9
J Korean Radiol Soc 2007;57:441-449 441 Assessment of Subpleural Opacities on High-Resolution CT 1 Hee Seok Choi, M.D., Jeung Sook Kim, M.D., Eun-Young Kang, M.D. 2 , Hak Hee Kim, M.D. 3 1 Department of Radiology, Dongguk University International Hospital 2 Department of Radiology, Korea University Guro Hospital 3 Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine Received July 1, 2007 ; Accepted September 17, 2007 Address reprint requests to : Jeung Sook Kim, M.D., PhD, Department of Radiology, Dongguk University International Hospital, 814 Siksa-dong, Ilsandong-gu, Goyang-si, Gyeonggi-do 410-773, Korea Tel. 82-31-961-7823 Fax. 82-31-961-8802 E-mail: [email protected], [email protected] Purpose: The purpose of this study was to assess the value of HRCT for determining the cause of subpleural opacities. Materials and Methods: We evaluated 49 cases of subpleural opacities on HRCT scan, among with the patients with subpleural opacities seen on the conventional chest radi- ographs. Two “blinded” reviewers retrospectively analyzed the CT scans by working in consensus. Results: The patients consisted of COP ( n=14), NSIP ( n=13), UIP ( n =10), fibrosis as- sociated with connective tissue disease or drug toxicity (n=4), CEP (n=4), Churg- Strauss syndrome ( n=2), DIP ( n=1) and AIP ( n=1). The predominant findings were consolidation (57%) with a peribronchovascular distribution (57%) in the COP pa- tients, GGO (69%) and the associated focal reticular densities (61%) in the NSIP pa- tients, and reticular or reticulonodular densities with a paucity of GGO in the UIP pa- tients (100%). For the diagnosis of COP, NSIP and UIP, the use of HRCT demonstrated a high sensitivity (86%, 85% and 90%, respectively), specificity (97%, 86% and 95%) and accuracy (94%, 86% and 94%). Conclusion: Although an overlap of CT findings is seen for diseases showing subpleur- al opacities, consolidation with a subpleural and peribronchovascular distribution is highly suggestive for COP, subpleural GGO is highly suggestive of NSIP, subpleural reticular or reticulonodular densities with a paucity of GGO is highly suggestive of UIP, and subpleural consolidation accompanied by reticular densities is suggestive of fibrosis. Index words : Tomography, X- ray computed Lung diseases, interstitial Pneumonia

Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

  • Upload
    hatuyen

  • View
    220

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

J Korean Radiol Soc 2007;57:441-449

─ 441 ─

Assessment of Subpleural Opacities on High-Resolution CT1

Hee Seok Choi, M.D., Jeung Sook Kim, M.D., Eun-Young Kang, M.D.2, Hak Hee Kim, M.D.3

1Department of Radiology, Dongguk University International Hospital2Department of Radiology, Korea University Guro Hospital3Department of Radiology, Asan Medical Center, University of Ulsan College of MedicineReceived July 1, 2007 ; Accepted September 17, 2007Address reprint requests to : Jeung Sook Kim, M.D., PhD, Department of Radiology, Dongguk University International Hospital, 814 Siksa-dong, Ilsandong-gu, Goyang-si, Gyeonggi-do 410-773, KoreaTel. 82-31-961-7823 Fax. 82-31-961-8802E-mail: [email protected], [email protected]

Purpose: The purpose of this study was to assess the value of HRCT for determiningthe cause of subpleural opacities.Materials and Methods: We evaluated 49 cases of subpleural opacities on HRCT scan,among with the patients with subpleural opacities seen on the conventional chest radi-ographs. Two “blinded” reviewers retrospectively analyzed the CT scans by working inconsensus.Results: The patients consisted of COP (n=14), NSIP (n=13), UIP (n =10), fibrosis as-sociated with connective tissue disease or drug toxicity (n=4), CEP (n=4), Churg-Strauss syndrome (n=2), DIP (n=1) and AIP (n=1). The predominant findings wereconsolidation (57%) with a peribronchovascular distribution (57%) in the COP pa-tients, GGO (69%) and the associated focal reticular densities (61%) in the NSIP pa-tients, and reticular or reticulonodular densities with a paucity of GGO in the UIP pa-tients (100%). For the diagnosis of COP, NSIP and UIP, the use of HRCT demonstrateda high sensitivity (86%, 85% and 90%, respectively), specificity (97%, 86% and 95%)and accuracy (94%, 86% and 94%).Conclusion: Although an overlap of CT findings is seen for diseases showing subpleur-al opacities, consolidation with a subpleural and peribronchovascular distribution ishighly suggestive for COP, subpleural GGO is highly suggestive of NSIP, subpleuralreticular or reticulonodular densities with a paucity of GGO is highly suggestive ofUIP, and subpleural consolidation accompanied by reticular densities is suggestive offibrosis.

