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Congenital and Acquired Pulmonary Artery Anomalies in the Adult: Radiologic Overview¹

¹ From the Department of Radiology, SDI UDIAT-CD, Institut Universitari Parc Taulí–UAB, Corporació Parc Taulí, Parc Taulí s/n, Sabadell 08208, Barcelona, Spain (E.C., X.G., J.R., J.M.M., J.P., C.M., D.G.); and Department of Radiology, Hospital de la Ribera, Alzira, Spain (Y.P.). Recipient of a Certificate of Merit award for an education exhibit at the 2004 RSNA Annual Meeting. Received April 7, 2005; revision requested May 17; revision received and accepted July 11. All authors have no financial relationships to disclose. Address correspondence to E.C. (e-mail: ecastaner{at}cspt.es).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

 
Various congenital and acquired anomalies may affect the pulmonary arteries in adult patients. Congenital anomalies (proximal interruption, anomalous origin of the left pulmonary artery [pulmonary artery sling], and idiopathic dilatation of the pulmonary trunk) are usually found incidentally at chest radiography or computed tomography (CT). Acquired anomalies include diffuse or focal enlargement of the arteries because of pulmonary hypertension, aneurysm, and intravascular pulmonary metastasis; decreased arterial diameter because of bronchial carcinoma, mediastinal fibrosis, and Takayasu arteritis; and intraluminal filling defects due to pulmonary thromboembolism and pulmonary artery sarcoma. An awareness of the radiologic manifestations of the disease entities and potential pulmonary artery complications secondary to infection or vasculitis may enable an early diagnosis. CT angiography is becoming the standard method for evaluating patients in whom the presence of pulmonary embolism is suspected. CT assessment of the extent of heart effects in patients with pulmonary hypertension and pulmonary embolism is particularly important because such effects largely determine the prognosis.

© RSNA, 2006

	LEARNING OBJECTIVES FOR TEST 2

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

 
After reading this article and taking the test, the reader will be able to:

• Identify congenital anomalies of the pulmonary arteries in the adult patient at radiography and CT.
  
• Describe the role of CT for the assessment of pulmonary artery abnormalities, possible causes, and effects on the right ventricle.
  
• Recognize potential complications of vascular disease or infection that affects the pulmonary arteries.
  

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

 
In the normal adult anatomy, the pulmonary trunk, or main pulmonary artery, may have a diameter as great as 28 mm. The main, left, and right pulmonary arteries are intrapericardial. The right pulmonary artery has a longer mediastinal course than the left, and it divides into two lobar branches at the root of the right lung. The left pulmonary artery courses over the left main bronchus and penetrates the root of the left lung, where the artery divides into two lobar branches (1). The right and left pulmonary arteries should be of approximately equal size, although the left pulmonary artery appears slightly larger in most subjects. The segmental arteries are always seen near the accompanying branches of the bronchial tree, and the subsegmental arteries are easily recognized as dichotomous divisions of the corresponding segmental artery.

Pulmonary arteries (main, lobar, segmental, and subsegmental) with a diameter greater than 0.5 mm are referred to as elastic pulmonary arteries. They course downward along the bronchi to the subsegmental level, and their diameters are similar to those of the adjacent airways (2). The function of the elastic arteries is similar to that of the aorta: to provide a distensible reservoir for ventricular ejection. The normal pulmonary circulation is a low-pressure system that has approximately one-tenth the flow resistance of the systemic circulation, as well as a high capacitance. Beyond the subsegmental bronchi, these vessels transition to muscular arteries, which accompany the peripheral airways downward to the level of the terminal bronchioles. As the smooth-muscle layer progressively thins, these arteries become arterioles (0.15–0.015 mm in diameter), which proceed along the respiratory bronchioles and alveolar ducts to eventually form a capillary network in the alveolar walls (2).

