- Email: [email protected]
Diagnostic Value of Quantitative Chest CT Scan in a Case of Spontaneous Pneumothorax
[
Chest Imaging and Pathology for Clinicians
]
Diagnostic Value of Quantitative Chest CT Scan in a Case of Spontaneous Pneumothorax Kathryn H. Melamed, MD; Fereidoun Abtin, MD; Igor Barjaktarevic, MD, PhD; and Christopher B. Cooper, MD
An 18-year-old woman with no previous medical history presented to an outside hospital facility with acute chest pain. She had mild shortness of breath, particularly with exertion, for the prior 2 months.
Case Presentation Two days prior to presentation, she suddenly developed sharp, pleuritic pain immediately after water polo practice. The pain was worse with exertion. She denied trauma to the chest or prolonged, deep submersion under water. She had no fevers, chills, rhinorrhea, sinus congestion, cough, or palpitations. She took no prescription or over-the-counter medications. She was currently on her college water polo team, and until this acute episode showed no functional limitation. She did not smoke tobacco or use other inhalational illicit drugs. She had no history of perinatal or childhood respiratory illness. Her parents, brother, and sister were healthy without any respiratory illness or connective tissues disease. Examination on presentation revealed normal vital signs, including a heart rate of 65 beats per minute, blood pressure of 113/70 mm Hg, and oxygen saturation of 100% while breathing room air. She was not in distress, and she was noted to be tall and thin. Her respiratory examination revealed decreased breath sounds at the left basilar and mid-lung zones, and her lungs were otherwise clear without wheezes or rales. The rest of her physical examination was normal and unremarkable.
AFFILIATIONS: From the Division of Pulmonary and Critical Care Medicine, Department of Medicine (Drs Melamed, Barjaktarevic, and Cooper), and the Department of Radiology (Dr Abtin), David Geffen School of Medicine at UCLA, Los Angeles, CA. CORRESPONDENCE TO: Kathryn H. Melamed, MD, David Geffen School of Medicine, University of California, Los Angeles, 10833 Le
chestjournal.org
CHEST 2017; 152(5):e109-e114
Chest radiography (Fig 1) revealed a large left pneumothorax with depression of the left hemidiaphragm, shift of the mediastinum to the right, and left apical blebs. Since she remained hemodynamically stable, emergency needle decompression was not necessary. Pediatric surgery was consulted. At their recommendation, she underwent
Figure 1 – Chest radiograph on admission, showing a large left pneumothorax (arrow) with depression of the left hemidiaphragm, shift of the mediastinum to the right, and left apical blebs.
Conte Ave, 37-131 CHS, Los Angeles, CA 90095; e-mail: kmelamed@ mednet.ucla.edu Copyright Ó 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved. DOI: http://dx.doi.org/10.1016/j.chest.2017.07.013
e109
Figure 2 – Histopathology of excised left upper lobe bullae, showing two representative sections (A, B) that include bullous emphysema with subpleural fibrosis and chronic inflammation.
video-assisted thoracoscopic surgery with resection of apical blebs and mechanical pleurodesis. Pathologic examination of the excised lung tissue (Fig 2) revealed subpleural blebs and bullous emphysema with fibrosis and chronic inflammation.
She was referred to a pulmonary specialist at our tertiary care center for follow-up after this acute event and subsequent surgical intervention. Pulmonary function test results were consistent with mild obstructive lung disease, with a ratio of FEV1 to FVC
Figure 3 – High-resolution CT scan of the chest without contrast after pleurodesis. Imaging was performed on a Siemens Sensation 64 CT scanner obtained at 1.0-mm slice thickness and with multiplanar reconstruction at the end of inspiration. A-C, Decreased lung parenchymal density in the left upper lobe, concerning for bronchial atresia or Swyer-James syndrome. D, The lower lobes were unaffected.
e110 Chest Imaging and Pathology for Clinicians
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152#5 CHEST NOVEMBER 2017
]
Figure 4 – Representative axial (A), sagittal (B), and coronal (C) images from the chest CT scan. Quantitative imaging analysis was then applied to the respective images (D-F) and highlights the areas of emphysema in the bilateral upper lobes (green), middle lobe (red), and bilateral lower lobes (yellow). Computational analysis, using –950 Hounsfield units as a cutoff, shows that the left upper lobe consists of 19% emphysematous lung and that the middle lobe is 10% emphysematous. The remaining lobes have less than 8% lung tissue that is below the Hounsfield unit cutoff for emphysema, which is consistent with normal lung parenchyma.
