(Radiographics. 2001;21:387-402.)
© RSNA, 2001
Systemic Arterial Supply to the Lungs in Adults: Spiral CT Findings1
Kyung-Hyun Do, MD,
Jin Mo Goo, MD,
Jung-Gi Im, MD,
Kyoung Won Kim, MD,
Jin Wook Chung, MD and
Jae Hyung Park, MD
1 From the Departments of Radiology, Seoul National University Hospital and Seoul National University College of Medicine and Clinical Research Institute, 28 Yongon-dong, Chongno-gu, Seoul 110-744, South Korea. Presented as a scientific exhibit at the 1999 RSNA scientific assembly. Received April 3, 2000; revision requested May 17 and received July 12; accepted July 13. Supported in part by a grant from Brain Korea 21. Address correspondence to J.G.I. (e-mail: imjg@radcom.snu.ac.kr).
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Abstract
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Systemic arterial supply to the lungs can be congenital or due to acquired disease. Congenital diseases encompass bronchopulmonary sequestration and congenital pulmonary venolobar syndrome, in which the involved lung parenchyma is supplied by the aberrant systemic arteries. An anomalous systemic artery can also supply an area of otherwise normal lung parenchyma. In acquired diseases, hypertrophied normal systemic arteries supply the lungs. Hypertrophied systemic arteries include the bronchial arteries, intercostal arteries, internal mammary arteries, inferior phrenic arteries, branches of the thyrocervical trunk, branches of the hepatic arteries, and branches of the abdominal aorta. Hypertrophy of normal systemic arteries is encountered in patients with bronchiectasis, pulmonary tuberculosis, other pulmonary infections, pulmonary thromboembolism, or chronic obstructive pulmonary disease. These systemic arteries are considered to supply the lungs by means of anastomoses between bronchial and pulmonary arteries within the lung parenchyma or transpleural systemic-pulmonary artery anastomoses. In most cases, the correct diagnosis and treatment plan can be determined by identification of the systemic arteries on computed tomographic scans.
Index Terms: Arteries, bronchial, 563.1556, 60.1422, 943.15 • Bronchopulmonary sequestration, 60.1422, 60.1451, 943.15 • Computed tomography (CT), helical, 60.12115 • Lung, abnormalities, 60.14 • Pneumonitis, 60.2 • Pulmonary arteries, abnormalities, 564.1556, 60.1422 • Pulmonary arteries, stenosis or obstruction, 564.625 • Venolobar syndrome, 60.142
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LEARNING OBJECTIVES FOR TEST 3
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After reading this article and taking the test, the reader will be able to:
- Recognize systemic arteries supplying the lungs in a variety of diseases on spiral CT scans.
- List the spectrum of diseases that cause systemic arterial supply to the lungs.
- Describe how to differentiate systemic arterial supply to the lungs from other causes of dilatation of mediastinal vessels.
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Introduction
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Systemic arterial supply to the lungs has been described in many cases of congenital heart and lung diseases, which are usually diagnosed during infancy or early childhood. However, in some patients, congenital diseases are diagnosed during adulthood because their symptoms are absent or manifest late. Systemic arterial supply to the lungs can also occur in acquired lung diseases, such as bronchiectasis and inflammatory lung disease. In some cases, identification of the systemic arterial supply to the lungs may be critical in establishment of the correct radiologic diagnosis. Therefore, angiography was not infrequently performed to demonstrate systemic arterial supply to the lungs. Recently, with the development of spiral computed tomography (CT), systemic arterial supply to the lungs is more frequently found at CT, avoiding the need for angiography. We have categorized systemic arterial supply to the lungs as follows: (a) hypertrophied normal systemic arteries related to bronchiectasis or other chronic inflammation and (b) aberrant systemic arteries in bronchopulmonary sequestration, congenital pulmonary venolobar syndrome, and normal lung parenchyma. Bronchial and pulmonary artery anastomoses within the lung parenchyma and transpleural systemic-pulmonary artery anastomoses are included in the former category.
In this article, we present the spiral CT findings of patients with systemic arterial supply to the lungs. Familiarity with these imaging features will help establish an accurate diagnosis of various acquired and congenital lung diseases.
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Hypertrophied Normal Systemic Arteries
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Chronic Inflammatory Diseases
Systemic arterialization of the lung is usually congenital (1). However, in patients with chronic pulmonary inflammation, large anastomoses can develop between systemic and pulmonary arteries. Most commonly, systemic-pulmonary artery anastomoses occur between the bronchial artery and peripheral branches of the pulmonary artery. In addition to anastomoses between bronchial and pulmonary arteries within the lung parenchyma, transpleural systemic-pulmonary artery anastomoses can develop in the presence of pleural adhesions (2)–(5). The inflammation incites neovascularization of the involved portion of the lung, which may resolve once the inflammation has abated. The anastomoses may reflect dilatation of normal precapillary or capillary anastomoses, anastomosis of vessels in granulation tissue arising from both arterial systems, or recanalization of thrombosed pulmonary artery branches by enlarged vasa vasorum (5).