Index words : Tomography, X- ray computedLung diseases, interstitialPneumonia

Page 2: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

Many interstitial lung diseases show a specific region-al distribution or a predilection site that is related to theunderlying pathogenesis and pathophysiology (1). Thediagnosis or differential diagnosis of lung disease using ahigh-resolution CT (HRCT) requires consideration of thedistribution of pulmonary abnormalities, along with ex-amining these pulmonary abnormalities on HRCT. Aperipheral or subpleural predominance of abnormalitiesis usually found in the outer third of the lung and this issuggestive of a number of diseases such as eosinophilicpneumonia, usual interstitial pneumonia (UIP), crypto-genic organizing pneumonia (COP, formerly bronchioli-tis obliterans organizing pneumonia), nonspecific inter-stitial pneumonia (NSIP), desquamative interstitialpneumonia (DIP), acute interstitial pneumonia (AIP),hematogenous metastases, hypersensitivity pneumoni-tis and asbestosis (1, 2).

The purpose of this study was to evaluate whether aspecific pattern, distribution and associated findings ofsubpleural opacities on HRCT can be used to differenti-ate the lung diseases that are responsible for subpleuralopacities.

Materials and Methods

We retrospectively reviewed the conventional chestradiographs that were taken between May 2000 andDecember 2005 and collected cases that had subpleuralopacities seen on conventional chest radiographs.Among these cases, we included the patients who hadsubpleural opacities on their HRCT scan. Patients withpulmonary or extrapulmonary documented infection ormalignancy were excluded from the study. The includ-ed cases were limited to patients who were diagnosedwith interstitial lung disease.

The resulting study population consisted of 49 patients(21 men and 28 women) with an age range of 19-81years (mean age: 55 years). The diagnosis was based onopen lung biopsy (n=24), transbronchial lung biopsy (n=10), percutaneous needle biopsy (n=1), and a combi-nation of laboratory results that included bronchoalveo-lar lavage and blood eosinophilia, as well as the clinicalfindings and response to treatment (n=14). The meantime interval between the HRCT scanning and biopsywas 12 days. Seven patients were diagnosed with UIPwithout examining the pathological findings. These sev-en patients were diagnosed with UIP by the AmericanThoracic Society criteria for the diagnosis of IPF (idio-pathic pulmonary fibrosis) in the absence of a surgical

biopsy (3). The other seven clinically diagnosed caseswere COP (n=1), NSIP (n=1), fibrosis (n=2), CEP (n=1)and Churg-Strauss syndrome (n=2).

All the patients underwent HRCT of the chest on aSomatom Plus 40, a Somatom Plus 32 or a SomatomSensation 64 (Siemens, Erlangen, Germany). The HRCTscans were obtained with 1-mm collimation at 7-mm or10-mm intervals. The HRCT images were reconstructedwith a high-spatial-frequency algorithm. The CT scanswere obtained with the patients at suspended end-inspi-ratory effort; the patients were in the supine positionand scanning was done without intravenous contrastmaterial. Additional CT scans were performed at endexpiration. All the images were viewed at window lev-els that were appropriate for examining the lungparenchyma (window width: 1,500 ~ 1,700 HU, win-dow level: -600 ~ -700 HU) and mediastinum (win-dow width: 450 ~ 500 HU, window level: 35 ~ 50 HU).

Two radiologists who were unaware of the clinicaland pathologic data of the patients retrospectively ana-lyzed the CT scans. They knew only the age and genderof the patients. The final diagnostic decision wasreached by consensus. The two radiologists analyzedthe presence and extent of consolidation, the ground-glass opacities (GGOs), the nodular densities, the reticu-lar densities, the reticulonodular densities and thebronchiectasis of each case. They decided on the pre-dominant finding and the distribution of each of thefindings. Other associated findings such as lym-phadenopathy, air-trapping and pleural effusion werealso analyzed. Each abnormality and the associated find-ings were defined by consensus. Areas with GGO weredefined as areas with hazy increased attenuation with-out obscuration of the underlying vascular markings.Consolidation was considered present when the opaci-ties obscured the underlying vessels. A nodule was de-fined as a focal, rounded opacity of varying size that waswell defined or not well defined. Reticular densitieswere defined as fine linear opacities that were arrangedin an irregular net-like pattern, and reticulonodular den-sities were defined as a mixture of nodular and reticularpatterns. Honeycombing was defined as clustered cysticairspaces that shared walls and this occurred in severallayers at the pleural surfaces. Bronchiectasis was consid-ered present when the internal diameter of a bronchuswas greater than the diameter of the adjacent pul-monary arteries and there was a loss of normal taperingof the bronchial lumen.

