(Radiographics. 2002;22:S215-S230.)
© RSNA, 2002
Nonneoplastic Lesions of the Tracheobronchial Wall: Radiologic Findings with Bronchoscopic Correlation1
Jeffrey S. Prince, MD,
David R. Duhamel, MD,
David L. Levin, MD, PhD,
James H. Harrell, MD and
Paul J. Friedman, MD
1 From the Department of Radiology (J.S.P., D.L.L., P.J.F.) and the Pulmonary Special Procedures Unit (D.R.D., J.H.H.), Division of Pulmonary and Critical Care Medicine, UCSD Medical Center, 200 W Arbor Dr, Mail Code 8756, San Diego, CA 92103-8756. Recipient of a Cum Laude award for an education exhibit at the 2001 RSNA scientific assembly. Received February 2, 2002; revision requested March 20 and received April 11; accepted April 18. Address correspondence to D.L.L. (e-mail: dlevin@ucsd.edu).
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Abstract
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Nonneoplastic diseases of the central airways are uncommon but can be categorized as either focal or diffuse, although there is some overlap. Focal diseases include postintubation stenosis, postinfectious stenosis, posttransplantation stenosis, and various systemic diseases that may involve the airways and lead to focal stenosis (eg, Crohn disease, sarcoidosis, Behçet syndrome). Diffuse diseases of the central airways include Wegener granulomatosis, relapsing polychondritis, tracheobronchopathia osteochondroplastica, amyloidosis, papillomatosis, and rhinoscleroma. Conventional radiography is often the first step in the evaluation of suspected central airway disease and may be adequate in itself to identify the abnormality. However, computed tomography (CT) improves both the detection and characterization of central airway disease. Bronchoscopy remains the primary procedure for the diagnostic work-up of these disease entities. Nevertheless, a thorough radiologic evaluation with radiography and CT may demonstrate specific imaging findings (eg, calcification) that can help narrow the differential diagnosis and aid in the planning of bronchoscopy or therapeutic intervention.
Index Terms: Amyloidosis, 671.68 • Bronchi, CT, 671.1211 • Bronchi, diseases, 671.319, 671.622, 671.68, 671.814 • Bronchography, 671.122 • Papilloma, 671.319 • Sarcoidosis, 671.622 • Trachea, CT, 671.1211 • Trachea, diseases, 671.319, 671.622, 671.68, 671.814 • Trachea, stenosis or obstruction, 671.225, 671.7522
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Evaluate tracheal diseases with conventional radiography and CT.
- Identify the imaging features of nonneoplastic diseases of the central airways to help narrow the differential diagnosis.
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Introduction
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Nonneoplastic diseases of the central airways are uncommon and may be infectious, postinfectious, posttraumatic, inflammatory, or idiopathic. These diseases are often categorized as either focal or diffuse, although some of them fit into both categories. In some cases, conventional radiography of the chest is adequate to identify the abnormality. However, diagnosis may be difficult with standard chest radiography because of poor imaging technique and an inadequate search. Computed tomography (CT) improves both the detection and characterization of central airway disease. Bronchoscopy, however, remains the primary procedure for the diagnostic work-up of these disease entities. By reviewing and correlating the radiographic and bronchoscopic appearances of these processes, we hope to provide a greater understanding of these diseases.
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Focal Diseases of the Central Airways
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Postintubation Stenosis
Stenosis of the trachea can be a complication of either endotracheal intubation or placement of the tracheostomy tube. The high pressure of an endotracheal tube balloon against the tracheal wall may result in mucosal necrosis. Infection, mechanical irritation, steroid administration, and positive pressure ventilation may further exacerbate this injury and lead to scarring and stenosis (1). The use of endotracheal tubes with low-pressure cuffs reduces the prevalence of stenosis to less than 1% from the 20% reported with high-pressure cuffs (1). With endotracheal tubes, the stenosis typically occurs in the subglottic region at the cuff site. In patients who have undergone tracheostomy, the postextubation stenosis typically occurs at the stoma site (2). Clinical presentation includes dyspnea at exertion, stridor, and wheezing (3). Tracheal laceration from either penetrating or blunt injury may also result in stenosis as a late complication secondary to fibrosis or granulation tissue at the site of injury. The radiographic and bronchoscopic appearances are similar to those of postintubation stenosis.
The typical radiographic finding is a symmetric narrowing less than 2 cm in length with an hourglass shape (Fig 1a, 1b). Eccentric stenoses are less common (1). Tracheal stenosis is frequently overlooked at conventional radiography because it is often at the upper edge of the image. CT, especially with coronal reconstruction, better demonstrates the severity and extent of the stenosis and its relationship to the glottis (4).