The systemic arteries become enlarged in various diseases, including bronchiectasis, pulmonary tuberculosis, other pulmonary infections, and chronic obstructive pulmonary disease (2),(6)–(9).
Hypertrophied Bronchial Arteries and Bronchial-to-Pulmonary Artery Anastomoses.
The bronchial artery is the main source of blood supply for the bronchi. The bronchial arteries provide the normal systemic arterial supply to the lungs after birth and generally comprise one to three small arteries from the upper dorsal aorta or right intercostal artery supplying each lung (6),(10).
The normal bronchial artery is a small (<2 mm in diameter) vessel that arises directly from the descending thoracic aorta (11),(12). Enlarge-ment of the bronchial arteries is more prominent in bronchial disease (Fig 1) than in bronchiolar or parenchymal lung disease (2). In cases of bronchiectasis, blood circulation in the bronchi can increase and may represent as much as 30% of cardiac output. Enlargement of the bronchial vessels is associated with the development of granulation tissue during the course of the inflammatory changes in the wall. In patients with chronic pulmonary parenchymal inflammation, preexisting connections between the bronchial and pulmonary arteries become functional at the pre- and postcapillary levels, often creating a source of hemoptysis. In postprimary pulmonary tuberculosis, significant pulmonary bleeding occurs in 8% of patients and is fatal in 1%–5% (13). In these patients, the bleeding is most commonly from hypertrophied bronchial arteries due to bronchiectasis, ongoing chronic inflammation (Fig 2), or intracavitary mycetomas (13),(14). Bleeding occurs less commonly in patients with active cavitary disease and associated granulomatous vasculitis (14). Surgery or transcatheter embolization may be required to treat massive bleeding (13). Therefore, in a patient who has had an episode of hemoptysis, knowledge that a bronchial artery is enlarged is useful information for diagnosis and treatment planning (15).
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Figure 1a. Bronchiectasis with a hypertrophied bronchial artery in a 40-year-old man. (a) Posteroanterior chest radiograph shows crowding of the bronchovascular bundle and peribronchial infiltration in both lower lung zones. (b) Right posterior oblique shaded-surface display image from CT angiography shows a hypertrophied right bronchial artery originating directly from the thoracic aorta (arrow). (c) Coronal multiplanar reconstruction image shows the hypertrophied right bronchial artery in the right infrahilar area (arrows). A slightly enlarged left bronchial artery is also seen (arrowheads).
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Figure 1b. Bronchiectasis with a hypertrophied bronchial artery in a 40-year-old man. (a) Posteroanterior chest radiograph shows crowding of the bronchovascular bundle and peribronchial infiltration in both lower lung zones. (b) Right posterior oblique shaded-surface display image from CT angiography shows a hypertrophied right bronchial artery originating directly from the thoracic aorta (arrow). (c) Coronal multiplanar reconstruction image shows the hypertrophied right bronchial artery in the right infrahilar area (arrows). A slightly enlarged left bronchial artery is also seen (arrowheads).
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Figure 1c. Bronchiectasis with a hypertrophied bronchial artery in a 40-year-old man. (a) Posteroanterior chest radiograph shows crowding of the bronchovascular bundle and peribronchial infiltration in both lower lung zones. (b) Right posterior oblique shaded-surface display image from CT angiography shows a hypertrophied right bronchial artery originating directly from the thoracic aorta (arrow). (c) Coronal multiplanar reconstruction image shows the hypertrophied right bronchial artery in the right infrahilar area (arrows). A slightly enlarged left bronchial artery is also seen (arrowheads).
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Figure 2a. Pulmonary tuberculosis in a 52-year-old man. (a) Spiral CT scan of the chest shows a hypertrophied right bronchial artery originating from the thoracic aorta in the retrobronchial area (arrow). Chronic fibrotic changes in the apical regions of both upper lobes and bilateral pleural thickening are also seen. The high-attenuation lesion in the right upper lobe is a calcified granuloma; it also demonstrated high attenuation on a nonenhanced CT scan (not shown). (b) Selective bronchial angiogram shows the hypertrophied right bronchial artery supplying the right upper and middle lung zones.
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Figure 2b. Pulmonary tuberculosis in a 52-year-old man. (a) Spiral CT scan of the chest shows a hypertrophied right bronchial artery originating from the thoracic aorta in the retrobronchial area (arrow). Chronic fibrotic changes in the apical regions of both upper lobes and bilateral pleural thickening are also seen. The high-attenuation lesion in the right upper lobe is a calcified granuloma; it also demonstrated high attenuation on a nonenhanced CT scan (not shown). (b) Selective bronchial angiogram shows the hypertrophied right bronchial artery supplying the right upper and middle lung zones.
