(Radiographics. 2002;22:S199-S213.)
© RSNA, 2002
Broncholithiasis: Review of the Causes with Radiologic-Pathologic Correlation1
Joon Beom Seo, MD,
Koun-Sik Song, MD,
Jin Seong Lee, MD,
Jin Mo Goo, MD,
Hyae Young Kim, MD,
Jae-Woo Song, MD,
In Sun Lee, MD and
Tae-Hwan Lim, MD
1 From the Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea (J.B.S., K.S.S., J.S.L., I.S.L., T.H.L.); Department of Radiology, Seoul National University College of Medicine, Seoul, Korea (J.M.G.); Institute of Radiation Medicine, SNUMRC, Seoul, Korea (J.M.G.); Department of Radiology, National Cancer Center, Seoul, Korea (H.Y.K.); and Department of Radiology, Seoul Municipal Boramae Hospital, Seoul National University College of Medicine, Seoul, Korea (J.W.S.). Presented as an education exhibit at the 2001 RSNA scientific assembly. Received January 31, 2002; revision requested March 19 and received May 1; accepted May 21. Address correspondence to J.B.S. (e-mail: seojb@www.amc.seoul.kr).
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Abstract
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Broncholithiasis is defined as a condition in which calcified or ossified material is present within the bronchial lumen. Radiographic findings of broncholithiasis include airway obstruction such as atelectasis, mucoid impaction, bronchiectasis, and expiratory air trapping. Broncholithiasis is strongly suggested at computed tomography (CT) when an endobronchial or peribronchial calcified nodule is associated with findings of bronchial obstruction. Volume data acquisition by means of helical CT with sections less than 3 mm in thickness and multiplanar reformation along the bronchial tree are helpful in confirming the endobronchial location of the calcified material. The most common cause of broncholithiasis is erosion by and extrusion of a calcified adjacent lymph node into the bronchial lumen, a finding usually associated with tuberculosis or histoplasmosis. Other causes of broncholithiasis include (a) aspiration of bone tissue or in situ calcification of aspirated foreign material and (b) erosion by and extrusion of calcified or ossified bronchial cartilage plates. Primary endobronchial infections with dystrophic calcification, calcified endobronchial tumors, tracheobronchial diseases with mural calcification, and hypertrophied bronchial artery with intramural protrusion may mimic broncholithiasis. An awareness of the typical imaging findings of broncholithiasis, along with a knowledge of its various causes, help in establishing an accurate diagnosis to ensure proper case management.
© RSNA, 2002
Index Terms: Bronchi, stenosis or obstruction, 671.749 • Foreign bodies, in air and food passages, 60.811 • Lung, collapse, 60.749 • Lymphatic system, calcification, 996.816
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LEARNING OBJECTIVES FOR TEST 6
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After reading this article and taking the test, the reader will be able to:
- Recognize the radiologic features of broncholithiasis.
- Identify various causes of broncholithiasis and its mimics.
- Correlate the imaging features of broncholithiasis with bronchoscopic and pathologic findings.
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Introduction
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The term broncholithiasis is used to denote the presence of calcified or ossified material within the lumen of the bronchus (1). A broncholith is usually formed by erosion by and extrusion of a calcified adjacent lymph node into the bronchial lumen and is usually associated with long-standing foci of necrotizing granulomatous lymphadenitis (Fig 1). Other causes of broncholithiasis include (a) aspiration of bone tissue or in situ calcification of aspirated foreign material; (b) erosion by and extrusion of calcified or ossified bronchial cartilage plates; and (c) migration to a bronchus of calcified material from a distant site, such as a pleural plaque or the kidney (via a nephrobronchial fistula) (1). Some authors expanded the definition to include those cases in which peribronchial calcified lymph nodes distort the bronchial tree without extrusion of the lymph node into the bronchus (2,3).
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Figure 1a. Broncholithiasis due to extrusion of a calcified lymph node in a 41-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows an irregular calcified nodule in the right lower lung zone (arrow). Also seen are multiple calcified lymph nodes at the right hilum (arrowhead). (b, c) CT scans (mediastinal window, b; lung window, c) show a calcified nodule within a dilated bronchus (arrow). (d) Photograph of the resected specimen shows a yellowish brown calcified nodule within a bronchiectatic cavity (arrow). It proved to be a calcified lymph node at microscopic examination. Another small, calcified lymph node is adjacent to the broncholith (arrowhead). Although broncholithiasis is thought to be related to tuberculosis, no organism was identified with acid-fast staining.
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Figure 1b. Broncholithiasis due to extrusion of a calcified lymph node in a 41-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows an irregular calcified nodule in the right lower lung zone (arrow). Also seen are multiple calcified lymph nodes at the right hilum (arrowhead). (b, c) CT scans (mediastinal window, b; lung window, c) show a calcified nodule within a dilated bronchus (arrow). (d) Photograph of the resected specimen shows a yellowish brown calcified nodule within a bronchiectatic cavity (arrow). It proved to be a calcified lymph node at microscopic examination. Another small, calcified lymph node is adjacent to the broncholith (arrowhead). Although broncholithiasis is thought to be related to tuberculosis, no organism was identified with acid-fast staining.