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Figure 1a. Postintubation stenosis. (a, b) Conventional radiographs obtained in a 42-year-old man (a) and a 70-year-old woman (b) demonstrate focal subglottic stenosis (arrow) that resulted from prolonged intubation. (c) Corresponding bronchoscopic image obtained in the same patient as in b shows marked subglottic narrowing.
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Figure 1b. Postintubation stenosis. (a, b) Conventional radiographs obtained in a 42-year-old man (a) and a 70-year-old woman (b) demonstrate focal subglottic stenosis (arrow) that resulted from prolonged intubation. (c) Corresponding bronchoscopic image obtained in the same patient as in b shows marked subglottic narrowing.
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Figure 1c. Postintubation stenosis. (a, b) Conventional radiographs obtained in a 42-year-old man (a) and a 70-year-old woman (b) demonstrate focal subglottic stenosis (arrow) that resulted from prolonged intubation. (c) Corresponding bronchoscopic image obtained in the same patient as in b shows marked subglottic narrowing.
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Bronchoscopic evaluation typically shows one of three findings: a circumferential luminal narrowing less than 2 cm in length (Fig 1c), a thin membrane that projects into the lumen, or a long segment of eccentric soft-tissue thickening (2,5). Rigid bronchoscopy with mechanical dilation or neodymium yttrium aluminum garnet (Nd:YAG) laser therapy has been used to successfully treat the stenosis. However, if the lesion is complex, lengthy, or fibrous, surgical resection and reconstruction may be required (3,5).
Postinfectious Stenosis
Tuberculous stenosis is an endobronchial complication of pulmonary tuberculosis that can develop acutely at the time of infection or can become manifest as many as 30 years later. Endobronchial tuberculosis has been reported in 10%–37% of patients with pulmonary parenchymal tuberculosis. Some degree of stenosis may develop in up to 90% of patients with endobronchial tuberculosis, despite appropriate antituberculous therapy (6–9). However, active parenchymal tuberculosis is not a prerequisite to the development of tracheobronchial stenosis. Tuberculous strictures are more frequently seen in Asian and African populations, among whom the prevalence of tuberculosis is greater. In addition, tuberculous stenoses may become symptomatic more frequently in Asian women because the normal tracheal diameter is smaller in that population (7). Stenoses may follow granulomatous infection or fungal infection.
Postinfectious strictures are characteristically cicatricial and extensive. Involvement at multiple sites within the tracheobronchial tree is common. The mucosa between strictures may be completely normal. Most stenoses are believed to be due to infectious necrosis and ulceration of the bronchial mucosa that leads to formation of granulation tissue and fibrotic stenosis. Up to 20% of stenoses, however, are associated with extrinsic compression of the bronchus by lymph nodes (7). Mediastinal fibrosis, an uncommon complication of infection, especially that due to histoplasmosis, may result in multifocal narrowing of the trachea.
Radiographic findings in postinfectious stenosis include focal narrowing of the trachea or bronchi (Figs 2a, 3a, 3b). Calcification of the stenotic region is rare. The changes typical of posttuberculous fibrocavitary parenchymal disease may be seen. Segmental or lobar atelectasis is a common feature. CT may show lymphadenopathy and parenchymal inflammatory changes in addition to airway narrowing (Fig 2b). In patients with tuberculous stenosis, the CT manifestations of active and fibrotic disease are different (10): In active disease, the airway walls are typically thickened and irregular, whereas in fibrotic disease, the walls are smooth and thin-walled.
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Figure 2a. Posttuberculous stenosis in a 24-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a focal stricture (arrow) at the proximal left main bronchus beginning just distal to the carina. The remainder of the bronchus is also narrowed and irregular. Volume has been lost from the left lower lobe. (c) Bronchoscopic image also shows the focal stenosis (arrow).
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Figure 2b. Posttuberculous stenosis in a 24-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a focal stricture (arrow) at the proximal left main bronchus beginning just distal to the carina. The remainder of the bronchus is also narrowed and irregular. Volume has been lost from the left lower lobe. (c) Bronchoscopic image also shows the focal stenosis (arrow).
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Figure 2c. Posttuberculous stenosis in a 24-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a focal stricture (arrow) at the proximal left main bronchus beginning just distal to the carina. The remainder of the bronchus is also narrowed and irregular. Volume has been lost from the left lower lobe. (c) Bronchoscopic image also shows the focal stenosis (arrow).
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Figure 3a. Postinflammatory stenosis due to Coccidioides infection in a 35-year-old man. (a) Conventional radiograph shows a long segment of narrowing that involves the left main bronchus (arrowheads). (b) Bronchoscopic image shows a stricture at the origin of the left main bronchus (arrow).
