CT of Diffuse Tracheal Diseases

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1 Residents Section Structured Review rticle hung et al. T of the Trachea and entral irways Residents Section Structured Review rticle Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved Residents inradiology Jonathan H. hung 1 Jeffrey P. Kanne 2 Matthew D. Gilman 1 hung JH, Kanne JP, Gilman MD Keywords: Mounier-Kuhn syndrome, saber-sheath trachea, trachea, tracheal stenosis, tracheomalacia, Wegener granulomatosis DOI: /JR Received December 23, 2009; accepted after revision February 14, Department of Radiology, Massachusetts General Hospital, 55 Fruit St., FND-202, oston, M ddress correspondence to M. D. Gilman (mgilman@partners.org). ME This article is available for ME credit. See for more information. WE This is a Web exclusive article. JR 2011; 196:W240 W X/11/1963 W240 merican Roentgen Ray Society T of Diffuse Tracheal Diseases R adiologists can be instrumental in the diagnosis of tracheal abnormalities. Patients are often initially misdiagnosed with asthma or other obstructive lung disease because there is considerable overlap among the clinical presentation of these ailments and diffuse tracheal diseases. lthough the trachea can be imaged with chest radiography or fluoroscopy, T is the imaging test of choice to evaluate the trachea and central airways. MDT provides high-resolution images that can be used to generate multiplanar reformations, minimum intensity projections, 3D volume-rendered images, and virtual bronchoscopic images. In this article, we will illustrate T findings of diffuse nonmalignant tracheal diseases, emphasizing key differences that aid in diagnosis (Table 1). Key Points 1. T is currently the primary noninvasive examination to evaluate the trachea because it offers multiplanar capabilities, evaluates the morphology of the tracheal wall and lumen, and can be acquired in seconds. 2. The trachea is supported by -shaped cartilaginous rings anteriorly; the posterior trachea is primarily supported by the thin trachealis muscle. 3. The lunate-shaped trachea on inspiration is highly suggestive of tracheomalacia. 4. Traditionally, collapse of greater than 50% of the trachea during expiration was defined as tracheomalacia; however, recent evidence suggests that greater than 50% dynamic expiratory collapse can be seen in healthy patients. 5. In saber-sheath trachea, only the coronal diameter of the intrathoracic trachea is narrowed; primarily men with chronic obstructive pulmonary disease are affected. 6. The posterior wall of the trachea and the central bronchi are classically spared in both relapsing polychondritis and tracheobronchopathia osteochondroplastica. However, the presence of focal coarse calcification and ossification is highly suggestive of tracheobronchopathia osteochondroplastica rather than relapsing polychondritis. 7. Nodular calcification of the trachea is common in tracheobronchopathia osteochondroplastica and amyloidosis. However, amyloidosis tends to involve the airway concentrically, as opposed to tracheobronchopathia osteochondroplastica which spares the posterior wall. 8. Wegener granulomatosis most often affects the subglottic trachea but can be diffuse or multifocal. 9. Mounier-Kuhn syndrome is unique among the diffuse tracheal diseases in that it results in diffuse airway dilatation. Diverticula project between the cartilaginous rings giving the trachea and proximal bronchi a corrugated appearance. Normal natomy The trachea is composed of approximately shaped anterior cartilaginous rings that support the trachea during expiration. n inner mucosal layer, a submucosal layer, cartilage and muscle, and an adventitial layer comprise the tracheal wall. The posterior wall is formed primarily by the thin trachealis muscle, which lacks cartilaginous support (Fig. 1). The coronal diameter of the normal trachea ranges from 13 to 25 mm in men and from 10 to 21 mm in women, and the sagittal diameter of the normal trachea ranges from 13 to 27 mm in men and from 10 to 23 mm in women [1]. t end expiration, the trachea normally decreases in cross-sectional area, primarily from anterior movement of the posterior wall; there is wide variation in the degree of tracheal expiratory collapse [2, 3]. The arterial supply W240 JR:196, March 2011