of 69%, and an FEV1 of 84% predicted. The total lung capacity was 122% predicted, and the diffusion capacity was normal. An echocardiogram showed normal biventricular function and no valve dysfunction. A high-resolution CT scan of the chest without intravenous contrast was performed (Fig 3), which showed decreased lung parenchymal density in the left upper lobe, as well as dilation of the left upper lobe anterior segmental airway with retained secretions. The initial diagnostic considerations were bronchial atresia
chestjournal.org
and Swyer-James syndrome. Quantitative imaging analysis (QIA) was applied to the CT images (Fig 4). Using an emphysema score cutoff of –950 Hounsfield units, there was increased emphysema noted in the left upper lobe (19% of the lobar volume) and middle lobe (10% of the lobar volume). The remaining lobes had 5% to 3% of their lung volume in the emphysematous range.
What is the diagnosis?
e111
Diagnosis: Congenital lobar emphysema Discussion Clinical Discussion
Congenital lobar emphysema (CLE) is characterized by overdistension of the one or more affected lobe(s) of the lung with compensatory compression or shift of the others. It is most often diagnosed in infancy (average age of 5 months at diagnosis), although it can rarely present later in childhood or adulthood.1 The incidence of CLE is 1 in 20,000, with a higher prevalence in men. The left upper lobe is the most commonly affected lobe, the middle lobe is the second most common site, and the lower lobes tend not to be affected.2 CLE is thought to develop from extrinsic or intrinsic bronchial obstruction during fetal development or an alveolar abnormality. Typically, bronchial cartilage dysplasia or obstruction leads to bronchial collapse and then airways obstruction with exhalation. Persistent airways obstruction leads to air trapping and lobar expansion. However, in up to 50% of cases no pathologic airway abnormality is identified. Rarely, CLE is associated with other cardiopulmonary malformations, such as bronchial atresia, bronchogenic cysts, patent ductus arteriosus, pulmonary artery sling, anomalous pulmonary artery venous return, teratoma, or neuroblastoma.1,3 Patients typically present in infancy with significant symptoms of dyspnea, tachypnea, wheezing, cough, and cyanosis.1,3 Less often, patients remain asymptomatic, and CLE is discovered incidentally on chest imaging later in life. Diagnosis is made on the basis of clinical history, chest radiograph, and CT scans of the chest showing emphysema of the affected lobe with associated hyperinflation. Nuclear ventilation-perfusion imaging can also show reduced ventilation and perfusion of the affected lobe.1 Of those presenting with symptoms in infancy, about 80% survive. Surgical resection is often proposed, but studies show that unless very symptomatic, surgical intervention and conservative management may have similar outcomes.1 When CLE is identified later in life, patients are often treated with clinical observation.3,4 There are case reports that suggest surgical resection can be effective in older children or adults if patients have significant obstruction on pulmonary function testing and are notably symptomatic.5 There has been one other case report of an adult presenting with spontaneous pneumothorax secondary to CLE, which in this case
e112 Chest Imaging and Pathology for Clinicians
was located in the middle lobe.6 That patient underwent video-assisted thoracoscopic surgery with resection of the bullae and pleurodesis, and no further intervention was needed. CLE diagnosed in adulthood remains a rare disease, and presentation by spontaneous pneumothorax is even more esoteric. Radiologic Discussion
The typical radiographic appearance of CLE on chest radiograph and chest CT scan is a hyperinflated lobe, typically the left upper lobe or middle lobe. The differential diagnosis on imaging includes bronchial atresia, which is characterized by mucoceles at the end of bronchi; congenital pulmonary airway malformation, which includes cysts attached to airway bronchi; and Swyer-James syndrome, which is an acquired localized emphysema secondary to a bronchopulmonary infection and resultant bronchiectasis.7 Details of these disease entities and their radiologic features can be found in Table 1.8 Understanding these hallmark radiographic features can help identify congenital