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Figure 3b. Postinflammatory stenosis due to Coccidioides infection in a 35-year-old man. (a) Conventional radiograph shows a long segment of narrowing that involves the left main bronchus (arrowheads). (b) Bronchoscopic image shows a stricture at the origin of the left main bronchus (arrow).
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At bronchoscopy, the typical finding is localized endobronchial gelatinous granulation tissue. The mucosa may be red, nodular, and ulcerated, and the diagnosis of bronchogenic cancer must be considered until microbiologic studies are completed (Figs 2c, 3b).
The primary treatment for tuberculous stenosis due to active disease includes antituberculous chemotherapy, sometimes combined with steroids. However, once fibrotic stenosis occurs, medical therapy alone is rarely useful and more aggressive intervention is required. Balloon dilation and mechanical dilation with the rigid bronchoscope are useful endoscopic techniques for the treatment of bronchial stenosis. The rate of recurrence of the stenosis is high, and multiple dilations are frequently required. Once the stenosis is sufficiently dilated, a silastic endobronchial stent (Bryan, Woburn, Mass) can be deployed to help maintain long-term patency. Surgery, either segmental resection of the bronchus or lobar resection, may be necessary for lesions if endoscopic therapy has failed.
Posttransplantation Stenosis
Bronchial stenosis after lung transplantation reflects abnormal healing of the anastomosis. In the past, airway complications were seen in approximately 50% of patients (11). The bronchial arterial supply of the transplanted lung is not routinely restored during surgery, and the transplanted bronchus is dependent on low-pressure retrograde perfusion from pulmonary arterial collateral vessels immediately after surgery. Infection, rejection, and immunosuppression may also contribute to airway complications. Improved surgical techniques such as overlapping of the bronchial stump, moderation in the use of steroids, and increased use of cyclosporine have resulted in fewer airway complications. Current data show that the risk of anastomotic complications ranges from 12% to 17% (12,13). Clinical manifestations of anastomotic complications include failure of improvement in symptoms during the months after transplantation and decline in flow rates (forced expiratory volume in 1 second).
At radiography, posttransplantation stricture is characterized by narrowing at the bronchial anastomotic site. This narrowing is seen best with CT (Fig 4a), preferably with the use of thin collimation. Extraluminal gas and mucosal ulcerations are signs of anastomotic dehiscence that occur in the early postoperative period (13). Virtual bronchoscopy has been shown to depict over 90% of stenoses found at fiberoptic bronchoscopy (14).
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Figure 4a. Posttransplantation stenosis in a 45-year-old woman who had undergone bilateral lung transplantation. (a) CT scan shows a focal stenosis at the anastomotic site within the right lung. (b) Bronchoscopic image shows granulation tissue and narrowing as well as suture material (arrowheads).
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Figure 4b. Posttransplantation stenosis in a 45-year-old woman who had undergone bilateral lung transplantation. (a) CT scan shows a focal stenosis at the anastomotic site within the right lung. (b) Bronchoscopic image shows granulation tissue and narrowing as well as suture material (arrowheads).
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Bronchoscopy remains the standard for evaluation. The typical appearance is a fibrotic, focal, cicatricial narrowing at the anastomotic site. Granulation tissue may surround suture material (Fig 4b). Treatment consists of balloon dilation with placement of a polymeric silicone stent. The stenosis typically responds well to therapy, and the stent can be removed after 1–2 years.
Miscellaneous Focal Stenoses
A number of systemic diseases can involve the airways and lead to focal stenosis of the trachea and proximal bronchi.
Crohn Disease.—
Crohn disease is a chronic inflammatory disease of the terminal ileum that may involve any segment of the gastrointestinal tract. Rare involvement of the respiratory tract has also been described (15,16). Case reports have demonstrated involvement of the larynx and the subglottic trachea. Airway obstruction can result either directly from submucosal edema and chronic inflammation or indirectly from inflammation of the cricoarytenoid joint. In the majority of reported cases, the initial manifestation of Crohn disease has been within the gastrointestinal tract, with respiratory involvement being a late manifestation.
Radiographic manifestations include edema of the epiglottis, aryepiglottic folds, and arytenoids; tracheal deformity; bronchial thickening with mucoid impaction; and diffuse soft-tissue swelling of the hypopharynx and larynx. Focal narrowing of the airway may be present (Fig 5a, 5b).
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Figure 5a. Crohn disease in a 39-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a long segment of irregular narrowing (arrow) that primarily involves the proximal left main bronchus. (c) Bronchoscopic image shows mucosal edema and granulation tissue with endobronchial obstruction.