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Figure 1c. Broncholithiasis due to extrusion of a calcified lymph node in a 41-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows an irregular calcified nodule in the right lower lung zone (arrow). Also seen are multiple calcified lymph nodes at the right hilum (arrowhead). (b, c) CT scans (mediastinal window, b; lung window, c) show a calcified nodule within a dilated bronchus (arrow). (d) Photograph of the resected specimen shows a yellowish brown calcified nodule within a bronchiectatic cavity (arrow). It proved to be a calcified lymph node at microscopic examination. Another small, calcified lymph node is adjacent to the broncholith (arrowhead). Although broncholithiasis is thought to be related to tuberculosis, no organism was identified with acid-fast staining.
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Figure 1d. Broncholithiasis due to extrusion of a calcified lymph node in a 41-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows an irregular calcified nodule in the right lower lung zone (arrow). Also seen are multiple calcified lymph nodes at the right hilum (arrowhead). (b, c) CT scans (mediastinal window, b; lung window, c) show a calcified nodule within a dilated bronchus (arrow). (d) Photograph of the resected specimen shows a yellowish brown calcified nodule within a bronchiectatic cavity (arrow). It proved to be a calcified lymph node at microscopic examination. Another small, calcified lymph node is adjacent to the broncholith (arrowhead). Although broncholithiasis is thought to be related to tuberculosis, no organism was identified with acid-fast staining.
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The most common symptoms of broncholithiasis are nonproductive cough frequently associated with hemoptysis and, less common, the presence of secondary infection after obstruction of the distal portion of the lung that causes pain, chills, and fever (1,4). In some cases, a history of expectoration of calcified material (lithoptysis) may prompt the diagnosis.
Even though broncholithiasis is endobronchial disease, bronchoscopy often fails to aid in a correct diagnosis, because the calcified endobronchial material is often obscured by overlying bronchial wall inflammation or is distal to inflamed and narrowed airways rendered inaccessible to bronchoscopy (2–5).
Most symptomatic broncholiths should be removed at thoracotomy. Lobectomy or segmentectomy is usually required, since removal of the calcified mass will almost certainly take a portion of the bronchial wall (6). If a broncholith is completely free within the bronchus, it can be removed bronchoscopically. However, an effort to remove a broncholith that is not completely detached from the bronchial wall may be accompanied by catastrophic hemorrhage due to the close proximity of the pulmonary artery branches to the bronchus. Preoperative diagnosis of broncholithiasis is important, because in most cases, the symptoms usually suggest a tumor.
In this study, we present the radiographic and computed tomographic (CT) features of broncholithiasis of variable pathogenesis with bronchoscopic and pathologic correlation. We also present several disease entities that mimic broncholithiasis, such as endobronchial calcified tumors and tracheobronchial disease with mural calcification, along with the pathologic correlation.
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Radiologic Findings and Technical Considerations
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Radiographic findings of broncholithiasis include the presence of a calcified nodule and airway obstruction such as atelectasis, mucoid impaction, bronchiectasis, or expiratory air trapping (2,4) (Figs 1, 2). Other radiographic findings include the disappearance of a previously identified calcified nidus or change in position of a calcified nidus on serial radiographs. Chest radiography often fails to show the calcification within the bronchus.
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Figure 2a. Broncholithiasis due to calcification of an aspirated foreign body in a 53-year-old man who presented with cough. (a, b) Posteroanterior (a) and lateral (b) radiographs show combined atelectasis of the right middle and lower lobes. A calcified irregular nodule is in the infrahilar area on the lateral chest radiograph (arrow, b). (c) CT scan shows a calcified nodule in the bronchus intermedius with atelectasis of the right lower lobe (arrow). (d) Bronchoscopic image shows a brownish, hard material in the bronchus intermedius. When removed bronchoscopically, it was found to be vegetable fiber with dystrophic calcification.
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Figure 2b. Broncholithiasis due to calcification of an aspirated foreign body in a 53-year-old man who presented with cough. (a, b) Posteroanterior (a) and lateral (b) radiographs show combined atelectasis of the right middle and lower lobes. A calcified irregular nodule is in the infrahilar area on the lateral chest radiograph (arrow, b). (c) CT scan shows a calcified nodule in the bronchus intermedius with atelectasis of the right lower lobe (arrow). (d) Bronchoscopic image shows a brownish, hard material in the bronchus intermedius. When removed bronchoscopically, it was found to be vegetable fiber with dystrophic calcification.