2 T of the Trachea and entral irways Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved TLE 1: Imaging Findings of Various Diffuse Tracheal Diseases Tracheal Disease Tracheomalacia Saber-sheath trachea Relapsing polychondritis Tracheobronchopathia osteochondroplastica myloidosis Wegener granulomatosis Mounier-Kuhn syndrome Sarcoidosis T ppearance Severe expiratory collapse of the tracheal lumen; lunate-shaped trachea Decreased coronal diameter with concomitant increase in sagittal diameter Thickening of the cartilaginous trachea with sparing of the posterior membrane alcified or ossified nodules in the cartilaginous trachea with sparing of the posterior membrane alcified or ossified nodular or concentric tracheal wall thickening ircumferential tracheal wall thickening or cartilage defects; subglottic region most often involved Tracheal diameter > 3 cm; main bronchial diameter > 2.4 cm; scalloping of tracheal wall and diverticula Secondary tracheal narrowing from lymphadenopathy or primary tracheal narrowing from tracheal noncaseating granulomas of the trachea is derived from a number of sources including the inferior thyroid artery, the bronchial arteries, and the intercostal arteries. Nonpathologic senescent tracheal calcification is more common in women and tends to be diffuse; calcification occurs along the normal contour of the trachea. Nodular focal calcification suggests underlying disease. Tracheomalacia Tracheomalacia arises from weakness of the tracheobronchial walls and hypotonia in the myoelastic elements. In patients with tracheomalacia, collapse of the intrathoracic trachea secondary to increased intrathoracic pressure during expiration is characteristic and is accentuated during forced expiration [1]. auses of tracheomalacia include long-term intubation or other trauma, congenital abnormalities, chronic extrinsic compression (vascular ring or sling), chronic obstructive pulmonary disease, chronic inflammation, and infection [1]. Traditionally, collapse of greater than 50% of the trachea on T during expiration was defined as tracheomalacia [1] (Fig. 2). Tracheal Narrowing Wall Thickened Wall alcification haracteristically, the posterior membranous trachea bows anteriorly, producing an upside down U-shaped air column on transverse T termed the frown sign [4] (Fig. 2). However, recent evidence suggests that tracheal collapse of greater than 50% during dynamic expiration can be seen in up to 78% of healthy patients [3]. In a minority of patients, the trachea may have a lunate configuration during inspiration that is, the trachea is characterized by a coronal diameter that is greater than the sagittal diameter. This finding is highly suggestive of tracheomalacia and can be corroborated with dynamic expiratory T [4] (Fig. 3). In cases not resulting from another diffuse tracheal disease such as relapsing polychondritis or Wegener granulomatosis, the tracheal wall usually has a normal thickness, thereby helping differentiate tracheomalacia from other diffuse tracheal diseases [1]. Saber-Sheath Trachea Saber-sheath trachea is a common tracheal abnormality occurring almost exclusively Useful Differentiators Yes No No Tracheal collapse; history of predisposing condition or trauma Yes No No haracteristic bullet-shaped trachea on axial T; history or imaging findings suggesting chronic obstructive pulmonary disease Yes Yes Sometimes Sparing of the posterior trachea; cartilaginous abnormalities of the ears or nose Yes Yes lways Nodular calcified or nodular ossified tracheal wall thickening sparing the posterior tracheal membrane and superior trachea Yes Yes Often present oncentric calcified or ossified nodular or concentric wall thickening without posterior sparing; may involve the larynx and upper trachea Yes Yes No Subglottic narrowing when focal; history of sinus or renal disease, pulmonary cavitary nodules, or pulmonary hemorrhage No No No Only diffuse tracheal abnormality resulting in both anteroposterior and lateral