The primary pulmonary circulation comprises the entire venous return. A second vascular network, the bronchial circulation, draws approximately 1% of the systemic cardiac output and transmits blood at a pressure six times that of the pulmonary circulation (3). Normally, the bronchial circulation only supplies nutrients and is not involved in gas exchange. However, in certain pathologic conditions (eg, occlusion of a main pulmonary artery), the bronchial vessels do participate in blood oxygenation. The bronchial circulation responds with enlargement and hypertrophy to decreased pulmonary flow and ischemia (3); transpleural systemic collateral vessels (eg, intercostal arteries, internal mammary arteries) also may develop (4). The pulmonary and bronchial vascular networks communicate via several microvascular interconnections. There are also transpleural systemic–pulmonary artery anastomoses (3).

When the presence of a pulmonary artery anomaly is suspected on the basis of chest radiographic findings, computed tomography (CT) is invaluable for examining the pulmonary vessels. State-of-the-art CT scanners provide clear depiction of peripheral vessels. CT also has an advantage over angiography in that it allows the lung parenchyma and the heart to be evaluated at the same time as the vessels.

In this article, we review the features of various congenital and acquired anomalies of the pulmonary arteries, with an emphasis on their CT appearance and possible effects on the heart. We have classified these anomalies in the following four categories: congenital anomalies; abnormalities that cause diffuse or focal pulmonary artery enlargement; abnormalities that cause a decrease in pulmonary arterial diameter; and abnormal processes that cause intraluminal filling defects. This system of classification is somewhat oversimplified, with some overlap between categories, but it enables organization of the information in a way that we believe will facilitate understanding.

	Congenital Anomalies

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

 
Most congenital anomalies of the pulmonary arteries in adults are found incidentally on chest radiographs or CT scans.

Unilateral Proximal Interruption of Arteries
Proximal interruption of the right or left pulmonary artery is an uncommon developmental anomaly. The term interruption is used in preference to absence of a pulmonary artery, since the portion of the vessel that is in the lung is usually intact and patent (5). In proximal interruption, the pulmonary artery ends blindly at the hilum, and blood is supplied to the lung through collateral systemic vessels, mainly bronchial arteries but also transpleural branches of the intercostal, internal mammary, subclavian, and innominate arteries (5,6).

Interruption of the left pulmonary artery is usually associated with a right aortic arch and other congenital cardiovascular anomalies, most commonly tetralogy of Fallot. Right pulmonary artery interruption is more common than left, and it is an isolated finding in most instances (6).

Chest radiographs typically show a volume loss in the hemithorax, depicted as diaphragmatic elevation with shifting of the heart and mediastinum to the affected side (7) (Fig 1). The contralateral lung is hyperinflated and herniates into the smaller hemithorax. In patients with enlarged intercostal and transpleural arteries, fine linear opacities are seen at the periphery of the lung (5,6) (Fig 1).

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 1.  Asymptomatic unilateral proximal interruption of the right pulmonary artery in a 48-year-old man. The posteroanterior chest radiograph shows a small hemithorax, mediastinal shift (arrowheads), absence of the right pulmonary artery shadow (open arrow), and linear opacities that correspond to systemic collateral vessels (solid arrows) along the pleura and within the lung. This patient did not manifest pulmonary hypertension.

View larger version (102K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Unilateral proximal interruption of the right pulmonary artery in a 52-year-old woman with progressive shortness of breath and hemoptysis. (a) Contrast material–enhanced CT scan shows only the proximal portion of the right pulmonary artery (arrowhead) and enlargement of the main and left pulmonary arteries that indicates pulmonary hypertension. (b) Contrast-enhanced CT scan at the level of the upper lobes shows serrated thickening of the right pleura because of enlarged intercostal collateral vessels (arrowheads). (c) CT scan obtained with a lung window setting shows multiple linear opacities perpendicular to the pleural surface that correspond to transpleural systemic vessels (arrowheads).

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Unilateral proximal interruption of the right pulmonary artery in a 52-year-old woman with progressive shortness of breath and hemoptysis. (a) Contrast material–enhanced CT scan shows only the proximal portion of the right pulmonary artery (arrowhead) and enlargement of the main and left pulmonary arteries that indicates pulmonary hypertension. (b) Contrast-enhanced CT scan at the level of the upper lobes shows serrated thickening of the right pleura because of enlarged intercostal collateral vessels (arrowheads). (c) CT scan obtained with a lung window setting shows multiple linear opacities perpendicular to the pleural surface that correspond to transpleural systemic vessels (arrowheads).