pulmonary lesions, even when they present well into adulthood. Radiographic distinction between bronchial atresia and CLE can be particularly difficult. Both diseases have a predilection for the left upper and middle lobes, resulting in segmental or lobar hyperinflation. Bronchial atresia is noted by a segmental airway that did not properly develop, resulting in a blind airway with retained secretions and distal segmental hyperinflation. Radiographically this can be difficult to distinguish from CLE, as was the case here. In addition, these two entities can exist concurrently in one patient such that bronchial atresia is the initial airways defect that leads to the development of CLE. Quantitative imaging analysis (QIA), which allows for precise identification of lung tissue density by Hounsfield units (HU), can help differentiate otherwise subtle radiographic diagnoses. This imaging analysis technique can be applied to chest CT images to accurately identify emphysematous lung.9,10 On the basis of several studies correlating imaging studies with macroscopic and microscopic histopathologic review, a cutoff of less than –950 HU is the most accurate threshold used to identify emphysematous lung.11-13 Using this cutoff, QIA software then calculates the percentage of lung volume that meets criteria for emphysema by HU. Six to eight percent of normal lung volume will be less than –950 HU,9 and therefore if any lobe is occupied by greater than 8% of low-density lung it is considered emphysematous. Data also show that
[
152#5 CHEST NOVEMBER 2017
]
TABLE 1
] Pathogenesis and Radiographic Appearance of Congenital Obstructive Pulmonary Pathology8
Diagnosis
Pathogenesis
Common Location
Radiographic Features
Congenital lobar emphysema
Any cause of bronchial obstruction (e.g., cartilage defect, bronchial mucous plugs) leads to distal air trapping
LUL or ML
Overinflation of the affected lobe with air trapping on expiration
Bronchial atresia
Fetal interruption of bronchial arterial blood supply / disconnect between tip of the bronchial bud proximal segments
Anteroposterior segment of LUL; segmental bronchi of RUL, ML
Overinflation of peripheral lung; dilated bronchi retained secretions; dilated bronchi taper distally; hilar mass
Cystic adenomatoid malformation
Abnormally growing bronchioles form cysts instead of alveoli
Unilateral, affecting an entire lung rather than lobe (most often)
Complex cystic mass, frequent concurrent pneumonia; by adulthood cysts expand to involve the entire hemithorax with shift of the mediastinum
Swyer-James
Acquired; bronchopulmonary infection / bronchiectasis / localized emphysema
Any lobe
Affected lobe is normal to smaller in size; asymmetrical but bilateral disease due to concurrent postinfectious obliterative bronchiolitis; matched decrease in ventilation and perfusion
Intralobar bronchopulmonary sequestration
Error in tracheobronchial branching leaves a segment of lung with its embryonic systemic arterial supply
Lower lobes (left more common than right)
Consolidative opacity, mass air fluid level, cystic structure; systemic arterial supply seen; can lead to localized overinflation if recurrent infections occur
LUL ¼ left upper lobe; ML ¼ middle lobe; RUL ¼ right upper lobe.
QIA is more accurate at identifying emphysema than subjective chest CT analysis by trained radiologists.14 Chest CT scanning with QIA has been applied to a prior case report of CLE, and here helped to accurately distinguish it from other congenital or structural abnormalities.7 In our case, QIA was able to identify two emphysematous lobes, most notably the left upper lobe and a moderately affected middle lobe (Fig 4), the hallmark features of CLE. While many of the other diagnoses considered here may have decreased lung density or air trapping to some degree, the distribution and diffuse nature of the decreased lung density in the left upper and right middle lobes are characteristic of CLE. Bronchial atresia, on the other hand, tends to affect a segment of a lobe, rather than an entire lobe, and often is accompanied by a mucocele or retained secretions. In addition, these images are distinct from simple hyperinflation or air trapping, which is generally seen only on end-expiratory images. Instead, this patient demonstrates low attenuation and emphysema during inspiration, and hence air trapping alone is less likely.