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By considering the normal anatomy and the course of the bronchial artery, we can anticipate the locations of hypertrophied bronchial arteries on CT scans. The right intercostobronchial artery commonly has an initial vertical or oblique course upward and to the right from the retroesophageal space within the mediastinum after arising from the aorta. The left bronchial artery usually originates from the anterior surface of the thoracic aorta or from the concavity of the aortic arch. At spiral CT enhanced with intravenously administered contrast material, bronchial arteries are demonstrated as nodular or linear structures within the mediastinal soft tissue and central airway that have the same attenuation as the thoracic aorta (Fig 3). The major locations of hypertrophied bronchial arteries are the retrotracheal area, retroesophageal area, posterior wall of the main bronchus, and aortopulmonary window (8),(12),(16). The azygos vein and retroaortic anastomoses of the azygos system can be mistaken for bronchial arteries if enhanced by reflux of contrast material from the superior vena cava (17). Successive caudal CT scans obtained during a different phase of peak enhancement will help differentiate these two entities. Mediastinal lymph nodes and the esophageal wall enhanced with contrast material should be carefully distinguished from the bronchial artery (12).
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Figure 3a. Bronchiectasis with hypertrophied bronchial arteries in the mediastinal soft tissue in a 75-year-old woman. (a) Spiral CT scan shows multiple nodular and curvilinear areas of increased attenuation (arrows) within the mediastinal soft tissue and at the posterior wall of the right main bronchus; these areas of increased attenuation have the same enhancement as the thoracic aorta and represent systemic arteries. (b) Spiral CT scan shows a collapsed left lower lobe (arrow) and multiple vascular structures (arrowheads) within the mediastinal soft tissue and in the central bronchovascular bundle, which are suggestive of branches of the bronchial artery.
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Figure 3b. Bronchiectasis with hypertrophied bronchial arteries in the mediastinal soft tissue in a 75-year-old woman. (a) Spiral CT scan shows multiple nodular and curvilinear areas of increased attenuation (arrows) within the mediastinal soft tissue and at the posterior wall of the right main bronchus; these areas of increased attenuation have the same enhancement as the thoracic aorta and represent systemic arteries. (b) Spiral CT scan shows a collapsed left lower lobe (arrow) and multiple vascular structures (arrowheads) within the mediastinal soft tissue and in the central bronchovascular bundle, which are suggestive of branches of the bronchial artery.
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Bronchial arteries exhibit considerable anatomic variation in terms of origin, course, and branching pattern. They usually arise directly from the proximal descending thoracic aorta or its branches; however, more than 20% of bronchial arteries have an anomalous origin from the aortic arch (11),(15). Therefore, demonstration of bronchial arteries with spiral CT is useful prior to interventional procedures involving the bronchial arteries. In addition, detection of lung parenchymal lesions is helpful for localizing the site of bleeding and selecting bronchial arteries for the interventional approach (16). If a hypertrophied bronchial artery is located in the peribronchial area, demonstration of the hypertrophied bronchial artery can be valuable for the bronchoscopist to avoid accidental biopsy of this artery (18).
Transpleural Systemic-Pulmonary Artery Anastomoses.
Transpleural systemic-pulmonary artery anastomoses develop in the presence of pleural adhesions. Pseudosequestration involves the combination of systemic arterial supply to the lungs with normal bronchial connections and coexistent infection (Fig 4). The systemic vessels can be the intercostal arteries, internal mammary arteries, inferior phrenic arteries, branches of the thyrocervical trunk, branches of the hepatic arteries, abdominal arteries, or other regional arteries.
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Figure 4a. Pseudosequestration in a 42-year-old woman with bronchiectasis. (a) CT scan obtained at the level of the ventricles shows patchy consolidation in the left lower lobe with multiple cystic lesions. Volume loss of the left lung is also noted. (b) CT scan shows the left inferior phrenic artery (arrow) originating at the level of the celiac axis and running anteriorly. (c) CT scan obtained at a higher level than in b shows the left inferior phrenic artery running anteriorly (arrow). (d) CT scan obtained at the level of the dome of the liver shows the enlarged left inferior phrenic artery (arrows). Left pleural thickening is also noted. (e) Coronal maximum-intensity projection image shows the left inferior phrenic artery arising from the celiac axis and supplying the left lower lobe.
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Figure 4b. Pseudosequestration in a 42-year-old woman with bronchiectasis. (a) CT scan obtained at the level of the ventricles shows patchy consolidation in the left lower lobe with multiple cystic lesions. Volume loss of the left lung is also noted. (b) CT scan shows the left inferior phrenic artery (arrow) originating at the level of the celiac axis and running anteriorly. (c) CT scan obtained at a higher level than in b shows the left inferior phrenic artery running anteriorly (arrow). (d) CT scan obtained at the level of the dome of the liver shows the enlarged left inferior phrenic artery (arrows). Left pleural thickening is also noted. (e) Coronal maximum-intensity projection image shows the left inferior phrenic artery arising from the celiac axis and supplying the left lower lobe.
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Figure 4c. Pseudosequestration in a 42-year-old woman with bronchiectasis. (a) CT scan obtained at the level of the ventricles shows patchy consolidation in the left lower lobe with multiple cystic lesions. Volume loss of the left lung is also noted. (b) CT scan shows the left inferior phrenic artery (arrow) originating at the level of the celiac axis and running anteriorly. (c) CT scan obtained at a higher level than in b shows the left inferior phrenic artery running anteriorly (arrow). (d) CT scan obtained at the level of the dome of the liver shows the enlarged left inferior phrenic artery (arrows). Left pleural thickening is also noted. (e) Coronal maximum-intensity projection image shows the left inferior phrenic artery arising from the celiac axis and supplying the left lower lobe.