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Figure 5b. Crohn disease in a 39-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a long segment of irregular narrowing (arrow) that primarily involves the proximal left main bronchus. (c) Bronchoscopic image shows mucosal edema and granulation tissue with endobronchial obstruction.
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Figure 5c. Crohn disease in a 39-year-old woman. (a, b) Conventional radiograph (a) and CT scan (b) show a long segment of irregular narrowing (arrow) that primarily involves the proximal left main bronchus. (c) Bronchoscopic image shows mucosal edema and granulation tissue with endobronchial obstruction.
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Presenting symptoms include stridor, dyspnea, dysphagia, productive cough, and hoarseness. Bronchoscopic findings (Fig 5c) include epiglottic and arytenoid edema, subglottic stenosis, and inflammation and ulceration of the tracheobronchial mucosa with endobronchial obstruction (15–17).
Sarcoidosis.—
Sarcoidosis typically affects the hilar and mediastinal lymph nodes and the lung parenchyma. However, 1%–3% of patients will have tracheal involvement, primarily in the upper part of the trachea (18). The distal part of the trachea and primary bronchi are affected infrequently. Narrowing of the airway may be secondary to extrinsic compression from enlarged lymph nodes (Fig 6a) or may be the result of granuloma formation within the airway mucosa and submucosa (18).
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Figure 6a. Sarcoidosis in a 37-year-old man. (a) CT scan shows marked narrowing of the bronchus intermedius (arrow) by an adjacent nodal mass. Densely calcified nodes are seen within the right hilum (arrowhead). (b) Bronchoscopic image shows mucosal inflammation in addition to focal stenosis.
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Figure 6b. Sarcoidosis in a 37-year-old man. (a) CT scan shows marked narrowing of the bronchus intermedius (arrow) by an adjacent nodal mass. Densely calcified nodes are seen within the right hilum (arrowhead). (b) Bronchoscopic image shows mucosal inflammation in addition to focal stenosis.
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The radiographic appearance is similar to that of other stenoses. Airway granuloma formation may result in an apparent thickening of the mucosa. Other findings, such as lymph node enlargement, may also be present (18,19). The classic endobronchial finding is a raised "cobblestone" appearance of the mucosa (Fig 6b). Whitish granulomatous material may be seen in stenotic regions.
Behçet Syndrome.—
Behçet syndrome is a systemic vasculitis that leads to ulcerating mucosal lesions of the gastrointestinal tract. Pulmonary involvement, which is present in only about 5% of patients, manifests primarily as focal parenchymal areas of increased opacity at chest radiography. Ulcerative lesions may be found in the trachea and proximal airways. Mucosal edema may result in irregular narrowing of the airway (Fig 7) (20).
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Figure 7a. Behçet syndrome in a 36-year-old man. (a) Conventional radiograph shows a long segment of stenosis within the left main bronchus (arrowheads) that begins just distal to the carina. Volume loss within the left lung is significant. (b) Bronchoscopic image shows stenosis of the left main bronchus (arrow).
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Figure 7b. Behçet syndrome in a 36-year-old man. (a) Conventional radiograph shows a long segment of stenosis within the left main bronchus (arrowheads) that begins just distal to the carina. Volume loss within the left lung is significant. (b) Bronchoscopic image shows stenosis of the left main bronchus (arrow).
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Diffuse Diseases of the Central Airways
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Wegener Granulomatosis
A disease of unknown pathogenesis, Wegener granulomatosis is characterized by a necrotizing granulomatous vasculitis that is capable of affecting all organs but has a predilection for the upperand lower respiratory tracts (21). It is more prevalent in men and typically affects middle-aged persons. The classic manifestation includes glomerulonephritis in addition to systemic vasculitis. Liebow described an entity called limited Wegener granulomatosis (22), which has the typical clinical and histopathologic features of the disease within the lungs and lower respiratory tract without renal or upper airway involvement. Laryngeal and endobronchial involvement occurs most often as a late complication of classic Wegener granulomatosis. Rare cases of isolated involvement of the subglottic space or tracheobronchial tree have been reported (23).
The radiographic features of airway involvement may be focal or diffuse. The diseased portions of the trachea typically have circumferential mucosal thickening, irregularity, and ulceration that are best shown with CT (Fig 8) (21,24). Involvement of the cartilaginous rings is less common but may result in deformity and narrowing of the trachea (25). Bronchial wall involvement may lead to airway obstruction and atelectasis. Other radiographic findings include parenchymal nodular areas of increased opacity, which may cavitate; ill-defined airspace areas of increased opacity; and pleural effusions (21).