The distribution of each finding into the upper, middle

Hee Seok Choi, et al : Assessment of Subpleural Opacities on High-Resolution CT

─ 442 ─

Page 3: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

and lower lung zones, as well as into the central and pe-ripheral zones, the bronchovascular bundle and the ran-dom distributions, were analyzed. The cross-anatomicdistribution was evaluated according to the following: aperipheral or subpleural predominance of abnormalitieswas seen in the outer third of the lung, a central pre-dominance of abnormalities was seen in the inner thirdof the lung, and a peribronchial predominance of abnor-malities occurred along the bronchovascular bundle.The cross-sectional distribution was defined to be ran-dom if a predominant pattern was not observed. The ax-ial anatomic distribution was evaluated according to thefollowing: the upper lung zone was above the level ofthe aortic arch, the middle lung zone was between thelevel of the aortic arch and the level of the right inferiorpulmonary vein, and the lower lung zone was below theright inferior pulmonary vein. The axial distributionwas defined to be the whole lung zones if a predominantzone was not observed.

The fibrosis of the lung parenchyma was defined asdestruction of the architecture of the secondary pul-monary lobules that resulted in consolidation or reticu-lar densities on the HRCT. Cases with focal fibrosis ac-companied by other interstitial lung disease were not in-

cluded in the diagnosis of fibrosis.The sensitivity, specificity, accuracy, positive predic-

tive value and negative predictive value for the diagno-sis of COP, NSIP and UIP were evaluated. For other dis-eases, the number of patients was too small to performstatistical analysis.

Results

The patients with predominant subpleural opacitiesseen on HRCT were diagnosed with COP (n=14), NSIP(n=13), UIP (n=10), fibrosis (n=4), chronic eosinophilicpneumonia (CEP) (n=4), Churg-Strauss syndrome(n=2), AIP (n=1) and DIP (n=1). The HRCT findingsand their distributions for each disease are listed in ta-bles 1 and 2.

For patients with COP (n=14), the predominant find-ing was consolidation (n=8, 57%). Other predominantfindings were GGO (n=4), reticular densities (n=1) andnodular densities (n=1). Other associated findings werebronchiectasis (n= 3), mediastinal lymphadenopathy (n=1) and air trapping (n=1). The distribution of the opac-ities in COP patients was predominantly along the bron-chovascular bundle (n=8, 57%) (Fig. 1). However, for

J Korean Radiol Soc 2007;57:441-449

─ 443 ─

Table 1. HRCT Findings of Each Disease with Subpleural Opacities

Disease Predominant findings Associated findings

(No. Consolidation GGO Reticular or Nodular Associated Honey- Bronchiectasis Lymph-of cases) Reticulonodular D D Reticular D combing adenopathy

COP (14) 8 4 01 01 1 10 03 1NSIP (13) 0 9 04 04 0 08 10 5UIP (10) 0 0 10 10 0 - 06 6Fibrosis (4) 3 0 01 01 0 03 03 0CEP (4) 2 2 00 00 0 03 01 0Churg-Strauss SD (2) 0 2 00 00 0 00 00 0AIP (1) 0 1 00 00 0 00 00 0DIP (1) 0 1 00 00 0 01 00 0

GGO: ground-glass opacity, D: Densities, SD: syndrome

Table 2. Distribution of Subpleural Opacities on HRCT

Disease Cross distribution Axial distribution

(No. of cases) Subpleural Central Random Bronchovascular Whole ML L U

COP (14) 13 0 1 8 07 4 3 0NSIP (13) 13 0 0 3 10 3 0 0UIP (10) 10 0 0 0 05 2 3 0Fibrosis (4) 04 0 0 0 03 1 0 0CEP (4) 04 0 0 0 02 2 0 0Churg-Strauss SD (2) 02 0 0 1 01 0 0 1AIP (1) 00 0 1 0 01 0 0 0DIP (1) 01 0 0 0 00 1 0 0

Whole: whole lung zones, U: upper, M: middle, L: lower, SD: syndrome

Page 4: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

the other disease entities, we could not find a specificdistribution of abnormalities along the bronchovascularbundle. The opacities identified in COP patients weremainly distributed in the peripheral or subpleural region(n=13, 92%). These opacities were distributed in the

whole lung zones (n=7), middle and lower lung zone (n=4), and lower lung zone (n=3). The cause of disease inten cases was idiopathic and the cause in four cases wascollagen vascular disease: systemic lupus erythematosus(SLE) (n=2), rheumatoid arthritis (n=1) and polymyosi-tis (n=1). The sensitivity for the diagnosis of COP was86%, the specificity was 97% and the accuracy was94%. The positive predictive value was 92% and thenegative predictive value was 94% (Table 3).

The predominant findings of patients with NSIP(n=13) were GGO (n=9, 69%) and reticular densities(n= 4). Focal reticular densities were frequently associ-ated with GGO (n=8, 61%) (Fig. 2). Mild reticular densi-ties were associated with focal GGO in the patients withDIP and COP, but we did not identify reticular densitiesassociated with the predominant GGO pattern for otherdiseases. Bronchiectasis was frequently noted (n=10).Mediastinal lymphadenopathy (n=5) and air trapping(n=1) were also noted. GGO and reticular densitieswere distributed in the peripheral or subpleural regionsin all cases. Distributions were also noted in the wholelung zones (n=10) and the middle and lower zones

Hee Seok Choi, et al : Assessment of Subpleural Opacities on High-Resolution CT

─ 444 ─

A BFig. 2. A 49-year-old woman with nonspecific interstitial pneumonia, and this was confirmed by open lung biopsy. A. High-resolution CT scans shows multifocal patchy ground-glass opacity that was mainly distributed in the subpleural region.Reticular densities and mild bronchiectasis within the ground-glass opacity are also noted. B. High-resolution CT scans obtained at the level of the liver dome reveals ground-glass opacity with focal reticular densities at thelung bases.