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Figure 4d. Pseudosequestration in a 42-year-old woman with bronchiectasis. (a) CT scan obtained at the level of the ventricles shows patchy consolidation in the left lower lobe with multiple cystic lesions. Volume loss of the left lung is also noted. (b) CT scan shows the left inferior phrenic artery (arrow) originating at the level of the celiac axis and running anteriorly. (c) CT scan obtained at a higher level than in b shows the left inferior phrenic artery running anteriorly (arrow). (d) CT scan obtained at the level of the dome of the liver shows the enlarged left inferior phrenic artery (arrows). Left pleural thickening is also noted. (e) Coronal maximum-intensity projection image shows the left inferior phrenic artery arising from the celiac axis and supplying the left lower lobe.
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Figure 4e. Pseudosequestration in a 42-year-old woman with bronchiectasis. (a) CT scan obtained at the level of the ventricles shows patchy consolidation in the left lower lobe with multiple cystic lesions. Volume loss of the left lung is also noted. (b) CT scan shows the left inferior phrenic artery (arrow) originating at the level of the celiac axis and running anteriorly. (c) CT scan obtained at a higher level than in b shows the left inferior phrenic artery running anteriorly (arrow). (d) CT scan obtained at the level of the dome of the liver shows the enlarged left inferior phrenic artery (arrows). Left pleural thickening is also noted. (e) Coronal maximum-intensity projection image shows the left inferior phrenic artery arising from the celiac axis and supplying the left lower lobe.
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It is presumed that chronically inflamed lung tissue may activate neovascularization from the systemic circulation. It may be difficult to distinguish bronchopulmonary sequestration from pseudosequestration before surgery. At angiography, sequestrations generally demonstrate a clearly anomalous vessel supplying the mass, whereas small branches of hypertrophied normal vessels supply pseudose questrations. Bronchopulmonary sequestrations should not be associated with a pleural blush, which is a clue to the diagnosis of pseudosequestration. In cases of sequestration, single abdominal arteries penetrate the lung via the pulmonary ligament before dividing, whereas pseudosequestrations have a tangle of anastomotic vessels, which are more prominent on the surface of the mass (5),(19),(20). In our patients with pseudosequestration, hypertrophied normal vessels were demonstrated on spiral CT scans, and these findings were consistent with the angiographic findings. In addition, a sequestration should demonstrate enhancement with contrast material at CT, whereas a pseudosequestration enhances only at the periphery of the lesion, if at all. Medical treatment results in regression of a number of systemic-pulmonary artery anastomoses in pseudosequestration, a result that does not occur in bronchopulmonary sequestration (19).
Angiography performed before surgery or interventional procedures can be helpful in locating and determining the extents of systemic-pulmonary artery anastomoses. However, in our experience, spiral CT can demonstrate the vascular structures and parenchymal changes and provide useful information to surgeons and interventional radiologists, with no need for invasive angiography.
Chronic Pulmonary Artery Obstruction
Takayasu arteritis often affects the pulmonary artery as well as the aorta and its branches. When the pulmonary artery pressure becomes diminished due to the pulmonary artery stenosis, the bronchial artery may enlarge to serve as a collateral vessel (21). The systemic-to-pulmonary artery communication in Takayasu arteritis can be demonstrated with thoracic angiography. At pulmonary angiography, the proximally occluded pulmonary vessels are opacified by the systemic-to-pulmonary artery shunt (21),(22). In our patient with Takayasu arteritis, the diameter of the pulmonary artery was decreased and a hypertrophied left inferior phrenic artery and hypertrophied bronchial artery were demonstrated at spiral CT. Thoracic and pulmonary angiography also demonstrated hypertrophied systemic vessels, as well as delayed opacification of the pulmonary artery by a systemic-to-pulmonary artery shunt (Fig 5). Thus, demonstration of a systemic-to-pulmonary artery shunt appears to be indicative of pulmonary artery involvement in Takayasu arteritis (21). This finding can be demonstrated without performance of invasive angiography.
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Figure 5a. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5b. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5c. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5d. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5e. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5f. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Figure 5g. Takayasu arteritis with pulmonary artery involvement in a 20-year-old man. (a) CT scan obtained at the level of the tracheal carina shows a hypertrophied right bronchial artery in the retrobronchial area (black arrow). The right internal mammary artery (white arrow) is also enlarged in comparison with the left internal mammary artery (arrowhead). The aortic wall is thickened, and the pulmonary arteries are relatively small. The dilated ascending aorta suggests aortic involvement by Takayasu arteritis. (b) CT scan obtained at the level of the dome of the liver shows a hypertrophied left inferior phrenic artery (arrow). The right internal mammary artery is also demonstrated in the anterior chest wall (arrowhead). (c) CT scan obtained at the level of the aortic arch vessels shows the hypertrophied right internal mammary artery (arrow). Note the thickening of the arch vessels (arrowheads). (d) Bronchial angiogram shows hypervascular staining in the right lung. (e) Selective left inferior phrenic arteriogram shows the hypertrophied left inferior phrenic artery supplying the left lower lung. (f) Selective right internal mammary arteriogram shows the hypertrophied right internal mammary artery (arrow) and pulmonary vessels opacified by the systemic-to-pulmonary artery shunt. (g) Pulmonary angiogram shows multiple perfusion defects corresponding to the areas of systemic arterial supply.