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Figure 8a. Wegener granulomatosis. (a) Chest radiograph obtained in a 27-year-old woman shows a long segment of narrowing that extends from the subglottic space to the thoracic inlet. (b) CT scan obtained in a 55-year-old woman shows circumferential thickening of the tracheal mucosa. (c) Bronchoscopic image obtained in the same patient as in a shows subglottic stenosis and irregular mucosal thickening.
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Figure 8b. Wegener granulomatosis. (a) Chest radiograph obtained in a 27-year-old woman shows a long segment of narrowing that extends from the subglottic space to the thoracic inlet. (b) CT scan obtained in a 55-year-old woman shows circumferential thickening of the tracheal mucosa. (c) Bronchoscopic image obtained in the same patient as in a shows subglottic stenosis and irregular mucosal thickening.
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Figure 8c. Wegener granulomatosis. (a) Chest radiograph obtained in a 27-year-old woman shows a long segment of narrowing that extends from the subglottic space to the thoracic inlet. (b) CT scan obtained in a 55-year-old woman shows circumferential thickening of the tracheal mucosa. (c) Bronchoscopic image obtained in the same patient as in a shows subglottic stenosis and irregular mucosal thickening.
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The bronchoscopic findings in patients with Wegener granulomatosis are variable. Cordier et al (21) reported that 55% of their patients with parenchymal involvement from Wegener granulomatosis had bronchoscopic abnormalities. Subglottic stenosis is found in up to 16% of cases. Inflammatory ulcers are the most common finding (26). On occasion, a yellow-green plaque is found endobronchially. This finding correlates with active disease and an increased rate of diagnostic biopsy. Obstructive endobronchial pseudotumors of inflammatory granulomatous tissue have been reported. Other bronchoscopic findings include isolated lobar hemorrhage or purulent secretions. Cicatricial tracheal or bronchial stenosis occurs much less frequently (21,26).
Sometimes the diagnosis of Wegener granulomatosis is difficult. Biopsy specimens from the upper respiratory tract have a notoriously low yield when the strict pathologic criterion of vasculitis is required (25). The c–antineutrophil cytoplasmic antibody is a fairly specific test for Wegener granulomatosis; however, in a series of patients with endobronchial involvement studied by Daum et al (26), the test was found not to be predictive of disease presence or activity. Although isolated Wegener granulomatosis of the larynx and tracheobronchial tree is unusual, the literature suggests that early treatment of active lesions with corticosteroids and cyclophosphamide is warranted (27).
Relapsing Polychondritis
Relapsing polychondritis is a rare, autoimmune syndrome characterized by recurrent episodes of cartilaginous inflammation with subsequent degeneration, loss of structure, and fibrosis. Cartilaginous destruction of the ear, nose, peripheral joints, larynx, and tracheobronchial tree may develop as a result of this process (28). Laryngotracheobronchial involvement is seen at presentation in only 10% of cases, but it will eventually develop in half of all patients (21,27). Involvement of the respiratory tract carries a poor prognosis (29). The disease affects men and women equally, but airway involvement is more common in women. Peak prevalence occurs between 40 and 60 years of age. It predominantly affects Caucasians but has been reported in people of other races and ethnic origins. It is considered an autoimmune process, and autoantibodies have been found directed against cartilage and type II collagen. The diagnosis can be made on clinical grounds when three or more of the following features are present: bilateral auricular chondritis, nonerosive seronegative inflammatory polyarthritis, nasal chondritis, ocular inflammation, respiratory tract chondritis, and audiovestibular damage (29).
At radiography, diffuse or localized airway involvement may be seen (Fig 9a). The larynx and upper trachea are affected most frequently, but the disease may involve airways to the subsegmental level (28). Thickening of the tracheal wall with destruction of the cartilaginous rings is characteristic. Sparing of the posterior membrane of the trachea helps to differentiate polychondritis from other diseases (18). Dynamic imaging during expiration may demonstrate airway collapse (Fig 9b).
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Figure 9a. Relapsing polychondritis. (a) Conventional radiograph obtained in a 75-year-old woman shows a long segment of tracheal narrowing and irregularity. (b) End-inspiration and end-expiration CT scans obtained in a 64-year-old man show dynamic collapse of the trachea with expiration (right). Calcification and thickening of the cartilaginous portions of the trachea (arrow) with sparing of the posterior wall (arrowhead) are also seen. (c) Bronchoscopic image obtained in the same patient as in a shows diffuse mucosal edema with dynamic airway collapse.
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Figure 9b. Relapsing polychondritis. (a) Conventional radiograph obtained in a 75-year-old woman shows a long segment of tracheal narrowing and irregularity. (b) End-inspiration and end-expiration CT scans obtained in a 64-year-old man show dynamic collapse of the trachea with expiration (right). Calcification and thickening of the cartilaginous portions of the trachea (arrow) with sparing of the posterior wall (arrowhead) are also seen. (c) Bronchoscopic image obtained in the same patient as in a shows diffuse mucosal edema with dynamic airway collapse.