chestjournal.org
Our QIA findings clinched the diagnosis of CLE, which presented in a rare and atypical fashion in this 18-yearold woman with a spontaneous left-sided pneumothorax. Bronchial atresia remains a diagnostic consideration in this case, and may in fact coexist in this patient. However, the extent of lobar emphysematous involvement in the left upper and right middle lobes, which was identified by QIA, is most consistent with a diagnosis of CLE. It should be noted that the chest CT scan performed in this patient was after surgical intervention and pleurodesis. However, since only a small wedge resection was performed, surgical intervention should not have affected the QIA results. Pathologic Discussion
In about one-half of the cases of CLE, an identifiable bronchial lesion is found on pathologic examination of the lung. In these cases, bronchial cartilage dysplasia, paucity of bronchial cartilage, or bronchial obstruction from mucous plugging or otherwise can be seen.5,15
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Often CLE is associated with polyalveolosis, resulting in increased total alveolar number, but the normal number of airways and arteries.15 The remaining CLE cases do not have any identifiable or distinguishing feature on pathology, as was the case with this patient. In these cases, other diagnostic modalities, namely imaging studies, are necessary to make the diagnosis.
Other contributions: CHEST worked with the authors to ensure that the Journal policies on patient consent to report information were met.
References 1. Ozcelik U, Gocmen A, Kiner N, Dogru D, Dilber E, Yalcin EG. Congenital lobar emphysema: evaluation and long-term follow up of thirty cases as a single center. Pediatr Pulmonol. 2003;35(5):384-391. 2. Thakral CL, Maji DC, Sajwani MJ. Congenital lobar emphysema: experience with 21 cases. Pediatr Surg Int. 2001;17(2-3):88-91. 3. Mei-Zahav M, Konen O, Manson D, Langer JC. Is congenital lobar emphysema a surgical disease? J Pediatr Surg. 2006;41(6):1058-1061.
Conclusions After the diagnosis of CLE was made in this patient, no further workup or treatment was performed. Since she had already undergone pleurodesis of the left lung, her risk of pneumothorax was thought to be low. She had no ongoing symptoms of dyspnea, and as such no surgical intervention on the left upper or right middle lobes was needed. The patient was discharged from the pulmonary clinic and given clearance to return to her athletic activity. Congenital lobar emphysema is a rare lung disease that typically presents with dyspnea and hypoxia in infancy. Patients presenting later in life are uncommon, and often the diagnosis of CLE in these cases is difficult to make. Here we describe an adult patient whose first presentation of CLE was a spontaneous pneumothorax. The diagnosis of CLE was made using a novel imaging modality, chest CT scanning with quantitative imaging analysis. When CLE presents as an incidental finding in adulthood, conservative management is recommended.
Acknowledgments Financial/nonfinancial disclosures: The authors have reported to CHEST the following: I. B. has consulted with Astra Zeneca, CSL Behring, and Grifols and has received research grants from Amgen and GE Healthcare. C. B. C. reports grants from Equinox Health Clubs, personal fees from Equinox Health Clubs, grants from Amgen, personal fees from PulmonX, personal fees from Boehringer Ingelheim, personal fees from GlaxoSmithKline, grants from Spiration, and personal fees from Spiration, outside the submitted work; and part-time work on scientific engagement for the GlaxoSmithKline Global Respiratory Franchise. F. A. has consulted with MedQIA, Spiration, and Pulmonx. None declared (K. H. M.).