Fig. 1. A 47-year-old woman with cryptogenic organizingpneumonia, and this was confirmed by open lung biopsy.High-resolution CT scans shows patchy consolidation andGGO. This is distributed in the subpleural region and alongperibronchovascular bundle.

Table 3. Statistics for the Diagnosis of COP, NSIP and UIP on HRCT

Disease (No. of cases) Sensitivity (%) Specificity (%) Accuracy (%) PPV (%) NPV (%)

COP (14) 86 97 94 92 94 NSIP (13) 85 86 86 69 94 UIP (10) 90 95 94 82 97

PPV: positive predictive value, NPV: negative predictive value

Page 5: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

(n=3). The sensitivity for the diagnosis of NSIP was85%, the specificity was 86% and the accuracy was86%. The positive predictive value was 69% and thenegative predictive value was 94% (Table 3).

Reticular densities and reticulonodular densities werethe predominant findings of patients with UIP (n=10,100%). GGO was frequently present (n=9, 90%), butthis was less predominant and it was seen to a lesser ex-tent than reticular densities (Fig. 3). Honeycombing wasnoted in all cases, but it was not a predominant finding.Mediastinal lymphadenopathy (n=6) and bronchiectasis(n=6) were frequently noted. The distributions of reticu-lar densities were noted in peripheral regions in all cas-es. Reticular densities were noted in the whole lungzones (n=5), the middle and lower zones (n=2) and the

lower zone (n=3). The sensitivity for the diagnosis ofUIP was 90%, the specificity was 95% and the accuracywas 94%. The positive predictive value was 82% andnegative predictive value was 97% (Table 3).

For patients with fibrosis (n=4), consolidation was apredominant finding (n=3, 75%). Reticular densities asan associated finding were observed in all cases of fibro-sis (Fig. 4). There was no or only a small extent of reticu-lar densities associated with consolidation in the pa-tients with other diseases. Bronchiectasis was frequent-ly noted (n=3). There was no case with lymphadenopa-thy or air trapping. For the patients with fibrosis, consol-idation was mainly distributed in the peripheral region(n=4) and the whole lung zones (n=3). The causes of fi-brosis were SLE, scleroderma, polymyositis andbleomycin toxicity. Because we carefully excluded casesof infection as previously mentioned, the resulting caus-es of fibrosis were connective tissue diseases or drug re-actions.

For patients with CEP (n=4), consolidation (n=2,50%) and GGO (n=2, 50%) were the predominant find-ings (Fig. 5). There was no case with lymphadenopathyor air trapping. The opacities of CEP were distributed atthe peripheral region in all cases (n=4). Bronchiectasiswas infrequently seen (n=1). Consolidation and GGOmainly involved the whole lung zones (n=2) and themiddle and lower lung zones (n=2).

GGO was the predominant finding of Churg-Strausssyndrome (n=2, 100%), although there was only a smallnumber of such cases. Another associated finding of

J Korean Radiol Soc 2007;57:441-449

─ 445 ─

Fig. 3. A 63-year-old man with usual interstitial pneumonia,and this was confirmed by open lung biopsy. High-resolutionCT scans reveals bilateral subpleural reticular densities andhoneycombing with focal areas of ground-glass opacity.

Fig. 4. A 59-year-old woman with bleomycin induced fibrosis,and this was confirmed by transbronchial lung biopsy. High-resolution CT scans shows subpleural consolidation with someirregular reticular densities.

Fig. 5. A 53-year-old man with chronic eosinophilic pneumo-nia, and this was confirmed by open lung biopsy. Laboratoryexamination showed eosinophilia (66% on the CBC differen-tial count) and an increased serum IgE level. High-resolutionCT scans shows subpleural ground-glass opacity at the rightlower lobe. There is no distinct reticular density.

Page 6: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

Churg-Strauss syndrome was consolidation, but thiswas seen to a lesser extent than for GGO. There wasone case with air trapping in about 40 percent of thelung parenchyma, and this was likely a manifestation ofunderlying asthma. In addition, a subpleural predomi-nance (n=2) and peribronchovascular distribution (n=1)were also noted. GGO was distributed in the whole lungzones (n=1) and upper lung zone (n=1).

GGO was a predominant finding of AIP, and consoli-dation was also noted to a lesser extent. GGO and con-solidation were distributed in the whole lung zones.