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Figure 9c. Relapsing polychondritis. (a) Conventional radiograph obtained in a 75-year-old woman shows a long segment of tracheal narrowing and irregularity. (b) End-inspiration and end-expiration CT scans obtained in a 64-year-old man show dynamic collapse of the trachea with expiration (right). Calcification and thickening of the cartilaginous portions of the trachea (arrow) with sparing of the posterior wall (arrowhead) are also seen. (c) Bronchoscopic image obtained in the same patient as in a shows diffuse mucosal edema with dynamic airway collapse.
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The bronchoscopic findings include diffuse airway narrowing from mucosal edema and erythema. Tracheobronchomalacia may be seen with resultant airway collapse (Fig 9c). Fixed narrowing and stenosis may develop from granulation tissue and peribronchial fibrosis (30).
Approaches to treatment are varied. In disease limited to the larynx and upper trachea, a tracheostomy may be performed. Other invasive techniques include placement of endobronchial polymeric silicone stents to help maintain airway patency. Surgical resection is of limited value in the treatment of inflammatory lesions, but it may have a role in isolated fixed stenosis. The mainstay of treatment remains medical management with corticosteroids. Patients with mild disease have undergone successful treatment with a combination of nonsteroidal anti-inflammatory drugs and dapsone. Success has also been reported with immunosuppressive drugs such as azathioprine and cyclosporine (30).
Tracheobronchopathia Osteochondroplastica
Tracheobronchopathia osteochondroplastica is an idiopathic benign disease of the trachea and major bronchi characterized by multiple submucosal osteocartilaginous nodules. The nodules classically affect the lower two-thirds of the trachea and proximal portions of the primary bronchi (31). The nodules may be either focal or diffuse. There is a 3:1 male predilection, and the disease typically manifests in patients in their mid-50s. The prevalence of tracheobronchopathia osteochondroplastica found during routine bronchoscopy for unrelated complaints ranges from 0.02% (32) to 0.7% (33). Frequently, however, the diagnosis is made after a difficult intubation or during bronchoscopy. Many experienced bronchoscopists believe the disease occurs more often but is not recognized owing to its indolent course (34). Most patients are asymptomatic, but presentation may include cough, dyspnea at exertion, recurrent infection, wheezing, and, on occasion, hemoptysis. The latter symptom occurs when opposing nodules rub against each other, causing erosion of the mucosa and subsequent bleeding. At histopathologic examination, the nodules are submucosal osteocartilaginous growths. The mucosal surface is typically intact, and a connection to the perichondrium of a tracheal ring is frequently seen (18).
In moderate to severe disease, conventional radiography may reveal tracheal scalloping and nodular irregularity or irregular asymmetric stenosis (Fig 10a) (31). Thickened tracheal cartilage with irregular calcification is seen with CT (Fig 10b). Multiple nodules, with or without calcification, may project into the airway lumen. The nodules of tracheobronchopathia osteochondroplastica spare the posterior membrane (18,31).
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Figure 10a. Tracheobronchopathia osteochondroplastica in a 36-year-old woman. (a) Conventional radiograph shows irregularity and narrowing over a long segment of the trachea. (b) CT scan of the middle part of the trachea shows irregular narrowing of the airway with calcification of the lateral walls. (c) Bronchoscopic image shows multiple osteocartilaginous nodules.
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Figure 10b. Tracheobronchopathia osteochondroplastica in a 36-year-old woman. (a) Conventional radiograph shows irregularity and narrowing over a long segment of the trachea. (b) CT scan of the middle part of the trachea shows irregular narrowing of the airway with calcification of the lateral walls. (c) Bronchoscopic image shows multiple osteocartilaginous nodules.
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Figure 10c. Tracheobronchopathia osteochondroplastica in a 36-year-old woman. (a) Conventional radiograph shows irregularity and narrowing over a long segment of the trachea. (b) CT scan of the middle part of the trachea shows irregular narrowing of the airway with calcification of the lateral walls. (c) Bronchoscopic image shows multiple osteocartilaginous nodules.
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The typical bronchoscopic appearance is of multiple smooth, raised, white, osteocartilaginous nodules, often described as "beaded" (Fig 10c) (28). These nodules are typically distributed over the anterolateral walls in association with the cartilaginous rings, sparing the posterior membrane. These lesions are typically hard, and biopsy of them is difficult. The diagnosis is often made from the visual appearance alone. There is currently no specific treatment to remove the abnormal tissue growth or to prevent the development of new nodules.