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Figure 2c. Broncholithiasis due to calcification of an aspirated foreign body in a 53-year-old man who presented with cough. (a, b) Posteroanterior (a) and lateral (b) radiographs show combined atelectasis of the right middle and lower lobes. A calcified irregular nodule is in the infrahilar area on the lateral chest radiograph (arrow, b). (c) CT scan shows a calcified nodule in the bronchus intermedius with atelectasis of the right lower lobe (arrow). (d) Bronchoscopic image shows a brownish, hard material in the bronchus intermedius. When removed bronchoscopically, it was found to be vegetable fiber with dystrophic calcification.
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Figure 2d. Broncholithiasis due to calcification of an aspirated foreign body in a 53-year-old man who presented with cough. (a, b) Posteroanterior (a) and lateral (b) radiographs show combined atelectasis of the right middle and lower lobes. A calcified irregular nodule is in the infrahilar area on the lateral chest radiograph (arrow, b). (c) CT scan shows a calcified nodule in the bronchus intermedius with atelectasis of the right lower lobe (arrow). (d) Bronchoscopic image shows a brownish, hard material in the bronchus intermedius. When removed bronchoscopically, it was found to be vegetable fiber with dystrophic calcification.
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CT, with its high spatial resolution and superior ability to depict calcification, usually provides useful information in the evaluation of suspected broncholithiasis (3,7,8) (Figs 1, 2). CT findings can be strongly suggestive of broncholithiasis when there is a calcified nodule that is either endobronchial or peribronchial and is associated with findings of bronchial obstruction, such as atelectasis, obstructive pneumonitis, or bronchiectasis. However, with conventional CT, it can be difficult to determine whether a calcified nodule is endobronchial in position because thicker sections result in a volume-averaging artifact of broncholith, bronchus, and peribronchial tissues, including adjacent lymph nodes (3) (Fig 3). In one study, only six of 10 calcified endobronchial lymph nodes were correctly interpreted with the use of conventional CT scans of 5–10-mm section thickness (3).
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Figure 3. Calcified peribronchial lymph node without intraluminal protrusion that mimicked a broncholith in a 67-year-old woman who presented with fever and blood-tinged sputum. CT scan obtained at the level of the left atrium shows atelectasis of the right middle lobe. Calcified lymph nodes adjacent to the bronchus (arrow) are suggestive of broncholithiasis. At bronchoscopy, the right middle lobar bronchus was narrow and inflamed, without evidence of an intraluminal location of the lymph node. Some authors may regard this case as a broncholithiasis when they use the broader definition of the term, even though the calcified material is not within the bronchus.
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To avoid partial volume averaging artifact and section misregistration artifact, volumetric data acquisition from helical CT performed with thin collimation is required (Figs 4, 5). Multiplanar reformation of helical CT data is usually helpful in showing whether the calcified material is endobronchial or peribronchial (9,10). CT scans viewed at the bone or wide window setting, that is, at the level of -300 HU and with a window of 1,800–2,000, are usually valuable to confirm calcification or ossification and to assess the morphology of a broncholith (Figs 4, 5).
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Figure 4. Utility of volumetric data acquisition with helical CT in the diagnosis of broncholithiasis in a 69-year-old woman who presented with hemoptysis. Serial CT scans obtained with a single breath hold, 3-mm collimation, pitch of 1, and a 3-mm reconstruction interval help confirm the endobronchial location of a calcified nodule in the basal bronchus of the right lower lobe (arrows). Enlargement of the left atrium is due to mitral stenosis. Bronchoscopy revealed a calcified nodule within the basal bronchus of the right lower lobe. Because the nodule was fixed to the bronchial wall, bronchoscopic removal was not performed.
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Figure 5a. Utility of thin-section helical CT and multiplanar reformation in the detection of a small broncholith in a 45-year-old woman who presented with cough. (a) CT scan obtained with 8-mm collimation shows a tubular calcified lesion in the right lower lobe (arrow). An area of peripheral air trapping (arrowheads) and suspicious bronchial structure seen at the medial portion of the nodule suggest an endobronchial location of the lesion. (b) CT scan obtained with 2.5-mm collimation and a wide window setting clearly shows the proximal part of the bronchus (arrow) and an impacted endobronchial calcified lesion. (c) Multiplanar reformatted image obtained with volumetric CT data also clearly shows the broncholith (arrow).
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Figure 5b. Utility of thin-section helical CT and multiplanar reformation in the detection of a small broncholith in a 45-year-old woman who presented with cough. (a) CT scan obtained with 8-mm collimation shows a tubular calcified lesion in the right lower lobe (arrow). An area of peripheral air trapping (arrowheads) and suspicious bronchial structure seen at the medial portion of the nodule suggest an endobronchial location of the lesion. (b) CT scan obtained with 2.5-mm collimation and a wide window setting clearly shows the proximal part of the bronchus (arrow) and an impacted endobronchial calcified lesion. (c) Multiplanar reformatted image obtained with volumetric CT data also clearly shows the broncholith (arrow).