tracheal dilatation Yes Yes Yes Hilar and mediastinal lymphadenopathy; perilymphatic pulmonary nodules Inflammatory bowel disease Diffuse or focal tracheal narrowing Yes Yes No History of inflammatory bowel disease or chronic abdominal pain in men with chronic obstructive pulmonary disease [1]. The extrathoracic trachea has a normal shape. However, the intrathoracic trachea shows a marked decrease in coronal diameter and an associated increase in sagittal diameter without tracheal wall thickening (Fig. 4). This deformity of the trachea is believed to result from repeated injury to the intrathoracic trachea from chronic coughing. Initially, changes are noted at only the thoracic inlet but can involve the entire intrathoracic trachea over time. Other smoking-related conditions may be present such as emphysema, respiratory bronchiolitis, and lung cancer. Relapsing Polychondritis Relapsing polychondritis (RP) is an autoimmune disease that affects cartilaginous structures such as the nose, ear, and laryngotracheobronchial tree. irway involvement occurs in up to half of patients, with pneumonia being the most common cause of death [5]. On T, RP is characterized by increased attenuation and thickening of the anterior and JR:196, March 2011 W241

3 hung et al. Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with history of wheezing and shortness of breath. and, ontrast-enhanced chest T images show increased ratio of coronal-to-sagittal tracheal diameters (arrows). This finding is characteristic of lunate trachea in this patient with tracheomalacia. Fig. 1 Normal trachea., Diagram of normal trachea in axial plane shows discontinuity of posterior aspect of cartilaginous ring. Posterior wall of trachea is supported by trachealis muscle., xial T image of 55-year-old woman with normal trachea shows typical inverted U-shaped appearance of trachea. Fig year-old man with neck pain after selfinflicted head trauma., Unenhanced T image shows normal tracheal caliber in extrathoracic upper chest., T image shows severe collapse of intrathoracic trachea on expiration; this finding is highly suggestive of tracheomalacia., Difference in caliber of intrathoracic (thick white arrow) and extrathoracic (thin white arrow) trachea is illustrated on sagittal reformation. Incidental note is made of ossification (black arrows) of posterior longitudinal ligament. lateral walls of the large airways and concomitant destruction of the cartilaginous tracheobronchial rings with sparing of the posterior wall [6] (Fig. 5). Tracheomalacia and large airways stenosis may also be present. Tracheobronchopathia Osteochondroplastica Tracheobronchopathia osteochondroplastica is characterized by the development of osseous and cartilaginous nodules in the submucosa of the lower two thirds of the trachea and central bronchi. On T, nodules typically measuring 1 3 mm arise from the cartilaginous rings and protrude into the airway lumen; the location of these nodules is sometimes better depicted with virtual bronchoscopy. Tracheomalacia does not occur, although an association with sabersheath trachea has been described [7]. Similar W242 JR:196, March 2011

4 T of the Trachea and entral irways Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with long history of smoking and chronic cough. ontrast-enhanced T image shows increased anteroposterior-to-lateral dimensions of trachea (thick arrow) from smokingrelated chronic obstructive pulmonary disease. This finding is characteristic of saber-sheath trachea. Left upper lobe bronchogenic carcinoma (thin arrow) is present. to RP, the posterior walls of the trachea and bronchi are spared. However, the presence of focal coarse calcification and ossification (Fig. 6) is more typical of tracheobronchopathia osteochondroplastica than RP. myloidosis Tracheobronchial amyloidosis is the most common subtype of thoracic amyloidosis (Fig. 7). T shows diffuse nodular thickening of the trachea and main bronchi, often involving the subglottic trachea. ronchial stenosis or occlusion may result in lobar or segmental atelectasis [8]. Nodular calcified regions within the trachea are common, as in Fig year-old man with