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Pulmonary Arteriovenous Malformation
A pulmonary arteriovenous malformation (AVM) leads to chronic hypoxemia and systemic emboli. Systemic arterial supply to a pulmonary AVM may be a preexisting condition precipitated by the relative ischemia induced by the shunt (23). The systemic arterial supply to the pulmonary AVM is usually a response to surgery, although systemic arterial supply in the absence of surgery has been reported (23),(24). In other cyanotic diseases, thoracotomy often incites transpleural arterial supply to the lungs from systemic vessels; the same mechanism may be involved in pulmonary AVMs. The systemic vessels are hypertrophied due to the chronic cyanosis.
Our patient with systemic arterial supply to a pulmonary AVM had hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome). On spiral CT scans, a hypertrophied bronchial artery and multiple vascular structures were noted within the lung parenchyma. A thoracic angiogram allowed identification of systemic supply to the lungs by hypertrophied systemic arteries, as well as early pulmonary venous drainage (Fig 6).
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Figure 6a. Systemic arterial supply to the right lung in a 20-year-old woman with hereditary hemorrhagic telangiectasia. She underwent a right-sided thoracotomy for an AVM in early childhood. However, afterward she had many episodes of hemoptysis. (a) CT scan obtained at the level of the tracheal carina shows multiple nodular areas of increased attenuation within the mediastinal soft tissue (arrows), which represent a hypertrophied right bronchial artery. (b) Spiral CT scan shows a collapsed right lower lobe and multiple vascular structures (arrows) with the same enhancement as the thoracic aorta. (c) Thoracic angiogram shows vascular staining from multiple vascular structures supplying the lung parenchyma and early pulmonary venous drainage from the systemic arteries. (d) Selective bronchial angiogram shows a hypertrophied bronchial artery (arrow) and vascular staining from the right bronchial artery. Pulmonary venous drainage is also demonstrated (arrowheads).
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Figure 6b. Systemic arterial supply to the right lung in a 20-year-old woman with hereditary hemorrhagic telangiectasia. She underwent a right-sided thoracotomy for an AVM in early childhood. However, afterward she had many episodes of hemoptysis. (a) CT scan obtained at the level of the tracheal carina shows multiple nodular areas of increased attenuation within the mediastinal soft tissue (arrows), which represent a hypertrophied right bronchial artery. (b) Spiral CT scan shows a collapsed right lower lobe and multiple vascular structures (arrows) with the same enhancement as the thoracic aorta. (c) Thoracic angiogram shows vascular staining from multiple vascular structures supplying the lung parenchyma and early pulmonary venous drainage from the systemic arteries. (d) Selective bronchial angiogram shows a hypertrophied bronchial artery (arrow) and vascular staining from the right bronchial artery. Pulmonary venous drainage is also demonstrated (arrowheads).
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Figure 6c. Systemic arterial supply to the right lung in a 20-year-old woman with hereditary hemorrhagic telangiectasia. She underwent a right-sided thoracotomy for an AVM in early childhood. However, afterward she had many episodes of hemoptysis. (a) CT scan obtained at the level of the tracheal carina shows multiple nodular areas of increased attenuation within the mediastinal soft tissue (arrows), which represent a hypertrophied right bronchial artery. (b) Spiral CT scan shows a collapsed right lower lobe and multiple vascular structures (arrows) with the same enhancement as the thoracic aorta. (c) Thoracic angiogram shows vascular staining from multiple vascular structures supplying the lung parenchyma and early pulmonary venous drainage from the systemic arteries. (d) Selective bronchial angiogram shows a hypertrophied bronchial artery (arrow) and vascular staining from the right bronchial artery. Pulmonary venous drainage is also demonstrated (arrowheads).
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Figure 6d. Systemic arterial supply to the right lung in a 20-year-old woman with hereditary hemorrhagic telangiectasia. She underwent a right-sided thoracotomy for an AVM in early childhood. However, afterward she had many episodes of hemoptysis. (a) CT scan obtained at the level of the tracheal carina shows multiple nodular areas of increased attenuation within the mediastinal soft tissue (arrows), which represent a hypertrophied right bronchial artery. (b) Spiral CT scan shows a collapsed right lower lobe and multiple vascular structures (arrows) with the same enhancement as the thoracic aorta. (c) Thoracic angiogram shows vascular staining from multiple vascular structures supplying the lung parenchyma and early pulmonary venous drainage from the systemic arteries. (d) Selective bronchial angiogram shows a hypertrophied bronchial artery (arrow) and vascular staining from the right bronchial artery. Pulmonary venous drainage is also demonstrated (arrowheads).