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.  Unilateral proximal interruption of the right pulmonary artery in a 52-year-old woman with progressive shortness of breath and hemoptysis. (a) Contrast material–enhanced CT scan shows only the proximal portion of the right pulmonary artery (arrowhead) and enlargement of the main and left pulmonary arteries that indicates pulmonary hypertension. (b) Contrast-enhanced CT scan at the level of the upper lobes shows serrated thickening of the right pleura because of enlarged intercostal collateral vessels (arrowheads). (c) CT scan obtained with a lung window setting shows multiple linear opacities perpendicular to the pleural surface that correspond to transpleural systemic vessels (arrowheads).

Pulmonary hypertension affects 19%–25% of patients with pulmonary artery interruption (Fig 2a) and is the most important determinant of the prognosis (8). In the differential diagnosis, acquired causes of pulmonary obstruction (chronic thromboembolic occlusion, Takayasu arteritis, and mediastinal fibrosis) must be ruled out.

On radiographs of patients with proximal interruption of a pulmonary artery, the affected lung is often as opaque as, or slightly more opaque than, the contralateral lung (Fig 1), and there is no evidence of air trapping at expiration. These findings help differentiate proximal interruption from Swyer-James syndrome (10). In patients with proximal interruption of a pulmonary artery, the bronchial branching pattern is normal, and this finding enables the exclusion of hypogenetic lung syndrome. A definitive diagnosis of proximal interruption of a pulmonary artery can be achieved with CT.

Anomalous Origin: Left Pulmonary Artery Sling
In this rare vascular developmental anomaly, the left pulmonary artery arises from the posterior aspect of the right pulmonary artery and passes between the trachea and esophagus to reach the left hilum (Fig 3). The left pulmonary artery thus forms a sling around the distal trachea and the proximal right main bronchus (11). Those affected by pulmonary artery sling may be classified generally into two groups: one with a normal bronchial pattern and the other with one or more malformations of the bronchotracheal tree (eg, stenosis of a long segment of the trachea or absence of the pars membranacea) as well as cardiovascular abnormalities. In the latter group, mortality and morbidity are high during infancy (11). The former group includes very few asymptomatic adults. In asymptomatic cases, a pulmonary artery sling may mimic a mediastinal mass on chest radiographs (Fig 4a). CT (Fig 4b) and magnetic resonance (MR) imaging (Fig 4c) may be used to establish the diagnosis with certainty (12).

View larger version (48K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Diagram shows the anomalous origin of a left pulmonary artery (P.A.) that arises from the posterior aspect of the right pulmonary artery and reaches the left hilum by passing between the trachea and the esophagus.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Anomalous origin of the left pulmonary artery in a 60-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an anomalous right paratracheal border (arrowheads). (b, c) Unenhanced CT scan (b) and MR angiogram (c) at the level of the pulmonary trunk show the abnormal course of the left pulmonary artery (arrowheads in b) between the lower portion of the trachea and the esophagus (* in b). (Fig 4b and 4c reprinted, with permission, from reference 12.)

View larger version (97K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Anomalous origin of the left pulmonary artery in a 60-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an anomalous right paratracheal border (arrowheads). (b, c) Unenhanced CT scan (b) and MR angiogram (c) at the level of the pulmonary trunk show the abnormal course of the left pulmonary artery (arrowheads in b) between the lower portion of the trachea and the esophagus (* in b). (Fig 4b and 4c reprinted, with permission, from reference 12.)

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.  Anomalous origin of the left pulmonary artery in a 60-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an anomalous right paratracheal border (arrowheads). (b, c) Unenhanced CT scan (b) and MR angiogram (c) at the level of the pulmonary trunk show the abnormal course of the left pulmonary artery (arrowheads in b) between the lower portion of the trachea and the esophagus (* in b). (Fig 4b and 4c reprinted, with permission, from reference 12.)