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4. Man DW, Hamdy MH, Hendry GM, Bisset WH, Forfar JO. Congenital lobar emphysema: problems in diagnosis and management. Arch Dis Child. 1983;58(9):709-712. 5. McDonald CF, Pierce RJ, Barter CE, Chou ST, Daniel FJ. Congenital lobar emphysema requiring surgery in adult life. Aust N Z J Med. 1986;16(4):501-505. 6. Muramatsu T, Furuichi M, Nishii T, Ishimoto S, Shiono M. Lobar emphysema with pneumothorax in an adult: report of a case. Surg Today. 2013;43(5):539-541. 7. Pike D, Mohan S, Ma W, Lewis JF, Parraga G. Pulmonary imaging abnormalities in an adult case of congenital lobar emphysema. J Radiol Case Rep. 2015;9(2):9-15. 8. Zylak CJ, Eyler WR, Spizarny DL, Stone CH. Developmental lung anomalies in the adult: radiologic-pathologic correlation. Radiographics. 2002;22:S25-S43. 9. Heussel CP, Herth FJ, Kappes J, et al. Fully automatic quantitative assessment of emphysema in computed tomography: comparison with pulmonary function testing and normal values. Eur Radiol. 2009;19(10):2391-2402. 10. Kim SS, Seo JB, Kim N, et al. Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density. Eur J Radiol. 2014;83(1):57-63. 11. Gevenois PA, de Maertalaer V, De Vuyst P, Zanen J, Yernault JC. Comparison of computed density and macroscopic morphometry in pulmonary emphysema. Am J Respir Crit Care Med. 1995;152(2): 653-657. 12. Gevenois PA, De Vuyst P, de Maertalaer V, et al. Comparison of computed density and microscopic morphometry in pulmonary emphysema. Am J Respir Crit Care Med. 1996;154(1):187-192. 13. Hoffman EA, Ahmed FS, Baumhauer H, et al. Variation in the percent of emphysema-like lung in a healthy, nonsmoking multiethnic sample: the MESA lung study. Ann Am Thorac Soc. 2014;11(6):898-907. 14. Bankier AA, De Maertelaer V, Keyzer C, Gevenois PA. Pulmonary emphysema: subjective visual grading versus objective quantification with macroscopic morphometry and thin-section CT densitometry. Radiology. 1999;211(3):851-858. 15. Olutoye OO, Coleman BG, Hubbard AM, Adzick NS. Prenatal diagnosis and management of congenital lobar emphysema. J Pediatr Surg. 2000;35(5):792-795.
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152#5 CHEST NOVEMBER 2017
]
Chest Imaging and Pathology for Clinicians
]
Diagnostic Value of Quantitative Chest CT Scan in a Case of Spontaneous Pneumothorax Kathryn H. Melamed, MD; Fereidoun Abtin, MD; Igor Barjaktarevic, MD, PhD; and Christopher B. Cooper, MD
An 18-year-old woman with no previous medical history presented to an outside hospital facility with acute chest pain. She had mild shortness of breath, particularly with exertion, for the prior 2 months.
Case Presentation Two days prior to presentation, she suddenly developed sharp, pleuritic pain immediately after water polo practice. The pain was worse with exertion. She denied trauma to the chest or prolonged, deep submersion under water. She had no fevers, chills, rhinorrhea, sinus congestion, cough, or palpitations. She took no prescription or over-the-counter medications. She was currently on her college water polo team, and until this acute episode showed no functional limitation. She did not smoke tobacco or use other inhalational illicit drugs. She had no history of perinatal or childhood respiratory illness. Her parents, brother, and sister were healthy without any respiratory illness or connective tissues disease. Examination on presentation revealed normal vital signs, including a heart rate of 65 beats per minute, blood pressure of 113/70 mm Hg, and oxygen saturation of 100% while breathing room air. She was not in distress, and she was noted to be tall and thin. Her respiratory examination revealed decreased breath sounds at the left basilar and mid-lung zones, and her lungs were otherwise clear without wheezes or rales. The rest of her physical examination was normal and unremarkable.
AFFILIATIONS: From the Division of Pulmonary and Critical Care Medicine, Department of Medicine (Drs Melamed, Barjaktarevic, and Cooper), and the Department of Radiology (Dr Abtin), David Geffen School of Medicine at UCLA, Los Angeles, CA. CORRESPONDENCE TO: Kathryn H. Melamed, MD, David Geffen School of Medicine, University of California, Los Angeles, 10833 Le
chestjournal.org
CHEST 2017; 152(5):e109-e114
Chest radiography (Fig 1) revealed a large left pneumothorax with depression of the left hemidiaphragm, shift of the mediastinum to the right, and left apical blebs. Since she remained hemodynamically stable, emergency needle decompression was not necessary. Pediatric surgery was consulted. At their recommendation, she underwent
Figure 1 – Chest radiograph on admission, showing a large left pneumothorax (arrow) with depression of the left hemidiaphragm, shift of the mediastinum to the right, and left apical blebs.
Conte Ave, 37-131 CHS, Los Angeles, CA 90095; e-mail: kmelamed@ mednet.ucla.edu Copyright Ó 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved. DOI: http://dx.doi.org/10.1016/j.chest.2017.07.013
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Figure 2 – Histopathology of excised left upper lobe bullae, showing two representative sections (A, B) that include bullous emphysema with subpleural fibrosis and chronic inflammation.
video-assisted thoracoscopic surgery with resection of apical blebs and mechanical pleurodesis. Pathologic examination of the excised lung tissue (Fig 2) revealed subpleural blebs and bullous emphysema with fibrosis and chronic inflammation.