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Spiral CT with three-dimensional reconstruction has become the most reliable diagnostic tool for detection of pulmonary AVMs and preembolization mapping of the afferent vessels (25). However, in our experience, systemic arterial supply should not be overlooked in evaluation of pulmonary AVMs with spiral CT, especially in patients with recurrent hemoptysis after treatment of the pulmonary AVM.
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Aberrant Systemic Arteries
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Bronchopulmonary Sequestration
A pulmonary sequestration is generally defined as nonfunctioning lung tissue that is not in normal continuity with the tracheobronchial tree and that derives its blood supply from systemic vessels (26). The systemic artery, which is not related to a cardiac malformation, typically enters the lung via the pulmonary ligament and generally has an elastic wall resembling that of a pulmonary artery rather than that of a bronchial artery. The arterial distribution may be just to the sequestered lung or may include adjacent normal lung tissue. The anomalous artery is considered to be a persistent primitive aortic branch that originally supplied the developing lung bud. Atheromatous changes are commonly found in these arteries after infancy (1). The large systemic artery is usually 6–7 mm in diameter and arises from the lower tho-racic or upper abdominal aorta. In 15%–20% of cases, the arteries are multiple (26). The majority of the cases are of the intralobar type; only a few are extralobar.
Intralobar sequestrations account for 75% of all pulmonary sequestrations. An intralobar sequestration consists of an abnormal segment of lung tissue that shares the visceral pleural covering of an otherwise normal pulmonary lobe and that lacks a normal communication to the tracheobronchial tree, although variable amounts of air may be contained within the anomalous tissue (26),(27). Intralobar sequestrations almost always occur within the lower lobes and occur slightly more often in the left lung than in the right lung (27). The chief pathologic features are chronic inflammation, cystic changes, and fibrosis (26). The anomalous aortic branches that supply the lesion are characteristically located within the inferior pulmonary ligament. Most cases are drained by normal pulmonary veins into the left atrium (28).
Conventional CT reveals parenchymal lesions and demonstrates the anomalous systemic artery in up to 80% of cases after contrast material administration (29)–(32). Using spiral CT, we demonstrated anomalous systemic arteries in seven of eight patients with suspected pulmonary sequestration (Figs 7, 8). Because spiral CT providesCT angiograms and high-quality cross-sectional images in a single acquisition, spiral CT and CT angiography seem to be the procedures of choice for imaging patients with abnormal chest radiographs and clinical features suggestive of pulmonary sequestration (33).
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Figure 7a. Intralobar pulmonary sequestration in a 41-year-old woman. (a) Posteroanterior chest radiograph shows consolidation in the left lower lung (arrowheads). (b) Spiral CT scan shows an enhancing vascular structure (arrow) arising from the thoracic aorta. (c) CT scan obtained at the level of the dome of the liver shows consolidation in the left lower lobe and an enhancing tubular structure (arrow) in the area of consolidation. (d) Coronal maximum-intensity projection image shows an anomalous systemic artery arising from the thoracic descending aorta.
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Figure 7b. Intralobar pulmonary sequestration in a 41-year-old woman. (a) Posteroanterior chest radiograph shows consolidation in the left lower lung (arrowheads). (b) Spiral CT scan shows an enhancing vascular structure (arrow) arising from the thoracic aorta. (c) CT scan obtained at the level of the dome of the liver shows consolidation in the left lower lobe and an enhancing tubular structure (arrow) in the area of consolidation. (d) Coronal maximum-intensity projection image shows an anomalous systemic artery arising from the thoracic descending aorta.
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Figure 7c. Intralobar pulmonary sequestration in a 41-year-old woman. (a) Posteroanterior chest radiograph shows consolidation in the left lower lung (arrowheads). (b) Spiral CT scan shows an enhancing vascular structure (arrow) arising from the thoracic aorta. (c) CT scan obtained at the level of the dome of the liver shows consolidation in the left lower lobe and an enhancing tubular structure (arrow) in the area of consolidation. (d) Coronal maximum-intensity projection image shows an anomalous systemic artery arising from the thoracic descending aorta.
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Figure 7d. Intralobar pulmonary sequestration in a 41-year-old woman. (a) Posteroanterior chest radiograph shows consolidation in the left lower lung (arrowheads). (b) Spiral CT scan shows an enhancing vascular structure (arrow) arising from the thoracic aorta. (c) CT scan obtained at the level of the dome of the liver shows consolidation in the left lower lobe and an enhancing tubular structure (arrow) in the area of consolidation. (d) Coronal maximum-intensity projection image shows an anomalous systemic artery arising from the thoracic descending aorta.
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Figure 8a. Intralobar pulmonary sequestration in a 34-year-old woman. (a) CT scan (lung window) shows cystic masses with an air-fluid level. (b) Axial maximum-intensity projection image shows an anomalous systemic artery (arrow) originating from the thoracic aorta and supplying the right lower lobe. (c) Axial shaded-surface display image shows an anomalous systemic artery (arrow) supplying the right lower lobe. (d) Thoracic aortogram shows the anomalous systemic artery (arrow) traced to the right lower lung.