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Figure 5c. Utility of thin-section helical CT and multiplanar reformation in the detection of a small broncholith in a 45-year-old woman who presented with cough. (a) CT scan obtained with 8-mm collimation shows a tubular calcified lesion in the right lower lobe (arrow). An area of peripheral air trapping (arrowheads) and suspicious bronchial structure seen at the medial portion of the nodule suggest an endobronchial location of the lesion. (b) CT scan obtained with 2.5-mm collimation and a wide window setting clearly shows the proximal part of the bronchus (arrow) and an impacted endobronchial calcified lesion. (c) Multiplanar reformatted image obtained with volumetric CT data also clearly shows the broncholith (arrow).
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Causes of Broncholithiasis
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Erosion by and Extrusion of Calcified Peribronchial Lymph Nodes
This phenomenon is by far the most common pathogenetic mechanism of broncholithiasis. It is usually associated with long-standing foci of necrotizing granulomatous lymphadenitis; any organism leading to such inflammation, including Mycobacterium tuberculosis (Figs 1, 6, 7), Histoplasma capsulatum, Coccidioides immitis, and a variety of others, can theoretically cause this complication (1,11). Even though it is the most common pathogenic mechanism, the frequency of broncholithiasis complicating granulomatous infection is quite low (12). A few cases with silicosis have been reported (13). Broncholiths are variable in size and usually irregular in shape and often possess spurlike projections or sharp edges (Fig 1). It is thought that repeated physical impingement of calcified peribronchial lymph nodes on the bronchial wall during respiratory motion is responsible for the broncholith formation (1,4). Preferential sites are known to be the proximal right middle lobe bronchus and the origin of the anterior segmental bronchus of the upper lobes because of airway anatomy and lymph node distribution (4,6). Rare complications include bronchoesophageal or bronchoaortic fistula formation. Histologic examination of broncholiths typically shows amorphous or sometimes laminated necrotic material with extensive dystrophic calcification. Organisms within the material may be identified with appropriate special stains. The adjacent bronchial wall is invariably inflamed and may be ulcerated.
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Figure 6a. Broncholithiasis due to extrusion of a calcified lymph node in a 50-year-old man who presented with cough and who had undergone treatment with antituberculous drugs owing to microscopically proved pulmonary tuberculosis 10 years previously. (a) Posteroanterior radiograph shows consolidation in the left perihilar area. A small, radiopaque nodule is seen in the central portion of the lesion (arrowhead). (b) CT scan shows a small, irregular calcified nodule in the superior segmental bronchus of the left lower lobe (arrow) with peripheral consolidation and nodular opacity. Also seen are calcified lymph nodes at the subcarinal nodal station and adjacent to segmental bronchi of the right middle lobe and right lower lobe (arrowheads). Bronchoscopy revealed a broncholith, which was removed.
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Figure 6b. Broncholithiasis due to extrusion of a calcified lymph node in a 50-year-old man who presented with cough and who had undergone treatment with antituberculous drugs owing to microscopically proved pulmonary tuberculosis 10 years previously. (a) Posteroanterior radiograph shows consolidation in the left perihilar area. A small, radiopaque nodule is seen in the central portion of the lesion (arrowhead). (b) CT scan shows a small, irregular calcified nodule in the superior segmental bronchus of the left lower lobe (arrow) with peripheral consolidation and nodular opacity. Also seen are calcified lymph nodes at the subcarinal nodal station and adjacent to segmental bronchi of the right middle lobe and right lower lobe (arrowheads). Bronchoscopy revealed a broncholith, which was removed.
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Figure 7a. Broncholithiasis due to extrusion of a calcified lymph node in a 61-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows consolidation in the right lower lobe. Calcified granulomas in the right apex (boxed area) and calcified right paratracheal lymph nodes due to previous tuberculosis (arrowheads) are also shown. (b) CT scan shows a calcified nodule (arrowhead) in the anterior basal segmental bronchus of the right lower lobe with atelectasis. (c) Bronchoscopic image shows a yellowish hard material with surrounding granulation tissue (arrow), which was removed.
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Figure 7b. Broncholithiasis due to extrusion of a calcified lymph node in a 61-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows consolidation in the right lower lobe. Calcified granulomas in the right apex (boxed area) and calcified right paratracheal lymph nodes due to previous tuberculosis (arrowheads) are also shown. (b) CT scan shows a calcified nodule (arrowhead) in the anterior basal segmental bronchus of the right lower lobe with atelectasis. (c) Bronchoscopic image shows a yellowish hard material with surrounding granulation tissue (arrow), which was removed.
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Figure 7c. Broncholithiasis due to extrusion of a calcified lymph node in a 61-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows consolidation in the right lower lobe. Calcified granulomas in the right apex (boxed area) and calcified right paratracheal lymph nodes due to previous tuberculosis (arrowheads) are also shown. (b) CT scan shows a calcified nodule (arrowhead) in the anterior basal segmental bronchus of the right lower lobe with atelectasis. (c) Bronchoscopic image shows a yellowish hard material with surrounding granulation tissue (arrow), which was removed.