GGO was the predominant finding of DIP.Consolidation or reticular density was not observed.GGO was distributed in the middle and lower lungzones with a subpleural distribution.

Discussion

Many interstitial lung diseases show specific regionaldistributions and predilection sites. When making thediagnosis, the distribution of pulmonary abnormalitiesshould be considered along with these abnormalities asseen on HRCT (1, 2). The diagnoses of our cases wereCOP, NSIP, UIP, CEP, fibrosis, Churg-Strauss syn-drome, AIP and DIP, which were all consistent with dis-eases showing a peripheral and subpleural predomi-nance of abnormalities, as was previously reported (1,2).

Epler et al. (4) first described COP, which was initiallydescribed as BOOP, in 1985. It was clinically character-ized as a subacute or chronic respiratory illness alongwith nonproductive cough and dyspnea. The pathologyshowed a polypoid mass of granulation tissue in the lu-mina of the small airways, the alveolar ducts and somealveoli, and this was associated with interstitial and air-space infiltration by mononuclear cells and foamymacrophages (5). The most common finding of COP onCT scans is bilateral areas of consolidation that mainlyinvolve the subpleural and/or peribronchovascular re-gions. Other findings are GGO, small nodular opacitiesor masses, and bronchial wall thickening and dilation(5-8). Some unusual CT findings in patients with COPhave been described. Linear opacities, ring-shaped opac-ities and opacity of a perilobular pattern, that is, a poorlydefined arcade-like appearance or a polygonal appear-ance are unusual CT findings (9-11). In our study, therewas no case of COP with these unusual CT findings,and this was probably due to limiting inclusion of casesto only those with subpleural opacities.

Although COP and CEP have overlapping characteris-tics, differentiation is important before initiating thera-py. The dosage and duration of corticosteroid treatmentdiffers for these two diseases (5). CEP is also associatedwith consolidation or GGO as the main finding. Themost important findings for differentiating COP fromCEP are the presence or absence of a nodule or a mass,and this is followed by nonseptal linear or reticularopacities, which are more common in COP. The pres-ence or absence of bronchiectasis and septal line thick-ening may be other discriminating findings on HRCT(5-7). In our study, the main differential finding wasthe peribronchovascular distribution of abnormalities inpatients with COP (n=8), which was not found in pa-tients with CEP or other diseases. There were COP cas-es showing nodule (n=1) and reticular densities (n=1) asthe predominant finding. Reticular densities as associat-ed findings were noted to a small extent in the COP pa-tients (n=10) and CEP patients (n=3). Bronchiectasiswas noted in the COP (n=3) and CEP patients (n=1).The presence of nodules, reticular opacities andbronchiectasis were not discriminative findings in ourstudy.

Katzenstein and Fiorelli (12) first described NSIP in1994. NSIP was proposed as the diagnosis for thosespecimens with findings that were not consistent withthe typical findings of UIP, DIP, AIP or COP. A goodprognosis was observed on the follow-up examinationsof patients with NSIP. For the NSIP patients, theirHRCT images show predominantly bilateral patchy sub-pleural areas of GGO with or without irregular linearopacities with the absence of or with a minimal extentof honeycombing. Areas of GGO in NSIP patientspathologically correspond to areas of interstitial thicken-ing that’s caused by various degrees of interstitial in-flammation or fibrosis. When irregular linear opacitiesor bronchiectasis was present within the areas of GGO,then the pathologic specimens had a tendency to showinterstitial fibrosis rather than inflammation. Because ofits different prognosis and treatment strategies, NSIPshould be differentiated from UIP and the other intersti-tial lung diseases. NSIP is pathologically differentiatedfrom UIP by the temporal and spatial homogeneity seenin NSIP. NSIP is associated with a finer reticular patternand a higher proportion of GGO on the CT scanningthan is UIP. NSIP is infrequently associated with sub-pleural honeycombing, which is seen in up to 95% ofpatients with UIP (13-16). In our study, GGO was thepredominant finding of NSIP (n=9, 69%) and focal retic-

Hee Seok Choi, et al : Assessment of Subpleural Opacities on High-Resolution CT

─ 446 ─

Page 7: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

ular densities were associated with GGO (n=8, 61%) inpatients with NSIP. GGO was not a predominant find-ing of UIP and this was only observed to a small extent.