Patients are asymptomatic, and the anomaly is usually detected fortuitously on chest radiographs or CT scans (13). On chest radiographs, the enlargement of the main pulmonary artery causes a rounded bulge that simulates a mass in the left mediastinal border (Fig 5a). A definitive diagnosis may be achieved with the use of contrast-enhanced CT (Fig 5b, 5c) or MR imaging in combination with echocardiography (14).

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.  Idiopathic dilatation of the pulmonary trunk in a 55-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an abnormal bulge in the left mediastinal border (arrowheads), a feature suggestive of a mediastinal mass identical to that observed on radiographs obtained 6 years earlier (not shown). (b) Contrast-enhanced CT scan shows abnormal enlargement of the main pulmonary trunk, with mild dilatation of the right and left pulmonary arteries. (c) CT scan obtained with a lung window setting at the same level as b shows normal vessels and parenchyma.

View larger version (82K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.  Idiopathic dilatation of the pulmonary trunk in a 55-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an abnormal bulge in the left mediastinal border (arrowheads), a feature suggestive of a mediastinal mass identical to that observed on radiographs obtained 6 years earlier (not shown). (b) Contrast-enhanced CT scan shows abnormal enlargement of the main pulmonary trunk, with mild dilatation of the right and left pulmonary arteries. (c) CT scan obtained with a lung window setting at the same level as b shows normal vessels and parenchyma.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.  Idiopathic dilatation of the pulmonary trunk in a 55-year-old asymptomatic woman. (a) Posteroanterior chest radiograph shows an abnormal bulge in the left mediastinal border (arrowheads), a feature suggestive of a mediastinal mass identical to that observed on radiographs obtained 6 years earlier (not shown). (b) Contrast-enhanced CT scan shows abnormal enlargement of the main pulmonary trunk, with mild dilatation of the right and left pulmonary arteries. (c) CT scan obtained with a lung window setting at the same level as b shows normal vessels and parenchyma.

	Increased Arterial Diameter

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

Pulmonary Hypertension
Pulmonary hypertension is defined as a mean pulmonary artery pressure greater than 25 mm Hg during rest (normal level, 10 mm Hg) or greater than 30 mm Hg during exercise (normal level, 15 mm Hg), as determined with right heart catheterization (2). Pulmonary hypertension secondary to known cardiac, pulmonary, or hepatic disease is far more common than is primary pulmonary hypertension, which has no identifiable cause (2).

In accordance with the established classification system used by pathologists, pulmonary hypertension may be categorized as either precapillary (with changes limited to the pulmonary arterial circulation, mainly at the level of the muscular arteries) or postcapillary (with findings located within the pulmonary venous circulation, between the capillary bed and the left atrium) (2). We use this approach to explain the radiologic findings of pulmonary hypertension. Primary pulmonary hypertension is an idiopathic condition at the precapillary level, and its postcapillary counterpart is pulmonary veno-occlusive disease, a rare idiopathic condition (2).

Hypoxic lung disease (including chronic air-flow obstruction, fibrosis, and ventilatory failure due to primary chest wall dysfunction) is the most common cause of pulmonary hypertension in clinical practice, and it is precapillary in origin (17).

Precapillary pulmonary hypertension also may be associated with connective tissue disorders, particularly in patients with scleroderma and the so-called CREST (calcinosis, Raynaud phenomenon, esophageal motility disorders, sclerodactyly, and telangiectasia) syndrome (18). An increased incidence of pulmonary hypertension, six to 12 times the frequency in the general population, has been observed in patients with human immunodeficiency virus (HIV) infection (Fig 6). In the settings of HIV infection and connective tissue disorders, pathologic changes are similar to those in primary pulmonary hypertension. Other causes of precapillary pulmonary hypertension include long-standing left-to-right shunt, chronic thromboembolic disease, in situ pulmonary arterial thrombotic disease (eg, polycythemia, sickle-cell disease), and widespread pulmonary embolism arising from intravascular malignant cells, parasites, or foreign materials (2).

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Pulmonary hypertension in a 32-year-old woman with HIV infection. (a) Posteroanterior chest radiograph shows enlargement of the main pulmonary artery (arrowheads). (b) Contrast-enhanced CT scan shows an enlarged pulmonary trunk with a maximum diameter of 39 mm (black line) near its bifurcation, lateral to the ascending aorta—a diameter greater than that of the ascending aorta.