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Aspiration of Radiopaque Fragments or in Situ Calcification of Foreign Material
It is well known that foreign body aspiration is more common in children than in adults, its peak incidence occurring during the second year of life among children and during the sixth decade among adults (14,15). The many factors that predispose adults to foreign body aspiration include neurologic dysfunction, trauma with loss of consciousness, facial trauma, intubation, dental procedures, and sedative uses. In rare cases, bone fragments or other radiopaque material may be aspirated (16) (Fig 8). Radiologic findings include radiopaque nodules within the tracheobronchial tree with or without postobstructive changes. When a noncalcified foreign body, such as vegetable fiber, remains within the bronchus for a prolonged period, calcium may deposit around the nucleus of the foreign body (Fig 2).
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Figure 8a. Broncholithiasis due to aspirated calcified material in a 48-year-old woman who presented with cough. (a) CT scan shows a tubular calcified lesion at the orifice of the left upper lobar bronchus (arrow). (b) Three-dimensional image obtained with a volume-rendering technique clearly shows the lesion with yellow color (arrow) within the bronchus. (c) Photograph obtained after bronchoscopic removal shows the lesion was an anchovy.
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Figure 8b. Broncholithiasis due to aspirated calcified material in a 48-year-old woman who presented with cough. (a) CT scan shows a tubular calcified lesion at the orifice of the left upper lobar bronchus (arrow). (b) Three-dimensional image obtained with a volume-rendering technique clearly shows the lesion with yellow color (arrow) within the bronchus. (c) Photograph obtained after bronchoscopic removal shows the lesion was an anchovy.
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Figure 8c. Broncholithiasis due to aspirated calcified material in a 48-year-old woman who presented with cough. (a) CT scan shows a tubular calcified lesion at the orifice of the left upper lobar bronchus (arrow). (b) Three-dimensional image obtained with a volume-rendering technique clearly shows the lesion with yellow color (arrow) within the bronchus. (c) Photograph obtained after bronchoscopic removal shows the lesion was an anchovy.
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Erosion by and Extrusion of Calcified Bronchial Cartilage Plates
Diffuse tracheobronchial calcification is commonly associated with advanced age (17). CT revealed calcification of tracheobronchial cartilage in 26% of patients aged 40–59 years and in up to 65% of men and 40.5% of women aged 60–79 years (18). In rare cases, broncholithiasis occurs as a result of calcification of bronchial cartilage with subsequent sequestration of the calcified material into the bronchial lumen (1).
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Diseases That Mimic Broncholithiasis
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Primary Endobronchial Infection
A fungus ball can be defined as a conglomeration of intervened fungal hyphae admixed with mucus and cellular debris within the pulmonary cavity or ectatic bronchus (19). Calcification of the fungus ball occurs in some cases; it may appear as scattered small nodules, as a fine rim around the periphery of the mass, or as an extensive process that involves the greater part of the mycetoma (Fig 9). In rare cases, primary endobronchial actinomycosis may calcify and result in the formation of a calcified endobronchial nodule (20,21) (Fig 10). In some reports, endobronchial actinomycosis has been associated with preexisting broncholithiasis (22,23).
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Figure 9a. Calcified aspergilloma within a dilated bronchus mimicking broncholithiasis in a 31-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows a round mass with nodular calcification in the left lower zone (arrow). (b) CT scan shows the mass within an ectatic bronchus with an air crescent sign (arrow). At pathologic examination, the entire mycelial mass was within the bronchus and without evidence of parenchymal invasion. The high-attenuation area seen at CT was dystrophic calcification of the fungus ball.
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Figure 9b. Calcified aspergilloma within a dilated bronchus mimicking broncholithiasis in a 31-year-old woman who presented with hemoptysis. (a) Posteroanterior radiograph shows a round mass with nodular calcification in the left lower zone (arrow). (b) CT scan shows the mass within an ectatic bronchus with an air crescent sign (arrow). At pathologic examination, the entire mycelial mass was within the bronchus and without evidence of parenchymal invasion. The high-attenuation area seen at CT was dystrophic calcification of the fungus ball.
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Figure 10a. Primary endobronchial actinomycosis with dystrophic calcification mimicking broncholithiasis in a 61-year-old man who presented with left-sided chest pain. (a) CT scan shows a calcified nodule within the bronchus of the lingular division of the left upper lobe (arrow) with peripheral atelectasis. At bronchoscopy, a yellowish, hard material was seen to obstruct the bronchial lumen. Because the lesion was firmly attached to the bronchial wall, removal of it with a bronchoscopic forceps was impossible. (b) Photomicrograph (original magnification, x10; H-E stain) of a section obtained along the axis of the bronchus shows that the mass was partly calcified ( ) and within the bronchus but did not infiltrate into the pulmonary parenchyma. There was no evidence of a coexisting foreign material or a calcified lymph node. (c) Photomicrograph (original magnification, x400; H-E stain) shows sulfur granules surrounded by eosinophilic "clubbing" materials (arrows); this finding is typical for actinomycosis. (Reprinted, with permission, from reference 21.)