She was referred to a pulmonary specialist at our tertiary care center for follow-up after this acute event and subsequent surgical intervention. Pulmonary function test results were consistent with mild obstructive lung disease, with a ratio of FEV1 to FVC
Figure 3 – High-resolution CT scan of the chest without contrast after pleurodesis. Imaging was performed on a Siemens Sensation 64 CT scanner obtained at 1.0-mm slice thickness and with multiplanar reconstruction at the end of inspiration. A-C, Decreased lung parenchymal density in the left upper lobe, concerning for bronchial atresia or Swyer-James syndrome. D, The lower lobes were unaffected.
e110 Chest Imaging and Pathology for Clinicians
[
152#5 CHEST NOVEMBER 2017
]
Figure 4 – Representative axial (A), sagittal (B), and coronal (C) images from the chest CT scan. Quantitative imaging analysis was then applied to the respective images (D-F) and highlights the areas of emphysema in the bilateral upper lobes (green), middle lobe (red), and bilateral lower lobes (yellow). Computational analysis, using –950 Hounsfield units as a cutoff, shows that the left upper lobe consists of 19% emphysematous lung and that the middle lobe is 10% emphysematous. The remaining lobes have less than 8% lung tissue that is below the Hounsfield unit cutoff for emphysema, which is consistent with normal lung parenchyma.
of 69%, and an FEV1 of 84% predicted. The total lung capacity was 122% predicted, and the diffusion capacity was normal. An echocardiogram showed normal biventricular function and no valve dysfunction. A high-resolution CT scan of the chest without intravenous contrast was performed (Fig 3), which showed decreased lung parenchymal density in the left upper lobe, as well as dilation of the left upper lobe anterior segmental airway with retained secretions. The initial diagnostic considerations were bronchial atresia
chestjournal.org
and Swyer-James syndrome. Quantitative imaging analysis (QIA) was applied to the CT images (Fig 4). Using an emphysema score cutoff of –950 Hounsfield units, there was increased emphysema noted in the left upper lobe (19% of the lobar volume) and middle lobe (10% of the lobar volume). The remaining lobes had 5% to 3% of their lung volume in the emphysematous range.
What is the diagnosis?
e111
Diagnosis: Congenital lobar emphysema Discussion Clinical Discussion
Congenital lobar emphysema (CLE) is characterized by overdistension of the one or more affected lobe(s) of the lung with compensatory compression or shift of the others. It is most often diagnosed in infancy (average age of 5 months at diagnosis), although it can rarely present later in childhood or adulthood.1 The incidence of CLE is 1 in 20,000, with a higher prevalence in men. The left upper lobe is the most commonly affected lobe, the middle lobe is the second most common site, and the lower lobes tend not to be affected.2 CLE is thought to develop from extrinsic or intrinsic bronchial obstruction during fetal development or an alveolar abnormality. Typically, bronchial cartilage dysplasia or obstruction leads to bronchial collapse and then airways obstruction with exhalation. Persistent airways obstruction leads to air trapping and lobar expansion. However, in up to 50% of cases no pathologic airway abnormality is identified. Rarely, CLE is associated with other cardiopulmonary malformations, such as bronchial atresia, bronchogenic cysts, patent ductus arteriosus, pulmonary artery sling, anomalous pulmonary artery venous return, teratoma, or neuroblastoma.1,3 Patients typically present in infancy with significant symptoms of dyspnea, tachypnea, wheezing, cough, and cyanosis.1,3 Less often, patients remain asymptomatic, and CLE is discovered incidentally on chest imaging later in life. Diagnosis is made on the basis of clinical history, chest radiograph, and CT scans of the chest showing emphysema of the affected lobe with associated hyperinflation. Nuclear ventilation-perfusion imaging can also show reduced ventilation and perfusion of the affected lobe.1 Of those presenting with symptoms in infancy, about 80% survive. Surgical resection is often proposed, but studies show that unless very symptomatic, surgical intervention and conservative management may have similar outcomes.1 When CLE is identified later in life, patients are often treated with clinical observation.3,4 There are case reports that suggest surgical resection can be effective in older children or adults if patients have significant obstruction on pulmonary function testing and are notably symptomatic.5 There has been one other case report of an adult presenting with spontaneous pneumothorax secondary to CLE, which in this case