View larger version (57K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Pulmonary hypertension in a 32-year-old woman with HIV infection. (a) Posteroanterior chest radiograph shows enlargement of the main pulmonary artery (arrowheads). (b) Contrast-enhanced CT scan shows an enlarged pulmonary trunk with a maximum diameter of 39 mm (black line) near its bifurcation, lateral to the ascending aorta—a diameter greater than that of the ascending aorta.

Because the clinical findings are nonspecific, pulmonary hypertension often is not recognized until it has reached an advanced stage. The increase in pulmonary blood pressure leads to remodeling of the pulmonary arteries and to right heart insufficiency; progression to right heart in-sufficiency is associated with a poor prognosis (20). Evaluation with CT can contribute to the care of patients with pulmonary hypertension by helping to detect the presence of the condition, indicating its possible causes (lung parenchymal disease or primary cardiac process, chronic thromboembolic disease), and depicting the state of the right ventricle (21).

Vascular Signs at CT.— Increased vascular resistance leads to dilatation of the central pulmonary arteries. The presence of pulmonary hypertension should be suspected when the diameter of the main pulmonary artery on CT scans is greater than 29 mm (2). The CT diameter of the main pulmonary artery is measured in the scanning plane of its bifurcation, at a right angle to its long axis and just lateral to the ascending aorta (Fig 6b). The finding of a diameter of 29 mm or greater has a sensitivity of 87% and specificity of 89% for a diagnosis of pulmonary hypertension (2). If this finding is associated with a segmental artery-to-bronchus ratio greater than one of three lobes, the specificity for the diagnosis of pulmonary hypertension increases to 100% (22) (Fig 7). When the ratio of the diameter of the main pulmonary artery to the diameter of the aorta is greater than 1:1, as determined on the basis of CT scans, a strong correlation with elevated pulmonary artery pressure also has been shown, especially in patients younger than 50 years (23) (Fig 6b). The diameters of the left and right pulmonary arteries (normal upper limit, 16 mm) appear to be poorer indicators of the presence of pulmonary hypertension (1,24).

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 7.  Pulmonary hypertension. CT scan obtained with a lung window setting at the level of the upper lobes in a 75-year-old man shows marked enlargement of the pulmonary arteries (arrowheads) in relation to the bronchi.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 8.  Pulmonary hypertension. CT scan obtained with a lung window setting in a 65-year-old woman shows a mosaic perfusion pattern, with increased diameters of vessels in areas of hyperattenuation (arrows) and sharp tapering of peripheral vessels in areas of hypoattenuation (arrowheads).

The bronchial circulation responds to decreased pulmonary flow and ischemia with enlargement and hypertrophy (3). Abnormal enlargement (to a diameter of more than 1.5 mm) of bronchial systemic arteries occurs with a higher frequency in patients who have chronic thromboembolic pulmonary hypertension (Fig 9) than in patients who have primary pulmonary hypertension (27). The finding of abnormal enlargement therefore may be useful for distinguishing between these two entities.

View larger version (69K): [in this window] [in a new window] [Download PPT slide]   Figure 9.  Chronic thromboembolic pulmonary hypertension in a 62-year-old man with dyspnea. Contrast-enhanced CT scan shows enlargement of left (black arrowhead) and right (white arrowhead) bronchial arteries, as well as filling defects in the right upper lobe pulmonary vessels (arrows) that correspond to new locations of acute pulmonary thromboembolism.

View larger version (90K): [in this window] [in a new window] [Download PPT slide]   Figure 10.  Pulmonary hypertension in a 72-year-old man with a mitral valve abnormality. Unenhanced CT scan shows dilatation and atherosclerotic calcification of the main and right pulmonary arteries (black arrowheads) and the left interlobar artery (white arrowhead).

Mosaic lung attenuation is seen more often in patients who have pulmonary hypertension due to vascular disease than in those with pulmonary hypertension due to cardiac or lung disease. Chronic pulmonary thromboembolism is the most common disease responsible for a finding of mosaic attenuation (29), and that finding is probably due to an uneven distribution of emboli and, subsequently, sequelae within the lungs.