history of asthma presents with shortness of breath and cough., ontrast-enhanced T images of chest show smooth thickening (white arrows) of trachea with posterior sparing (black arrows); these findings are most consistent with relapsing polychondritis. tracheobronchopathia osteochondroplastica. myloidosis typically involves the airway concentrically, whereas tracheobronchopathia osteochondroplastica and RP characteristically spare the posterior tracheal and bronchial walls. In addition, amyloidosis may affect the larynx, pharynx, and superior trachea in contrast to tracheobronchopathia osteochondroplastica [9]. Wegener Granulomatosis Wegener granulomatosis is an idiopathic necrotizing granulomatous vasculitis that can affect patients of any age. The upper airways are almost always affected; the lungs and kidneys are involved in most patients (90% and 80%, respectively) [10]. Elevation of cytoplasmic antineutrophil antibodies against protease 3 in cytoplasmic granule titers is common and reflects disease activity. Fig year-old woman with chronic cough., Unenhanced T images show nodular, partially calcified, irregular thickening of trachea and main bronchi (arrows) with posterior sparing; these findings are consistent with tracheobronchopathia osteochondroplastica. JR:196, March 2011 W243

5 hung et al. Fig year-old woman with history of tracheal amyloidosis. and, xial () and coronal () contrast-enhanced T images of chest show diffuse circumferential thickening (arrows) of trachea. Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with chest pain and cough., ontrast-enhanced T image of lower neck shows circumferential soft-tissue thickening and smooth narrowing of subglottic trachea (arrow)., Three-dimensional reconstruction of trachea and proximal airways shows smooth narrowing of subglottic trachea (arrow)., T image obtained using lung window settings shows cavitary lesion in right upper lobe (arrow) in this patient with Wegener granulomatosis. On T, the trachea and main bronchi may be diffusely or focally circumferentially thickened; subglottic stenosis occurs in approximately 25% of patients and bronchial stenosis in about 18% of patients [11] (Fig. 8). Peripheral bronchial narrowing, lobar and segmental atelectasis, or bronchiectasis may also be present. oexistent pulmonary nodules and masses, which are sometimes cavitary; consolidation; and ground-glass opacities may suggest Wegener granulomatosis. Mounier-Kuhn Syndrome Mounier-Kuhn syndrome (tracheobronchomegaly) is unique among the diffuse tracheal diseases in that it is characterized by diffuse airway dilatation. Tracheobronchomegaly arises from either a congenital abnormality or atrophy of the connective tissue of the trachea and central bronchi. tracheal diameter of greater than 3 cm and mainstem bronchi diameters of greater than 2.4 cm are highly suggestive of Mounier-Kuhn syndrome [12, 13]. road diverticula may project between the cartilaginous rings, giving the trachea and proximal bronchi a corrugated appearance (Fig. 9). Mild tracheal dilatation W244 JR:196, March 2011

6 T of the Trachea and entral irways Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved may also occur in the setting of chronic obstructive pulmonary disease, although differentiation from Mounier-Kuhn syndrome is usually readily made. Sarcoidosis Sarcoidosis is an idiopathic systemic disease characterized by the formation of noncaseating hyalinizing granulomas in a variety of tissues including the lungs and airways. Hilar Fig year-old man with history of melanoma., ontrast-enhanced T image of chest shows diffuse dilatation of trachea., oronal reformation shows diffuse central bronchiectasis., Sagittal reformation shows tracheal corrugation (arrows). Overall, findings are consistent with Mounier-Kuhn syndrome. Fig year-old man with shortness of breath and history of sarcoidosis. and, ontrast-enhanced T images of chest show partially calcified, irregular, nodular thickening of trachea (arrows). Tracheal lumen is narrow and abnormal in shape. and mediastinal lymphadenopathy, lung nodules in a perilymphatic distribution, bronchovascular bundle thickening