Leibow and Carrington (17) first described UIP. UIP isgenerally found in association with connective tissuedisease, drug reactions, viral pneumonia or as a familialdisorder; yet many cases are idiopathic (also called idio-pathic pulmonary fibrosis). Histologically, the disease ischaracterized by dense fibrosis that causes remodelingof the lung architecture. There are frequent honeycombchanges, fibroblastic foci that are typically scattered atthe edges of dense scars and temporal heterogeneity(18). Clinically, UIP is characterized by a gradual onsetof dyspnea with a nonproductive cough. The prognosisis poor, with a 2.5-3.5-year median length of survivalfrom the time of diagnosis (16, 18). On HRCT, the diag-nosis of UIP is based on the presence of bilateral, pre-dominantly subpleural and basal reticular opacities withassociated traction bronchiectasis and bronchiolectasis,and honeycombing in the absence of small nodules orextensive GGO. Extensive bilateral GGO in patientswith interstitial fibrosis favors the diagnosis of NSIP orCEP over UIP (18-20). In our study, reticular or reticu-lonodular densities with a paucity of GGO were the pre-dominant findings in UIP patients. Bronchiectasis wasfrequently noted in the UIP cases (n=6, 60%) and NSIPcases (n=10, 77%). Mediastinal lymphadenopathy wasfrequently noted in the cases with UIP (n=6, 60%) andNSIP (n=5, 38%). Lymphadenopathy was not noted forthe other disease entities (except for one case of COP).

Pulmonary fibrosis is caused by a variety of diseases.For example, patients with polymyositis and dermato-myositis display consolidation with a patchy and sub-pleural distribution, thick band-like opacities and irregu-lar peribronchovascular thickening as the characteristicCT findings (21). In a previous report, interlobular septaland intralobular interstitial thickening combined witharchitectural distortion that resulted in tractionbronchiectasis and pleural irregularities were the mainfindings of SLE patients. These findings were predomi-nantly in the subpleural areas. It has been suggested thatthese findings are not specific for SLE, but they are theabnormalities noted as chronic interstitial pneumonitisin virtually all forms of connective tissue disorders (22).Pulmonary fibrosis caused by various diseases must beadded to the differential diagnosis of cases with sub-pleural opacities seen on HRCT. In our study, the caus-es of fibrosis were SLE, scleroderma, polymyositis andbleomycin toxicity. Consolidation was the predominant

finding of fibrosis (n=3, 75%). Reticular densities as anassociated finding were seen in all the cases of fibrosis.Bronchiectasis was also frequently noted (n=3, 75%).

Carrington et al. (23) first described CEP in 1969. Thisdisease was clinically characterized by a chronic illnesswith cough, fever, night sweats, weight loss and dysp-nea. Patients improve promptly when they receive cor-ticosteroid treatment. The main histologic feature ofCEP is massive infiltration of eosinophils and lympho-cytes into the alveoli and in the interstitium, with athickened alveolar wall. Approximately 50% of CEP pa-tients have a history of bronchial asthma (5). The char-acteristic CT findings are airspace consolidation and ar-eas of GGO that predominantly involve the peripheralregions of the middle or upper lung zones (24, 25). Inour study, GGO or consolidation in the subpleural areaswas the predominant finding of CEP. There was no mid-dle or upper lung zone predominance.

Churg and Strauss (26) originally described Churg-Strauss syndrome as allergic angiitis and granulomatosisin 1951. Churg-Strauss syndrome is a very rare systemicdisease that’s characterized by systemic vasculitis, ex-travascular granulomas and eosinophilia. It almost al-ways occurs in patients with asthma or a history of aller-gy. The predilection sites of involvement are the lungs,skin and nervous system. The most common HRCTfindings include subpleural consolidation or GGO witha lobular distribution, centrilobular nodules, bronchialwall thickening and an increased vessel caliber. Theconsolidation or GGO proved to be mainly hemorrhagicnecrosis. The peripheral location and lobular distribu-tion of the consolidation implies that the lesion is due toa vasculitis that involves the small and medium sized ar-teries. Along with the increased vessel caliber of the pe-ripheral small arterioles with perivascular opacities, thecentrilobular nodules reflect pulmonary vasculitis andperivascular cellular infiltration (27, 28). GGO was thepredominant finding of Churg-Strauss syndrome in ourstudy, although there were only a small number of suchcases. A bronchovascular distribution and prominent airtrapping were noted in one case; they were thought tobe perivascular and centrilobular distributions of the le-sion.

Differentiation of Churg-Strauss syndrome from CEPis necessary for the patients with hypereosinophilia andpulmonary abnormalities. The CT findings of CEP arecharacterized by the presence of homogeneous periph-eral airspace consolidation, and this responds promptlyto corticosteroid therapy, whereas peripheral consolida-

J Korean Radiol Soc 2007;57:441-449

─ 447 ─

Page 8: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

tion in Churg-Strauss syndrome has a tendency towarda lobular distribution and a frequent association of cen-trilobular nodules within the GGO. Although they arenot specific, the HRCT findings, including bronchialwall thickening in a patient with hypereosinophilia, anda history of asthma should raise the possibility of Churg-Strauss syndrome; the diagnosis would be supported bythe associated skin abnormalities (28).

The statistical results, including the sensitivity, speci-ficity, accuracy and the positive predictive value, for thediagnosis of COP, NSIP and UIP on HRCT were higherthan the data from the previous studies (3, 20, 29). Thismay be explained by the fact that our study was limitedto cases with subpleural opacities. The relatively lowerpositive predictive value (69%) for NSIP was similar tothe result of a previous study (20). The five cases show-ing predominant GGO in patients with COP, UIP andCEP were misdiagnosed as NSIP in our study.