Mediastinal and Cardiac Signs.— Helical CT, particularly when performed with the use of multidetector technology and cardiac gating, allows evaluation of right ventricular function in patients with pulmonary hypertension. Right heart disease is a common and expected secondary finding of pulmonary hypertension; the increased workload borne by the right heart results in right-sided cardiac enlargement and hypertrophy. Dilatation of the right ventricle is considered present when the ratio of the diameter of the right ventricle to that of the left ventricle is greater than 1:1 and there is bowing of the interventricular septum toward the left ventricle (30) (Fig 11a). The minor axes of the right and left ventricular chambers can be measured in the axial plane at their widest points, in diastole, between the inner surface of the free wall and the surface of the interventricular septum. The diastolic maxima of the right and left ventricles may be reached at slightly different levels. Recently, various investigators (31,32) using multidetector CT scanners found that ventricular measurements based on four-chamber views obtained with two-dimensional reconstructions were superior to those based on axial views and more comparable than the latter to those based on echocardiograms.

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  Right heart abnormalities secondary to pulmonary hypertension in a 56-year-old woman. (a) Contrast-enhanced CT scan shows dilatation of the right ventricle (RV), with a right ventricle/left ventricle (LV) ratio greater than 1:1; leftward septal bowing (arrowhead); thickening of the free right ventricular wall (arrow); and dilatation of the right atrium (RA). (b) Contrast-enhanced CT scan at a lower level than a shows dilatation of the right ventricle (RV) and inferior vena cava (IVC), as well as a small pericardial effusion (*).

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  Right heart abnormalities secondary to pulmonary hypertension in a 56-year-old woman. (a) Contrast-enhanced CT scan shows dilatation of the right ventricle (RV), with a right ventricle/left ventricle (LV) ratio greater than 1:1; leftward septal bowing (arrowhead); thickening of the free right ventricular wall (arrow); and dilatation of the right atrium (RA). (b) Contrast-enhanced CT scan at a lower level than a shows dilatation of the right ventricle (RV) and inferior vena cava (IVC), as well as a small pericardial effusion (*).

Elevated right heart pressures may cause a reflux of hyperdense contrast material into the inferior vena cava and hepatic veins (Fig 12). This finding can be seen in right heart failure, constrictive pericarditis, pulmonary hypertension, and tricuspid regurgitation. In a recent article, Yeh et al (33) suggested that the rate of the contrast material injection contributes to the frequency of findings of reflux. The usefulness of this classic sign as an indicator of right-sided heart disease diminishes with high injection rates (more than 3 mL/sec).

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 12.  Severe pulmonary hypertension and right heart disease in a 75-year-old patient. CT scan shows opacification of the inferior vena cava and suprahepatic veins because of retrograde flow of contrast material, which is often seen in patients with elevated right atrial and right ventricular pressures.

The presence of adenopathy in association with septal lines and ground-glass opacities is suggestive of pulmonary veno-occlusive disease (35).

Pulmonary Artery Aneurysm
Aneurysms or pseudoaneurysms of the pulmonary arteries, whether congenital or acquired, are rare. They may occur in association with a congenital cardiovascular anomaly, especially patent ductus arteriosus; infection (mycotic aneurysm); trauma, most commonly as a result of pulmonary artery perforation (due to improper placement of a catheter) or penetrating injury and very rarely as a result of blunt injury; vascular abnormality (eg, cystic medial necrosis, Behçet disease, Marfan syndrome, and Takayasu disease); and pulmonary hypertension (36).

In appropriate clinical settings, an aneurysm or pseudoaneurysm should be suspected in patients who present with hemoptysis or in whom chest radiography shows hilar enlargement or a new focal lung mass that has stable or increased size at subsequent radiographic examination (21). Early diagnosis is crucial; the mortality rate for patients with a ruptured pulmonary artery aneurysm is 100% (37). Helical CT is considered the noninvasive imaging modality of choice for the work-up of patients suspected of having pulmonary artery aneurysm, prior to therapeutic interventions (embolization or surgery). Contrast-enhanced CT allows assessment of the presence, size, and location of the aneurysm; aneurysms appear as saccular or fusiform areas of dilatation, with homogeneous contrast material filling that occurs simultaneously with that in the pulmonary artery.