Amyloidosis
Amyloidosis is characterized by the deposition of abnormal proteinaceous material (amyloid) in extracellular tissue. It can be idiopathic or associated with various inflammatory, hereditary, or neoplastic pathogeneses. Pulmonary amyloidosis may be part of a widespread process that involves many organs or may be localized to the airways and lung parenchyma. It can occur in three forms: diffuse interstitial deposits, single or multiple pulmonary nodules, and, most commonly, submucosal tracheobronchial deposits (35). Primary pulmonary amyloidosis is relatively uncommon and refers to amyloidosis that is confined to the lung parenchyma, thereby excluding systemic amyloidosis.
The classic radiographic appearance of tracheobronchial disease is nodular and irregular narrowing of the tracheal lumen (Fig 11a) (18). Lobar or segmental collapse may be seen with endobronchial obstruction due to amyloid deposition. In certain cases of diffuse involvement, there is a significant component of calcification and ossification of the lesions. This finding leads to a second diagnosis of tracheopathia osteoplastica (36). In cases with the presence of calcification, differentiation is made on the basis of posterior membrane involvement (Fig 11b). Radiographic findings are normal in roughly one-fourth of cases (37).
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Figure 11a. Tracheobronchial amyloidosis in a 51-year-old woman. (a) Conventional radiograph shows irregular narrowing of the trachea over a long segment. (b) CT scan shows mucosal thickening with irregular calcification that involves the posterior membrane. (c) Bronchoscopic image shows diffuse nodular deposits that involve all portions of the trachea.
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Figure 11b. Tracheobronchial amyloidosis in a 51-year-old woman. (a) Conventional radiograph shows irregular narrowing of the trachea over a long segment. (b) CT scan shows mucosal thickening with irregular calcification that involves the posterior membrane. (c) Bronchoscopic image shows diffuse nodular deposits that involve all portions of the trachea.
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Figure 11c. Tracheobronchial amyloidosis in a 51-year-old woman. (a) Conventional radiograph shows irregular narrowing of the trachea over a long segment. (b) CT scan shows mucosal thickening with irregular calcification that involves the posterior membrane. (c) Bronchoscopic image shows diffuse nodular deposits that involve all portions of the trachea.
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Bronchoscopic findings may include multifocal flat plaques of gray-white amyloid material distributed throughout the trachea and bronchial lumina (Fig 11c). The entire endobronchial lumen may be involved, and there is no sparing of the posterior membrane as seen in tracheopathia osteoplastica (35). Less often, a raised, tumorlike mass of amyloid material (amyloid pseudotumor) can be seen and may be mistaken for a neoplasm (38). Although bronchoscopic biopsy is the mainstay of diagnosis, there is concern about an increased risk of bleeding because the amyloid deposits within the vascular wall may inhibit hemostasis. Management options are fairly limited. Endobronchial resection of obstructive lesions with the Nd:YAG laser has had some success, and there are reports of surgical treatments, including pneumonectomy (39). An option that appears promising is the placement of an endobronchial silicone stent to help maintain airway patency. Some clinicians have advocated the use of radiation therapy for diffuse or multifocal tracheobronchial involvement (37).
Papillomatosis
Papillomatosis results from infection of the upper respiratory tract by the human papillomavirus. This disease entity is most common in children but may also occur in adults. Infection occurs most frequently at the time of birth, when the child passes through an infected birth canal. Infection may also occur later in life, possibly through oral contact with infected external genitalia. Laryngeal papillomas are the most common manifestation. Multifocal infection, or aspiration of infected tissue from laryngeal papillomas distally, may lead to infection of the trachea, the bronchi, or even the alveoli. Involvement of the central airways occurs in 5% of patients with laryngeal papillomas, and small airway or alveolar involvement occurs in less than 1%. Papillomas may be single or multiple (40). Although the papillomas represent growth of new tissue, tracheolaryngeal papillomatosis is most frequently categorized as a nonneoplastic disease.
Radiographic findings include nodular narrowing of the airway that may be either focal or diffuse (Fig 12a). Nodules arise from the mucosal surface, and their intraluminal extent is better evaluated with CT (Fig 12b). Airway obstruction may lead to atelectasis, air trapping, postobstructive infection, or bronchiectasis. Distal spread may lead to parenchymal nodules that usually cavitate (18,19,40).
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Figure 12a. Papillomatosis. (a) Conventional radiograph obtained in a 31-year-old man shows irregular narrowing throughout the trachea. (b) CT scan obtained in a 30-year-old man shows multiple nodules that project into the tracheal lumen. Multiple parenchymal papillomas are also present. (c) Bronchoscopic image obtained in the same patient as in b shows multiple polypoid lesions within the trachea.