e112 Chest Imaging and Pathology for Clinicians
was located in the middle lobe.6 That patient underwent video-assisted thoracoscopic surgery with resection of the bullae and pleurodesis, and no further intervention was needed. CLE diagnosed in adulthood remains a rare disease, and presentation by spontaneous pneumothorax is even more esoteric. Radiologic Discussion
The typical radiographic appearance of CLE on chest radiograph and chest CT scan is a hyperinflated lobe, typically the left upper lobe or middle lobe. The differential diagnosis on imaging includes bronchial atresia, which is characterized by mucoceles at the end of bronchi; congenital pulmonary airway malformation, which includes cysts attached to airway bronchi; and Swyer-James syndrome, which is an acquired localized emphysema secondary to a bronchopulmonary infection and resultant bronchiectasis.7 Details of these disease entities and their radiologic features can be found in Table 1.8 Understanding these hallmark radiographic features can help identify congenital pulmonary lesions, even when they present well into adulthood. Radiographic distinction between bronchial atresia and CLE can be particularly difficult. Both diseases have a predilection for the left upper and middle lobes, resulting in segmental or lobar hyperinflation. Bronchial atresia is noted by a segmental airway that did not properly develop, resulting in a blind airway with retained secretions and distal segmental hyperinflation. Radiographically this can be difficult to distinguish from CLE, as was the case here. In addition, these two entities can exist concurrently in one patient such that bronchial atresia is the initial airways defect that leads to the development of CLE. Quantitative imaging analysis (QIA), which allows for precise identification of lung tissue density by Hounsfield units (HU), can help differentiate otherwise subtle radiographic diagnoses. This imaging analysis technique can be applied to chest CT images to accurately identify emphysematous lung.9,10 On the basis of several studies correlating imaging studies with macroscopic and microscopic histopathologic review, a cutoff of less than –950 HU is the most accurate threshold used to identify emphysematous lung.11-13 Using this cutoff, QIA software then calculates the percentage of lung volume that meets criteria for emphysema by HU. Six to eight percent of normal lung volume will be less than –950 HU,9 and therefore if any lobe is occupied by greater than 8% of low-density lung it is considered emphysematous. Data also show that
[
152#5 CHEST NOVEMBER 2017
]
TABLE 1
] Pathogenesis and Radiographic Appearance of Congenital Obstructive Pulmonary Pathology8
Diagnosis
Pathogenesis
Common Location
Radiographic Features
Congenital lobar emphysema
Any cause of bronchial obstruction (e.g., cartilage defect, bronchial mucous plugs) leads to distal air trapping
LUL or ML
Overinflation of the affected lobe with air trapping on expiration
Bronchial atresia
Fetal interruption of bronchial arterial blood supply / disconnect between tip of the bronchial bud proximal segments
Anteroposterior segment of LUL; segmental bronchi of RUL, ML
Overinflation of peripheral lung; dilated bronchi retained secretions; dilated bronchi taper distally; hilar mass
Cystic adenomatoid malformation
Abnormally growing bronchioles form cysts instead of alveoli
Unilateral, affecting an entire lung rather than lobe (most often)
Complex cystic mass, frequent concurrent pneumonia; by adulthood cysts expand to involve the entire hemithorax with shift of the mediastinum
Swyer-James
Acquired; bronchopulmonary infection / bronchiectasis / localized emphysema
Any lobe
Affected lobe is normal to smaller in size; asymmetrical but bilateral disease due to concurrent postinfectious obliterative bronchiolitis; matched decrease in ventilation and perfusion
Intralobar bronchopulmonary sequestration
Error in tracheobronchial branching leaves a segment of lung with its embryonic systemic arterial supply
Lower lobes (left more common than right)
Consolidative opacity, mass air fluid level, cystic structure; systemic arterial supply seen; can lead to localized overinflation if recurrent infections occur
LUL ¼ left upper lobe; ML ¼ middle lobe; RUL ¼ right upper lobe.