Behçet Disease.— Behçet disease, a chronic inflammatory disorder of unknown origin, is characterized by recurrent oral and genital ulcerations, ocular anomalies, and additional clinical manifestations in multiple organ systems. It is now recognized to be a systemic vasculitis that may involve arteries and veins of any size (38). An arterial lesion may develop in the aorta or the main pulmonary artery and its major branches. The lesion manifests as an aneurysm in 65% of patients and as occlusion in 35% (39). Pulmonary artery aneurysms are associated with a poor prognosis; 30% of patients die within 2 years after diagnosis (38). Aneurysms may be single or multiple, and they most commonly involve the central pulmonary arteries (Fig 13). On a chest radiograph, a hilar enlargement or a round perihilar opacity may suggest the presence of an aneurysm; on CT scans, a mural thrombus is frequently observed in pulmonary artery aneurysms (Fig 13) and is usually due to in situ thrombosis (40).

View larger version (63K): [in this window] [in a new window] [Download PPT slide]   Figure 13.  Pulmonary artery aneurysm in a 50-year-old man with Behçet disease and hemoptysis. Contrast-enhanced CT scan shows aneurysmal dilatation of a left interlobar pulmonary artery (*) with small mural thrombi (arrowheads).

View larger version (72K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.  Septic emboli in a 20-year-old woman with osteomyelitis and hemoptysis. (a) CT scan at the level of the lower lobes shows an enhancing round lung mass with attenuation similar to that of central arteries (not shown), findings that indicate an aneurysm in the right lower lobe artery (*). Peripheral triangular opacities in the left lung and a bilateral pleural effusion also are visible. (b) CT scan obtained with a lung window setting shows a cavitated peripheral nodule in the right lung (arrowhead), enlargement of a right interlobular artery, and right-sided pneumothorax (*) due to cavitary lesions. (c) MR angiogram shows the right lower lobe pulmonary artery aneurysm. A right lower lobectomy was performed.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.  Septic emboli in a 20-year-old woman with osteomyelitis and hemoptysis. (a) CT scan at the level of the lower lobes shows an enhancing round lung mass with attenuation similar to that of central arteries (not shown), findings that indicate an aneurysm in the right lower lobe artery (*). Peripheral triangular opacities in the left lung and a bilateral pleural effusion also are visible. (b) CT scan obtained with a lung window setting shows a cavitated peripheral nodule in the right lung (arrowhead), enlargement of a right interlobular artery, and right-sided pneumothorax (*) due to cavitary lesions. (c) MR angiogram shows the right lower lobe pulmonary artery aneurysm. A right lower lobectomy was performed.

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 14c.  Septic emboli in a 20-year-old woman with osteomyelitis and hemoptysis. (a) CT scan at the level of the lower lobes shows an enhancing round lung mass with attenuation similar to that of central arteries (not shown), findings that indicate an aneurysm in the right lower lobe artery (*). Peripheral triangular opacities in the left lung and a bilateral pleural effusion also are visible. (b) CT scan obtained with a lung window setting shows a cavitated peripheral nodule in the right lung (arrowhead), enlargement of a right interlobular artery, and right-sided pneumothorax (*) due to cavitary lesions. (c) MR angiogram shows the right lower lobe pulmonary artery aneurysm. A right lower lobectomy was performed.

View larger version (73K): [in this window] [in a new window] [Download PPT slide]   Figure 15a.  Rasmussen aneurysm in a 42-year-old man with active postprimary tuberculosis and massive hemoptysis. (a) Contrast-enhanced CT scan at the level of the upper lobes shows, in an area of cavitation, a small rounded bilobed enhancing lesion (arrows) that arises from a branch of the pulmonary artery (arrowhead). (b) Conventional angiogram shows contrast material filling two aneurysms (arrowheads) in a segmental branch of the right upper lobe pulmonary artery. (c) Posteroanterior chest radiograph obtained after embolization shows coils (arrowheads) in the wall of the tuberculous cavity.