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Figure 10b. Primary endobronchial actinomycosis with dystrophic calcification mimicking broncholithiasis in a 61-year-old man who presented with left-sided chest pain. (a) CT scan shows a calcified nodule within the bronchus of the lingular division of the left upper lobe (arrow) with peripheral atelectasis. At bronchoscopy, a yellowish, hard material was seen to obstruct the bronchial lumen. Because the lesion was firmly attached to the bronchial wall, removal of it with a bronchoscopic forceps was impossible. (b) Photomicrograph (original magnification, x10; H-E stain) of a section obtained along the axis of the bronchus shows that the mass was partly calcified () and within the bronchus but did not infiltrate into the pulmonary parenchyma. There was no evidence of a coexisting foreign material or a calcified lymph node. (c) Photomicrograph (original magnification, x400; H-E stain) shows sulfur granules surrounded by eosinophilic "clubbing" materials (arrows); this finding is typical for actinomycosis. (Reprinted, with permission, from reference 21.)
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Figure 10c. Primary endobronchial actinomycosis with dystrophic calcification mimicking broncholithiasis in a 61-year-old man who presented with left-sided chest pain. (a) CT scan shows a calcified nodule within the bronchus of the lingular division of the left upper lobe (arrow) with peripheral atelectasis. At bronchoscopy, a yellowish, hard material was seen to obstruct the bronchial lumen. Because the lesion was firmly attached to the bronchial wall, removal of it with a bronchoscopic forceps was impossible. (b) Photomicrograph (original magnification, x10; H-E stain) of a section obtained along the axis of the bronchus shows that the mass was partly calcified () and within the bronchus but did not infiltrate into the pulmonary parenchyma. There was no evidence of a coexisting foreign material or a calcified lymph node. (c) Photomicrograph (original magnification, x400; H-E stain) shows sulfur granules surrounded by eosinophilic "clubbing" materials (arrows); this finding is typical for actinomycosis. (Reprinted, with permission, from reference 21.)
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Calcified Endobronchial Tumor
Carcinoid tumors do not commonly appear to be calcified at CT. In one CT study, 26% of the patients had intratumoral calcification of the carcinoid tumor (24). Calcification or ossification is more common in central carcinoid tumors (39%) than in the peripheral type (8%). When carcinoid tumor is totally ossified and within the bronchus, it simulates broncholithiasis (25) (Fig 11).
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Figure 11a. Atypical carcinoid with ossification mimicking broncholithiasis in a 41-year-old man who presented with dyspnea. (a) Magnified view of a posteroanterior radiograph shows a nodular opacity at the right hilum (arrow). (b) CT scan shows a sharply defined, totally ossified mass (arrow) centrally situated in the right lower lobar bronchus; the mass produces abrupt bronchial obstruction. Analysis of the resected specimen revealed atypical carcinoid, the majority of which was ossified.
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Figure 11b. Atypical carcinoid with ossification mimicking broncholithiasis in a 41-year-old man who presented with dyspnea. (a) Magnified view of a posteroanterior radiograph shows a nodular opacity at the right hilum (arrow). (b) CT scan shows a sharply defined, totally ossified mass (arrow) centrally situated in the right lower lobar bronchus; the mass produces abrupt bronchial obstruction. Analysis of the resected specimen revealed atypical carcinoid, the majority of which was ossified.
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Hamartoma is one of the most common benign lung tumors. Most hamartomas are in the lung parenchyma, and only rarely do they occur within the bronchi (26). At histopathologic examination, endobronchial hamartomas tend to have fewer epithelial clefts, a decreased proportion of cartilage, and a correspondingly increased adipose tissue component. When a central cartilaginous core exists, it can mimic a broncholith (27) (Fig 12). Other less common calcified or ossified endobronchial tumors include amyloidomas, osteomas, osteosarcomas, chondromas, and chondrosarcomas.
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Figure 12a. Calcified endobronchial hamartoma mimicking broncholithiasis in a 48-year-old man who presented with cough. Chest radiography (not shown) revealed atelectasis of the right upper lobe. (a) CT scan shows a small, calcified nodule obstructing the right upper lobar bronchus (arrow). (b) Bronchoscopic image shows a yellowish movable mass at the orifice of the right upper lobar bronchus (arrow). Bronchoscopic biopsy revealed chronic inflammation. (c) Photograph of the resected specimen shows a round, reddish endobronchial mass (arrow). The cut surface of the mass was white and firm (not shown). (d) Photomicrograph (original magnification, x100; H-E stain) shows the mass is covered with normal respiratory epithelium. Areas of bone and cartilage tissue () and mature fat tissue are mixed.