QIA is more accurate at identifying emphysema than subjective chest CT analysis by trained radiologists.14 Chest CT scanning with QIA has been applied to a prior case report of CLE, and here helped to accurately distinguish it from other congenital or structural abnormalities.7 In our case, QIA was able to identify two emphysematous lobes, most notably the left upper lobe and a moderately affected middle lobe (Fig 4), the hallmark features of CLE. While many of the other diagnoses considered here may have decreased lung density or air trapping to some degree, the distribution and diffuse nature of the decreased lung density in the left upper and right middle lobes are characteristic of CLE. Bronchial atresia, on the other hand, tends to affect a segment of a lobe, rather than an entire lobe, and often is accompanied by a mucocele or retained secretions. In addition, these images are distinct from simple hyperinflation or air trapping, which is generally seen only on end-expiratory images. Instead, this patient demonstrates low attenuation and emphysema during inspiration, and hence air trapping alone is less likely.
chestjournal.org
Our QIA findings clinched the diagnosis of CLE, which presented in a rare and atypical fashion in this 18-yearold woman with a spontaneous left-sided pneumothorax. Bronchial atresia remains a diagnostic consideration in this case, and may in fact coexist in this patient. However, the extent of lobar emphysematous involvement in the left upper and right middle lobes, which was identified by QIA, is most consistent with a diagnosis of CLE. It should be noted that the chest CT scan performed in this patient was after surgical intervention and pleurodesis. However, since only a small wedge resection was performed, surgical intervention should not have affected the QIA results. Pathologic Discussion
In about one-half of the cases of CLE, an identifiable bronchial lesion is found on pathologic examination of the lung. In these cases, bronchial cartilage dysplasia, paucity of bronchial cartilage, or bronchial obstruction from mucous plugging or otherwise can be seen.5,15
e113
Often CLE is associated with polyalveolosis, resulting in increased total alveolar number, but the normal number of airways and arteries.15 The remaining CLE cases do not have any identifiable or distinguishing feature on pathology, as was the case with this patient. In these cases, other diagnostic modalities, namely imaging studies, are necessary to make the diagnosis.
Other contributions: CHEST worked with the authors to ensure that the Journal policies on patient consent to report information were met.
References 1. Ozcelik U, Gocmen A, Kiner N, Dogru D, Dilber E, Yalcin EG. Congenital lobar emphysema: evaluation and long-term follow up of thirty cases as a single center. Pediatr Pulmonol. 2003;35(5):384-391. 2. Thakral CL, Maji DC, Sajwani MJ. Congenital lobar emphysema: experience with 21 cases. Pediatr Surg Int. 2001;17(2-3):88-91. 3. Mei-Zahav M, Konen O, Manson D, Langer JC. Is congenital lobar emphysema a surgical disease? J Pediatr Surg. 2006;41(6):1058-1061.
Conclusions After the diagnosis of CLE was made in this patient, no further workup or treatment was performed. Since she had already undergone pleurodesis of the left lung, her risk of pneumothorax was thought to be low. She had no ongoing symptoms of dyspnea, and as such no surgical intervention on the left upper or right middle lobes was needed. The patient was discharged from the pulmonary clinic and given clearance to return to her athletic activity. Congenital lobar emphysema is a rare lung disease that typically presents with dyspnea and hypoxia in infancy. Patients presenting later in life are uncommon, and often the diagnosis of CLE in these cases is difficult to make. Here we describe an adult patient whose first presentation of CLE was a spontaneous pneumothorax. The diagnosis of CLE was made using a novel imaging modality, chest CT scanning with quantitative imaging analysis. When CLE presents as an incidental finding in adulthood, conservative management is recommended.
Acknowledgments Financial/nonfinancial disclosures: The authors have reported to CHEST the following: I. B. has consulted with Astra Zeneca, CSL Behring, and Grifols and has received research grants from Amgen and GE Healthcare. C. B. C. reports grants from Equinox Health Clubs, personal fees from Equinox Health Clubs, grants from Amgen, personal fees from PulmonX, personal fees from Boehringer Ingelheim, personal fees from GlaxoSmithKline, grants from Spiration, and personal fees from Spiration, outside the submitted work; and part-time work on scientific engagement for the GlaxoSmithKline Global Respiratory Franchise. F. A. has consulted with MedQIA, Spiration, and Pulmonx. None declared (K. H. M.).
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