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Figure 12b. Papillomatosis. (a) Conventional radiograph obtained in a 31-year-old man shows irregular narrowing throughout the trachea. (b) CT scan obtained in a 30-year-old man shows multiple nodules that project into the tracheal lumen. Multiple parenchymal papillomas are also present. (c) Bronchoscopic image obtained in the same patient as in b shows multiple polypoid lesions within the trachea.
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Figure 12c. Papillomatosis. (a) Conventional radiograph obtained in a 31-year-old man shows irregular narrowing throughout the trachea. (b) CT scan obtained in a 30-year-old man shows multiple nodules that project into the tracheal lumen. Multiple parenchymal papillomas are also present. (c) Bronchoscopic image obtained in the same patient as in b shows multiple polypoid lesions within the trachea.
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At bronchoscopy, the papillomas are white and polypoid in appearance and may involve the larynx, trachea, or bronchi (Fig 12c). Laser treatment has been used; however, recurrence of the papillomas is common. In our practice, these patients undergo frequent surveillance bronchoscopy because recurrent therapy typically is required. Antiviral treatment has also been used. Malignant degeneration to squamous cell carcinoma is reported to occur in approximately 10% of adult cases (19). Any new or enlarging nodule identified radiographically should be evaluated further to exclude malignancy.
Rhinoscleroma
Rhinoscleroma is a chronic, progressive, granulomatous infection that affects the respiratory tract from the nose to the bronchi. The etiologic agent is a gram-negative diplobacillus, Klebsiella rhinoscleromatis (41). The disease initially involves nasal mucosa but may progress to any part of the airway. Laryngeal involvement is reported in 15%–80% of cases, but tracheobronchial disease is far less common (42). Rhinoscleroma is not highly contagious. Poor hygiene, prolonged close contact, and malnutrition increase the potential for infection and transmission (43). Death from rhinoscleroma is extremely rare and classically occurs in patients diagnosed in the late stages of the disease (44).
Untreated rhinoscleroma tends to progress slowly over many years, characterized by periods of remission and relapse. The disease manifests in four overlapping stages: the catarrhal stage, characterized by prolonged purulent rhinorrhea; the atrophic stage, with mucosal changes and crust formation; the granulomatous stage, characterized by granulomatous nodules in the nose with or without involvement of other parts of the respiratory tract; and the sclerotic stage, with dense cicatricial fibrosis of the involved tissue (45).
The radiographic findings include thickening of the tracheal wall (Fig 13a), nodular deformity of the tracheal mucosa, subglottic stricture, and concentric narrowing of the trachea and central bronchi (19). These regions of narrowing may be focal or diffuse and are of soft-tissue density without calcification.
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Figure 13a. Rhinoscleroma. (a) CT scan obtained in a 19-year-old woman shows circumferential thickening of the trachea. (b) Bronchoscopic image obtained in a 33-year-old woman shows multiple white-green plaques and mucosal edema.
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Figure 13b. Rhinoscleroma. (a) CT scan obtained in a 19-year-old woman shows circumferential thickening of the trachea. (b) Bronchoscopic image obtained in a 33-year-old woman shows multiple white-green plaques and mucosal edema.
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The bronchoscopic findings are variable (42). During the earlier stages of the disease, adherent white-green plaques may be seen in the airway (Fig 13b). Culture of this material will have a high yield of the organism. A positive culture of K rhinoscleromatis is diagnostic for the disease but occurs in less than 60% of cases (46). Immunocytochemical examination performed with antibodies to the O2K3 K antigen on K rhinoscleromatis can be used to make a definitive diagnosis. In the late stages of the disease, bland, densely fibrotic areas of scarring and stenosis may be seen focally or diffusely.
Antimicrobial therapy remains the cornerstone of therapy. Tetracycline or fluoroquinolone agents are recommended for a 6-month period or until results of nasal biopsies are negative. Balloon dilation or mechanical dilation can sometimes be used to treat significant fibrotic stenosis of the trachea and bronchus with the rigid bronchoscope. A tracheostomy is occasionally required for severe involvement of the larynx or subglottic space.
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Conclusions
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Radiography is often the first step in the evaluation of suspected disease of the central airways and remains an important adjunct to bronchoscopy. Conventional radiography and CT may help localize the disease and help characterize it as either focal or diffuse. A thorough radiologic evaluation may demonstrate specific imaging findings such as calcification that might help narrow the differential diagnosis. In addition, such details provide important information to aid in the planning of bronchoscopy and of any therapeutic intervention that may be considered.
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Footnotes
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Abbreviation: Nd:YAG = neodymium yttrium aluminum garnet
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Abstract
LEARNING OBJECTIVES