The limitations of this study included the following.The number of patients for each diagnosis might havebeen too small to allow confident differentiation or cor-relation of results. Pathologic confirmation was notavailable for 14 patients. Seven patients were diagnosedwith UIP by the American Thoracic Society criteria forthe diagnosis of IPF (idiopathic pulmonary fibrosis) inthe absence of a surgical biopsy; further, pathologicalconfirmation was not available for seven patients.

In conclusion, although there is significant overlap ofthe CT findings for subpleural opacities, consolidationwith a subpleural and peribronchovascular distributionis highly suggestive of COP, and subpleural GGO is sug-gestive of NSIP. In addition, subpleural reticular or retic-ulonodular densities with a paucity of GGO suggestUIP, and subpleural consolidation accompanied withreticular densities is associated with fibrosis.

References

1. Gurney JW. Cross-sectional physiology of the lung. Radiology1991;178:1-10

2. Webb WR, Muller NL, Naidich DP. High-resolution CT of the lung,3rd ed. Lippincott Williams & Wilkins, 2000:41-108

3. Lynch DA, Travis WD, Muller NL, Galvin JR, Hansell DM,Grenier PA, et al. Idiopathic interstitial pneumonias: CT features.Radiology 2005;236:10-21

4. Epler GR, Colby TV, McLoud TC, Carrington CB, Gaensler EA.Bronchiolitis obliterans organizing pneumonia. N Engl J Med1985;312:152-158

5. Arakawa H, Kurihara Y, Niimi H, Nakajima Y, Johkoh T,Nakamura H. Bronchiolitis obliterans with organizing pneumoniaversus chronic eosinophilic pneumonia: High-resolution CT find-ings in 81 patients. AJR Am J Roentgenol 2001;176:1053-1058

6. Lee KS, Kullnig P, Hartman TE, Muller NL. Cryptogenic organiz-ing pneumonia: CT findings in 43 patients. AJR Am J Roentgenol1994;162:543-546

7. Akira M, Yamamoto S, Sakatani M. Bronchiolitis obliterans orga-nizing pneumonia manifesting as multiple large nodules or mass-es. AJR Am J Roentgenol 1998;170:291-295

8. Nishimura K, Itoh H. High-resolution computed tomographic fea-tures of bronchiolitis obliterans organizing pneumonia. Chest1992;102 Suppl1:26S-31S

9. Murphy JM, Schnyder P, Verschakelen J, Leuenberger P, FlowerCDR. Linear opacities on HRCT in bronchiolitis obliterans organiz-ing pneumonia. Eur Radiol 1999;9:1813-1817

10. Kim SJ, Lee KS, Ryu YH, Yoon YC, Choe KO, Kim TS, et al.Reversed halo sign on high-resolution CT of cryptogenic organiz-ing pneumonia: diagnostic implications. AJR Am J Roentgenol2003;180:1251-1254

11. Ujita M, Renzoni EA, Veeraraghavan S, Wells AU, Hansell DM.Organizing peumonia: perilobular pattern at thin-section CT.Radiology 2004;232:757-761

12. Katzenstein AL, Fiorelli RF. Nonspecific interstitial pneumonia/fi-brosis. Histologic features and clinical significance. Am J SurgPathol 1994;18:136-147

13. Tsubamoto M, Muller NL, Johkoh T, Ichikado K, Taniguchi H,Kondoh Y, et al. Pathologic subgroups of nonspecific interstitialpneumonia: differential diagnosis from other idiopathic interstitialpneumonias on high-resolution computed tomography. J ComputAssist Tomogr 2005;29:793-800

14. Hartman TE, Swensen SJ, Hansell DM, Colby TV, Myers JL,Tazelaar HD, et al. Nonspecific interstitial pneumonia: variable ap-pearance at high-resolution chest CT. Radiology 2000;217:701-705

15. Kim EY, Lee KS, Chung MP, Kwon OJ, Kim TS, Hwang JW.Nonspecific interstitial pneumonia with fibrosis: serial high-resolu-tion CT findings with functional correlation. AJR Am J Roentgenol1999;173:949-953

16. Wittram C, Mark EJ, McLoud TC. CT-histologic correlation of theATS/ERS 2002 classification of idiopathic interstitial pneumonias.Radiographics 2003;23:1057-1071

17. Liebow AA, Carrington CB. The interstitial pneumonias. In: SimonM, Potchen EJ, LeMay M, eds. Frontiers of pulmonary radiology.New York: Grune & Stratton, 1969:102-141

18. Chandler PW, Shin MS, Friedman SE, Myers JL, Katzenstein AL.Radiologic manifestations of bronchiolitis obliterans with organiz-ing pneumonia vs usual interstitial pneumonia. AJR Am JRoentgenol 1986;147:899-906

19. Souza CA, Muller NL, Flint J, Wright JL, Churg A. Idiopathic pul-monary fibrosis: spectrum of high-resolution CT findings. AJR AmJ Roentgenol 2005;185:1531-1539

