respeito do diagnóstico não invasivo de FPI, especialmente considerando-se pacientes com padrão tomográfico PIU possível. Estudos recentes comparando pacientes portadores de FPI com padrão tomográfico PIU típico e PIU possível têm demonstrado semelhanças entre o comportamento clínico e funcional de ambos, e, ainda, evidências de resposta comparáveis no tratamento antifibrótico com nintendanibe nesses subgrupos.19-21 Tem sido descrito ainda uma alta frequência de confirmação histopatológica de PIU em pacientes com padrão tomográfico PIU possível em diversas séries de pacientes com FPI.22-25 A idade de início da doença e a extensão da fibrose no estudo inicial têm sido significativamente relacionados a alta probabilidade de diagnóstico de FPI, sendo sugerida a possibilidade de diagnóstico clinicorradiológico no padrão PIU possível se: a) a apresentação clínica e demográfica definida por um especialista em doença intersticial for típica (paciente com mais de 60 anos, apresentando dispneia aos esforços e fibrose pulmonar de etiologia indeterminada); e b) especialista em imagem intersticial definindo o padrão PIU possível.24,26

É importante considerar que, dentre os estudos sugerindo que o padrão tomográfico PIU possível seja suficiente para o diagnóstico de FPI, alguns derivam de ensaios clínicos com alta prevalência de FPI, o que pode haver superestimado esses resultados.23,24 O estudo de Brownell et al.25 demonstra que o padrão PIU possível tem alta especificidade para padrão PIU na biópsia; porém, o valor preditivo positivo desse padrão está diretamente relacionado à frequência de FPI na população em estudo. Nesse sentido, em populações com baixa frequência ou frequência indeterminada de FPI, os autores sugerem que seria inadequado assumir o padrão tomográfico PIU possível como confirmatório de padrão PIU histopatológico.25. Como no Brasil a PHC tem alta prevalência (até 15%), estudos são necessários para determinar qual é a frequência de FPI dentro do padrão PIU possível antes que se exclua a necessidade de biópsia nesse grupo.27

Sugestões de algoritmos diagnósticos não invasivos também têm sido publicadas para PHC, envolvendo apresentação tomográfica típica, linfocitose no lavado broncoalveolar (> 20-30% na contagem de linfócitos) e identificação de nexo causal, sendo de grande valia na abordagem diagnóstica das doenças intersticiais fibróticas, considerando-se que, frequentemente, é difícil o diagnóstico diferencial entre PHC e FPI.27,28

CONSIDERAÇÕES FINAIS

A FPI é a mais frequente entre as pneumopatias intersticiais idiopáticas, com grave prognóstico na maioria dos casos, cujo substrato histopatológico é a PIU.29 Uma revisão recente do algoritmo diagnóstico dessa entidade reforça o papel da TCAR como método indispensável na definição do padrão morfológico de PIU em quadros característicos ou na sinalização da necessidade de correlação histopatológica em quadros menos típicos.1 O conhecimento e a aplicação desses padrões por parte do radiologista nos relatórios imagenológicos ou em reuniões multidisciplinares é fundamental para a condução diagnóstica, especialmente considerando-se as perspectivas atuais de tratamento com drogas antifibróticas para FPI.

1

Trabalho realizado em Multimagem Diagnósticos e na Universidade Federal de Goiás, Goiânia (GO) Brasil.

Apoio financeiro: Nenhum.

Articles from Jornal Brasileiro de Pneumologia are provided here courtesy of Sociedade Brasileira de Pneumologia e Tisiologia (Brazilian Thoracic Society)

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