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Figure 8b. Intralobar pulmonary sequestration in a 34-year-old woman. (a) CT scan (lung window) shows cystic masses with an air-fluid level. (b) Axial maximum-intensity projection image shows an anomalous systemic artery (arrow) originating from the thoracic aorta and supplying the right lower lobe. (c) Axial shaded-surface display image shows an anomalous systemic artery (arrow) supplying the right lower lobe. (d) Thoracic aortogram shows the anomalous systemic artery (arrow) traced to the right lower lung.
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Figure 8c. Intralobar pulmonary sequestration in a 34-year-old woman. (a) CT scan (lung window) shows cystic masses with an air-fluid level. (b) Axial maximum-intensity projection image shows an anomalous systemic artery (arrow) originating from the thoracic aorta and supplying the right lower lobe. (c) Axial shaded-surface display image shows an anomalous systemic artery (arrow) supplying the right lower lobe. (d) Thoracic aortogram shows the anomalous systemic artery (arrow) traced to the right lower lung.
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Figure 8d. Intralobar pulmonary sequestration in a 34-year-old woman. (a) CT scan (lung window) shows cystic masses with an air-fluid level. (b) Axial maximum-intensity projection image shows an anomalous systemic artery (arrow) originating from the thoracic aorta and supplying the right lower lobe. (c) Axial shaded-surface display image shows an anomalous systemic artery (arrow) supplying the right lower lobe. (d) Thoracic aortogram shows the anomalous systemic artery (arrow) traced to the right lower lung.
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An extralobar sequestration consists of a discrete, accessory lobe of nonaerated lung tissue that is invested in its own pleural envelope (34). In most patients with extralobar sequestration (approximately 61%), the lesion is diagnosed in the first 6 months of life. About 10% of extralobar sequestrations are found incidentally in asymptomatic individuals (26),(35). An anomalous artery that arises directly from the thoracic or abdominal aorta typically supplies an extralobar sequestration. The venous drainage is usually systemic through the azygos and hemiazygos system or superior vena cava into the right atrium (26),(36). The anomalous systemic artery is sometimes not visualized on spiral CT scans because the feeding vessel is typically single and has a small diameter (34). The diagnosis can be confirmed by means of angiography, which shows the systemic arterial supply to the lesions. However, spiral CT can demonstrate a parenchymal lesion, which manifests as a homogeneous mass of soft-tissue attenuation, emphysematous change, or a cystic area (34).
Congenital Pulmonary Venolobar Syndrome
Congenital pulmonary venolobar syndrome consists of a number of components, each of which represents a distinctly different congenital anomaly of the thorax (37). The major or common components of congenital pulmonary venolobar syndrome include hypogenetic lung, partial anomalous pulmonary venous return, absence of a pulmonary artery, pulmonary sequestration, systemic arterialization of the lung without sequestration, absence of the inferior vena cava, and duplication of the diaphragm (37),(38).
On a frontal chest radiograph, an anomalous pulmonary vein that usually drains all or part of the right lung into the inferior vena cava just above or below the diaphragm produces an appearance resembling a scimitar. Thus, when hypogenetic lung and partial anomalous pulmonary venous return coexist, the condition is referred to as scimitar syndrome. Scimitar syndrome is almost exclusively a right-sided condition, with the anomalous vein being a pulmonary vein (Fig 9) (37)–(42).
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Figure 9a. Congenital pulmonary venolobar syndrome in an 18-year-old woman. (a) Posteroanterior chest radiograph shows a large anomalous pulmonary vein resembling a scimitar in the right lower lung (arrowheads), coursing toward the right hemidiaphragm. A small right lung and a dextroposed heart are also seen. (b) Right posterior oblique shaded-surface display image shows an anomalous pulmonary vein (arrow) draining into the inferior vena cava (*).
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Figure 9b. Congenital pulmonary venolobar syndrome in an 18-year-old woman. (a) Posteroanterior chest radiograph shows a large anomalous pulmonary vein resembling a scimitar in the right lower lung (arrowheads), coursing toward the right hemidiaphragm. A small right lung and a dextroposed heart are also seen. (b) Right posterior oblique shaded-surface display image shows an anomalous pulmonary vein (arrow) draining into the inferior vena cava (*).
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Systemic collateral circulation to the peripheral pulmonary arteries occurs in cases of absence of a pulmonary artery. Most often, systemic collateral arteries arise from the bronchial arteries (42). Transpleural systemic-pulmonary artery anastomoses also develop, including the intercostal artery (43). In scimitar syndrome, part of the hypogenetic lung or the entire hypogenetic lung may receive arterial blood supply from the thoracic or abdominal aorta and its branches. In some cases, the anomalous arteries supply an area of associated pulmonary sequestration; however, in most cases, the anomalous arteries supply only the hypogenetic lung tissue. A systemic artery arising from the lower thoracic or upper abdominal aorta or inferior phrenic artery supplies at least the basal part of the maldeveloped right lung (38)–(42).
Spiral CT is useful in the study of this anomaly because it helps confirm the diagnosis and thus invasive studies may not be necessary. CT also helps explain findings not well understood, demonstrates anomalous vessels, and may reveal associated malformations not suspected from the plain radiographs (44).