with or without fibrosis, and ground-glass opacities are common T manifestations of sarcoidosis. Large airway involvement, on the other hand, is very uncommon. irway abnormalities may result from extrinsic compression by adjacent diseased lymph nodes or from primary infiltration of the airway walls with noncaseating granulomas [6] (Fig. 10). Upper tracheal and laryngeal involvement is more common than distal central airway involvement [6]. Inflammatory owel Disease Tracheal or bronchial involvement in inflammatory bowel disease is uncommon, often occurring late in the course of disease. Pulmonary manifestations include bronchiectasis, chronic bronchitis, obliterative JR:196, March 2011 W245

7 hung et al. Downloaded from by on 02/15/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with history of rohn disease. and, Unenhanced T images of chest show circumferential, irregular thickening of trachea (arrows). Mid and lower tracheal lumen is mildly narrowed. bronchiolitis, interstitial fibrosis, and large airway disease [14]. Involvement of the large airways manifests on T as diffuse or focal large airway narrowing. The tracheal wall may be smoothly or irregularly thickened (Fig. 11). This diagnosis should be considered in those presenting with asthma-like symptoms with a history of inflammatory bowel disease or with chronic gastrointestinal complaints. FOR YOUR INFORMTION onclusions Traditionally, the trachea has been an afterthought on noninvasive imaging studies. MDT is the imaging test of choice to evaluate the trachea and central airways because of its high spatial resolution and ability to produce a variety of reformations. Furthermore, T can show abnormalities of the tracheal lumen, tracheal walls, and immediate surrounding tissues. dditionally, tracheal diseases may be misdiagnosed as asthma by the clinician. The radiologist is often the first to suggest the diagnosis of a diffuse tracheal disease and can often suggest a single diagnosis. In cases when the diagnosis is unclear, T can serve as a guide for bronchoscopic evaluation and transbronchial biopsy. This article is available for ME credit. See for more information. References 1. oiselle P. Imaging of the large airways. lin hest Med 2008; 29: Stern E, Graham, Webb W, Gamsu G. Normal trachea during forced expiration: dynamic T measurements. Radiology 1993; 187: oiselle P, O Donnell, ankier, et al. Tracheal collapsibility in healthy volunteers during forced expiration: assessment with multidetector T. Radiology 2009; 252: oiselle P, Ernst. Tracheal morphology in patients with tracheomalacia: prevalence of inspiratory lunate and expiratory frown shapes. J Thorac Imaging 2006; 21: Michet J, McKenna, Luthra H, O Fallon W. Relapsing polychondritis: survival and predictive role of early disease manifestations. nn Intern Med 1986; 104: Kwong JS, Müller NL, Miller RR. Diseases of the trachea and main-stem bronchi: correlation of T with pathologic findings. RadioGraphics 1992; 12: Restrepo S, Pandit M, Villamil M, Rojas I, Perez J, Gascue. Tracheobronchopathia osteochondroplastica: helical T findings in 4 cases. J Thorac Imaging 2004; 19: Prince J, Duhamel D, Levin D, Harrell J, Friedman P. Nonneoplastic lesions of the tracheobronchial wall: radiologic findings with bronchoscopic correlation. RadioGraphics 2002; 22[Spec No]: S215 S Gilad R, Milillo P, Som P. Severe diffuse systemic amyloidosis with involvement of the pharynx, larynx, and trachea: T and MR findings. JNR 2007; 28: nanthakrishnan L, Sharma N, Kanne J. Wegener s granulomatosis in the chest: high-resolution T findings. JR 2009; 192: Lohrmann, Uhl M, Kotter E, urger D, Ghanem N, Langer M. Pulmonary manifestations of Wegener granulomatosis: T findings in 57 patients and a review of the literature. Eur J Radiol 2005; 53: Webb EM, Elicker M, Webb WR. Using T to diagnose nonneoplastic tracheal abnormalities: appearance of the tracheal wall. JR 2000; 174: Marom E, Goodman P, Mcdams H. Diffuse abnormalities of the trachea and main bronchi. JR 2001; 176: Spira, Grossman R, alter M. Large airway disease associated with inflammatory bowel disease. hest 1998; 113: W246 JR:196, March 2011