20. MacDonald SL, Rubens MB, Hansell DM, Copley SJ, Desai SR, duBois RM, et al. Nonspecific interstitial pneumonia and usual inter-stitial pneumonia: comparative appearances at and diagnostic ac-curacy of thin-section CT. Radiology 2001;221:600-605

21. Mino M, Noma S, Taguchi Y, Tomii K, Kohri Y, Oida K.Pulmonary involvement in polymyositis and dermatomyositis: se-quential evaluation with CT. AJR Am J Roentgenol 1997;169:83-87

22. Bankier AA, Kiener HP, Wiesmayr MN, Fleischmann D, KontrusM, Herold CJ, et al. Discrete lung involvement in systemic lupuserythematosus: CT assessment. Radiology 1995;196:835-840

23. Carrington CB, Addington WW, Goff AM, Madoff IM, Marks A,Schwaber JR, et al. Chronic eosinophilic pneumonia. N Engl J Med1969;280:787-798

24. Mayo JR, Muller NL, Road J, Sisler J, Lillington G. Chroniceosinophilic pneumonia: CT findings in six cases. AJR Am J

Hee Seok Choi, et al : Assessment of Subpleural Opacities on High-Resolution CT

─ 448 ─

Page 9: Assessment of Subpleural Opacities on High-Resolution …€¦ · Assessment of Subpleural Opacities on ... Purpose: The purpose of this ... (No. Consolidation GGO Reticular or Nodular

Roentgenol 1989;153:727-73025. Johkoh T, Muller NL. Akira M, Ichikado K, Suga M, Ando M, et

al. Eosinophilic lung diseases: diagnostic accuracy of thin-sectionCT in 111 patients. Radiology 2000;216:773-780

26. Churg J. Strauss L. Allergic granulomatosis, allergic angiitis, andperiarteritis nodosa. Am J Pathol 1951;27:277-301

27. Worthy SA, Muller NL, Hansell DM, Flower CD. Churg-Strausssyndrome: the spectrum of pulmonary CT findings in 17 patients.

AJR Am J Roentgenol 1998;170:297-30028. Choi YH, Im JG, Han BK, Kim JH, Lee KY, Myoung NH. Thoracic

manifestation of Churg-Strauss syndrome: radiologic and clinicalfindings. Chest 2000;117:117-124

29. Johkoh T, Muller NL, Cartier Y, Kavanagh PV, Hartman TE,Akira M, et al. Idiopathic interstitial pneumonias: diagnostic accu-racy of thin-section CT in 129 patients. Radiology 1999;211:555-560

J Korean Radiol Soc 2007;57:441-449

─ 449 ─

대한영상의학회지 2007;57:441-449

고해상 CT상 흉막하 음영의 분석1

1동국대학교 의과대학 일산병원 영상의학과2고려대학교 의과대학 구로병원 영상의학과

3울산대학교 의과대학 서울아산병원 영상의학과

최희석·김정숙·강은영2·김학희3

목적: 흉막 하부 음영의 원인을 파악하는데 있어서 HRCT의 유용성을 알아보고자 하였다.

대상과 방법: 단순흉부X선 사진에서 흉막 하부 음영을 보인 환자 중에서 HRCT에서 흉막 하부에 음영을 보인 49

명을 대상으로 하였다. HRCT는 두 명의 영상의학과 의사가 합의로 분석하였다.

결과: 특발성기질화폐렴 14예, 비특이적간질성폐렴 13예, 상용간질성폐렴 10예, 결체조직 질환 혹은 약물 독성과

연관된 폐 섬유화 4예, 만성 호산구성폐렴 4예, Churg-Strauss syndrome 2예, 박리성간질성폐렴과 급성간질성폐

렴 각각 1예였다. 특발성기질화폐렴에서는 기관지 혈관을 따라 분포하는 폐경화(57%); 비특이적간질성폐렴에서는

간유리음영(69%)과 이와 연관된 부분적 망상음영(61%); 상용간질성폐렴에서는 망상음영 혹은 망상결절형 음영

음영과 적은 범위의 간유리음영(100%)을 보였다. 특발성기질화 폐렴, 비특이적간질성폐렴, 그리고 상용간질성폐렴

은 HRCT상 높은 민감도(86%, 85%, 90%)와 특이도(97%, 86%, 95%) 및 정확도(94%, 86%, 94%)를 보였다.

결론: 흉막 하부 음영을 보이는 질환들의 HRCT소견은 중복되지만, 흉막 하부 그리고 기관지 혈관을 따라 분포하

는 폐경화는 특발성기질화폐렴을 시사하며, 흉막 하부 간유리음영은 비특이적간질성폐렴을, 흉막 하부 망상음영 혹

은 망상결절형 음영과 적은 범위의 간유리음영은 상용간질성폐렴을, 흉막 하부 폐경화와 동반된 망상음영은 섬유

화를 시사한다.