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Figure 12b. Calcified endobronchial hamartoma mimicking broncholithiasis in a 48-year-old man who presented with cough. Chest radiography (not shown) revealed atelectasis of the right upper lobe. (a) CT scan shows a small, calcified nodule obstructing the right upper lobar bronchus (arrow). (b) Bronchoscopic image shows a yellowish movable mass at the orifice of the right upper lobar bronchus (arrow). Bronchoscopic biopsy revealed chronic inflammation. (c) Photograph of the resected specimen shows a round, reddish endobronchial mass (arrow). The cut surface of the mass was white and firm (not shown). (d) Photomicrograph (original magnification, x100; H-E stain) shows the mass is covered with normal respiratory epithelium. Areas of bone and cartilage tissue () and mature fat tissue are mixed.
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Figure 12c. Calcified endobronchial hamartoma mimicking broncholithiasis in a 48-year-old man who presented with cough. Chest radiography (not shown) revealed atelectasis of the right upper lobe. (a) CT scan shows a small, calcified nodule obstructing the right upper lobar bronchus (arrow). (b) Bronchoscopic image shows a yellowish movable mass at the orifice of the right upper lobar bronchus (arrow). Bronchoscopic biopsy revealed chronic inflammation. (c) Photograph of the resected specimen shows a round, reddish endobronchial mass (arrow). The cut surface of the mass was white and firm (not shown). (d) Photomicrograph (original magnification, x100; H-E stain) shows the mass is covered with normal respiratory epithelium. Areas of bone and cartilage tissue () and mature fat tissue are mixed.
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Figure 12d. Calcified endobronchial hamartoma mimicking broncholithiasis in a 48-year-old man who presented with cough. Chest radiography (not shown) revealed atelectasis of the right upper lobe. (a) CT scan shows a small, calcified nodule obstructing the right upper lobar bronchus (arrow). (b) Bronchoscopic image shows a yellowish movable mass at the orifice of the right upper lobar bronchus (arrow). Bronchoscopic biopsy revealed chronic inflammation. (c) Photograph of the resected specimen shows a round, reddish endobronchial mass (arrow). The cut surface of the mass was white and firm (not shown). (d) Photomicrograph (original magnification, x100; H-E stain) shows the mass is covered with normal respiratory epithelium. Areas of bone and cartilage tissue () and mature fat tissue are mixed.
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Tracheobronchial Diseases with Mural Calcification
Tracheobronchial amyloidosis is the most common form of respiratory system involvement and usually involves the distal part of the trachea and bronchi (28). It represents abnormal deposition of amyloid, an autologous fibrillar protein material that histochemically binds with Congo red stain and shows green birefringence in polarized light. It shows localized or diffuse involvement of the tracheobronchial tree with submucosal deposition of amyloid plaques or nodules. Radiographs and CT scans show focal or diffuse narrowing of the airway by nodular submucosal deposits that protrude into the lumen. It may form a polypoid nodule with stippled calcification, thus mimicking a broncholith (28,29) (Fig 13).
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Figure 13a. Bronchial amyloidosis with mural calcification mimicking broncholithiasis in a 53-year-old woman. (a, b) CT scans show localized thickening of the bronchial wall with calcification and partial intraluminal protrusion (arrow, a; arrows, b). (c) Photomicrograph (original magnification, x65; H-E stain) of the transbronchial lung biopsy specimen shows eosinophilic material (arrow) in the perivascular space. (d) Photomicrograph (original magnification, x65; Congo red stain under polarized light) shows apple green birefringent material (arrows). (Fig 13 b-d reprinted, with permission, from reference 28.)
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Figure 13b. Bronchial amyloidosis with mural calcification mimicking broncholithiasis in a 53-year-old woman. (a, b) CT scans show localized thickening of the bronchial wall with calcification and partial intraluminal protrusion (arrow, a; arrows, b). (c) Photomicrograph (original magnification, x65; H-E stain) of the transbronchial lung biopsy specimen shows eosinophilic material (arrow) in the perivascular space. (d) Photomicrograph (original magnification, x65; Congo red stain under polarized light) shows apple green birefringent material (arrows). (Fig 13 b-d reprinted, with permission, from reference 28.)
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Figure 13c. Bronchial amyloidosis with mural calcification mimicking broncholithiasis in a 53-year-old woman. (a, b) CT scans show localized thickening of the bronchial wall with calcification and partial intraluminal protrusion (arrow, a; arrows, b). (c) Photomicrograph (original magnification, x65; H-E stain) of the transbronchial lung biopsy specimen shows eosinophilic material (arrow) in the perivascular space. (d) Photomicrograph (original magnification, x65; Congo red stain under polarized light) shows apple green birefringent material (arrows). (Fig 13 b-d reprinted, with permission, from reference 28.)
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Figure 13d. Bronchial amyloidosis with mural calcification mimicking broncholithiasis in a 53-year-old woman. (a, b) CT scans show localized thickening of the bronchial wall with calcification and partial intraluminal protrusion (arrow, a; arrows, b). (c) Photomicrograph (original magnification, x65; H-E stain) of the transbronchial lung biopsy specimen shows eosinophilic material (arrow) in the perivascular space. (d) Photomicrograph (original magnification, x65; Congo red stain under polarized light) shows apple green birefringent material (arrows). (Fig 13 b-d reprinted, with permission, from reference 28.)