Normal Lung Parenchyma
An anomalous systemic artery may supply an area of otherwise normal lung tissue in the absence of congenital heart and lung disease. This condition differs from classic bronchopulmonary sequestration in that the involved lung tissue retains a normal connection to the bronchial tree, although some authors place this entity within the broad framework of pulmonary sequestration. In addition, absence of the interlobar artery distal to theorigin of the superior segmental artery is considered an important differential point from classic bronchopulmonary sequestration (45),(46). Venous return is via the large inferior pulmonary vein into the left atrium. No direct communications exist between the anomalous systemic artery and the veins of the basal segments. The basal segments of the left lower lobe are most often involved (45),(46).
Although the cause of systemic arterial supply to normal lung tissue is unknown, it is thought that persistence of an embryonic connection between the aorta and the pulmonary parenchyma leads to this anomaly (1),(45),(46).
Most adult patients are asymptomatic or have recurrent hemoptysis, whereas the most common clinical manifestation in pediatric patients is a cardiac murmur (45). In our experience, two of three patients were asymptomatic and one had recurrent hemoptysis.
At posteroanterior chest radiography, the anomalous systemic artery appears as an ill-defined nodular area of increased opacity in the medial aspect of the left lower lobe (Fig 10). Anomalous systemic arteries are also demonstrated on spiral CT scans. Spiral CT shows vascular structures with the same attenuation as the thoracic aorta in the left lower lobe. Spiral CT can also provide information about the morphology of the bronchial tree and the pulmonary parenchyma (eg, that the basal segments of the left lower lobe are normal). Another CT finding is absence of the interlobar artery distal to the origin of the superior segmental artery (45),(46). These CT findings make distinction from classic bronchopulmonary sequestration possible.
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Figure 10a. Incidentally detected systemic arterial supply to the left lower lobe in a 52-year-old man. (a) Posteroanterior chest radiograph shows a nodular area of increased opacity in the retrocardiac area (arrow). (b) Contrast material-enhanced CT scan shows an enhancing curvilinear structure in the left peribronchial area (arrow). (c) CT scan (lung window) shows that the vessels of the involved lung are hypertrophied in comparison with those of the contralateral lung.
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Figure 10b. Incidentally detected systemic arterial supply to the left lower lobe in a 52-year-old man. (a) Posteroanterior chest radiograph shows a nodular area of increased opacity in the retrocardiac area (arrow). (b) Contrast material-enhanced CT scan shows an enhancing curvilinear structure in the left peribronchial area (arrow). (c) CT scan (lung window) shows that the vessels of the involved lung are hypertrophied in comparison with those of the contralateral lung.
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Figure 10c. Incidentally detected systemic arterial supply to the left lower lobe in a 52-year-old man. (a) Posteroanterior chest radiograph shows a nodular area of increased opacity in the retrocardiac area (arrow). (b) Contrast material-enhanced CT scan shows an enhancing curvilinear structure in the left peribronchial area (arrow). (c) CT scan (lung window) shows that the vessels of the involved lung are hypertrophied in comparison with those of the contralateral lung.
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Magnetic resonance (MR) imaging can demonstrate an anomalous systemic artery as well as CT (Fig 11). However, with MR imaging, it would not be easy to determine confidently whether the lung tissue supplied by a systemic artery is normal. Therefore, spiral CT is a useful technique for diagnosis of systemic arterial supply to normal lung tissue without performance of invasive angiography.
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Figure 11a. Anomalous systemic arterial supply to normal lung parenchyma in a 27-year-old man with recurrent hemoptysis. (a) Thoracic aortogram shows an anomalous systemic artery supplying the basal segment of the left lower lobe. (b) Coronal T1-weighted MR image shows an anomalous systemic artery (arrow) arising from the thoracic aorta. (c) CT scan (lung window) shows hypertrophied vessels in the left lower lobe. The left lower lobe has ground-glass attenuation, which is presumably a result of hyperemia from systemic supply to the lung.
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Figure 11b. Anomalous systemic arterial supply to normal lung parenchyma in a 27-year-old man with recurrent hemoptysis. (a) Thoracic aortogram shows an anomalous systemic artery supplying the basal segment of the left lower lobe. (b) Coronal T1-weighted MR image shows an anomalous systemic artery (arrow) arising from the thoracic aorta. (c) CT scan (lung window) shows hypertrophied vessels in the left lower lobe. The left lower lobe has ground-glass attenuation, which is presumably a result of hyperemia from systemic supply to the lung.
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Figure 11c. Anomalous systemic arterial supply to normal lung parenchyma in a 27-year-old man with recurrent hemoptysis. (a) Thoracic aortogram shows an anomalous systemic artery supplying the basal segment of the left lower lobe. (b) Coronal T1-weighted MR image shows an anomalous systemic artery (arrow) arising from the thoracic aorta. (c) CT scan (lung window) shows hypertrophied vessels in the left lower lobe. The left lower lobe has ground-glass attenuation, which is presumably a result of hyperemia from systemic supply to the lung.
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Abstract
LEARNING OBJECTIVES FOR TEST...