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Tracheobronchopathia osteochondroplastica is an idiopathic condition characterized by submucosal osteocartilaginous growth along the anterolateral wall of the trachea and main bronchi (30). Protrusion of the submucosal nodules into the lumen causes distortion and narrowing of the airway. When the disease extends into a bronchus as it usually does, it can cause lobar collapse.
Hypertrophied Bronchial Artery with Intraluminal Protrusion
The bronchial arteries become enlarged in various diseases, including acute or chronic pulmonary infections, pulmonary thromboembolism, and chronic obstructive pulmonary disease (31). A hypertrophied bronchial artery may protrude into the bronchial lumen, thus mimicking a broncholith at contrast-enhanced CT (Fig 14). In one series, intraluminal protrusion of an enlarged bronchial artery was seen in eight of 14 patients (31). Careful scrutiny of the images obtained above and below the abnormality or unenhanced CT is sometimes needed to confirm the vascular nature of the lesion.
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Figure 14a. Hypertrophied bronchial artery at enhanced CT mimicking broncholithiasis in a 41-year-old woman. (a) Contrast-enhanced CT scan shows a high-attenuation nodular structure (arrow) at the bifurcation of the bronchus intermedius, which mimics broncholithiasis. (b) Thin-section CT scan reveals that the high-attenuation structure in a is not calcified. (Reprinted, with permission, from reference 31.)
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Figure 14b. Hypertrophied bronchial artery at enhanced CT mimicking broncholithiasis in a 41-year-old woman. (a) Contrast-enhanced CT scan shows a high-attenuation nodular structure (arrow) at the bifurcation of the bronchus intermedius, which mimics broncholithiasis. (b) Thin-section CT scan reveals that the high-attenuation structure in a is not calcified. (Reprinted, with permission, from reference 31.)
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Differential Diagnosis
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The differential diagnosis of high-attenuation endobronchial lesions can be narrowed by carefully obtaining the patient history and evaluating CT findings. In cases of broncholithiasis due to erosion by calcified peribronchial lymph nodes, the most common cause, CT usually shows lymph nodes with or without calcification at other locations and parenchymal changes due to infection by causative organisms, in addition to the typical findings of broncholithiasis (Figs 1, 6, 7). Sometimes peribronchial lymph nodes, which do not erode into the bronchial lumen, may mimic broncholiths (Fig 3). In such cases, helical CT with thin collimation is required to confirm the exact location of the node (Figs 4, 5). In cases of an aspirated foreign body, the airways and pulmonary parenchyma are usually normal except for the broncholith (Figs 2, 8). Calcification of other parts of the tracheobronchial wall is usually seen in cases of broncholithiasis due to erosion and extrusion of calcified bronchial cartilage plates and tracheobronchopathia osteochondroplastica. Noncalcified thickening of the airway wall helps in the diagnosis of tracheobronchial amyloidosis (Fig 13). The detection of fat content within an endobronchial lesion is important in diagnosing endobronchial hamartoma. Careful examination of contiguous images, or images obtained at non-contrast-enhanced CT, may be necessary to differentiate a hypertrophied bronchial artery protruding into the bronchial lumen from a broncholith (Fig 14).
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Conclusions
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Even though the most common cause of broncholithiasis is erosion of the bronchial wall and intraluminal protrusion of a calcified peribronchial lymph node caused by granulomatous infection such as tuberculosis and histoplasmosis, there are several other pathogeneses. In addition, endobronchial tumors with calcification or tracheobronchial disease with mural calcification can mimic broncholithiasis. Awareness of the various causes of broncholithiasis and its mimics, as well as awareness of the typical radiologic features, is helpful in obtaining an accurate diagnosis and providing adequate patient management.
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References
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- Fraser RS, Müller NL, Colman N, Paré PD. Fraser and Paré’s diagnosis of diseases of the chest 4th ed. Philadelphia, Pa: Saunders, 1999; 2287-2289.
- Vix VA. Radiolographic manifestations of broncholithiasis. Radiology 1978; 128:295-299.[Abstract]
- Conces DJ, Jr, Tarver RD, Vix VA. Broncholithiasis: CT features in 15 patients. AJR Am J Roentgenol 1991; 157:249-253.[Abstract/Free Full Text]
- Kelley WA. Broncholithiasis: current concepts of an ancient disease. Postgrad Med 1979; 66:81-86, 88, 90.
- Dixon GF, Donnerberg RL, Schonfeld SA, Whitcomb ME. Advances in the diagnosis and treatment of broncholithiasis. Am Rev Respir Dis 1984; 129:1028-1030.[Medline]
- Faber LP, Jensik RJ, Chawla SK, Kittle CF. The surgical implication of broncholithiasis. J Thorac Cardiovasc Surg 1975; 70:779-789.[Abstract]
- Kowai LE, Goodman LR, Zarro VJ, Haskin M. CT diagnosis of broncholithiasis. J Comput Assist Tomogr 1983; 7:321-323.
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