View larger version (167K): [in this window] [in a new window] [Download PPT slide]   Figure 15b.  Rasmussen aneurysm in a 42-year-old man with active postprimary tuberculosis and massive hemoptysis. (a) Contrast-enhanced CT scan at the level of the upper lobes shows, in an area of cavitation, a small rounded bilobed enhancing lesion (arrows) that arises from a branch of the pulmonary artery (arrowhead). (b) Conventional angiogram shows contrast material filling two aneurysms (arrowheads) in a segmental branch of the right upper lobe pulmonary artery. (c) Posteroanterior chest radiograph obtained after embolization shows coils (arrowheads) in the wall of the tuberculous cavity.

View larger version (185K): [in this window] [in a new window] [Download PPT slide]   Figure 15c.  Rasmussen aneurysm in a 42-year-old man with active postprimary tuberculosis and massive hemoptysis. (a) Contrast-enhanced CT scan at the level of the upper lobes shows, in an area of cavitation, a small rounded bilobed enhancing lesion (arrows) that arises from a branch of the pulmonary artery (arrowhead). (b) Conventional angiogram shows contrast material filling two aneurysms (arrowheads) in a segmental branch of the right upper lobe pulmonary artery. (c) Posteroanterior chest radiograph obtained after embolization shows coils (arrowheads) in the wall of the tuberculous cavity.

Tumor embolization in the pulmonary arteries may be manifested by various patterns on CT scans, depending on the size of the vessels affected. Large emboli in the main, lobar, and segmental pulmonary arteries cause filling defects that mimic acute pulmonary thromboembolism. Small tumor emboli that affect subsegmental arteries produce multifocal dilatation or beading of vessels (46) (Fig 16), whereas tumor emboli that affect secondary pulmonary lobule arterioles have a tree-in-bud appearance (47).

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 16.  Metastatic intravascular emboli in a 55-year-old man with renal cell carcinoma. CT scan obtained with a lung window setting shows vascular dilatation and beading of subsegmental arteries (arrowheads), findings highly suggestive of metastatic intravascular emboli.

	Decreased Arterial Diameter

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

Bronchial Carcinoma
CT plays a major role in determining the potential surgical resectability of the tumor and the type of surgery. Tumors that encase or surround the main pulmonary artery or the proximal right or left pulmonary artery, or that extend around more than 180° of the arterial circumference, are unresectable (48) (Fig 17). If more distal parts of the right and left pulmonary arteries are involved, a complete resection may be possible, but this requires pneumonectomy.

View larger version (63K): [in this window] [in a new window] [Download PPT slide]   Figure 17.  Unresectable bronchial carcinoma in a 30-year-old man. Contrast-enhanced CT scan shows extensive mediastinal tumor infiltration with obliteration of fat planes and encasement of the left pulmonary artery.

There are two types of mediastinal fibrosis: focal and diffuse. The focal type typically appears as a localized calcified mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila on CT scans (Fig 18). The focal type is probably caused by an idiosyncratic fibroinflammatory reaction to previous histoplasmosis or tuberculosis. The diffuse type manifests on CT scans as a diffusely infiltrative noncalcified mass that affects multiple mediastinal compartments. This type often occurs in association with autoimmune disorders, retroperitoneal fibrosis, sclerosing thyroiditis, and certain drugs; occasionally, it is idiopathic (51).

View larger version (99K): [in this window] [in a new window] [Download PPT slide]   Figure 18a.  Focal mediastinal fibrosis secondary to tuberculosis in a 62-year-old man. (a) Unenhanced CT scan at the level of the right hilum shows a highly calcified mass that encases the right pulmonary artery (curved arrow) and involves the left lower lobe vein (straight arrow) and left atrium (not shown). (b) CT scan obtained with a lung window setting shows multiple linear opacities perpendicular to the pleural surface (black arrowhead), enlarged septa (white arrowhead) due to systemic supply by collateral vessels (secondary to involvement of the right pulmonary artery), and enlarged septal veins (secondary to involvement of the left lower lobe vein). Note the striking contrast in appearance between the right and left lungs.

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 18b.  Focal mediastinal fibrosis secondary to tuberculosis in a 62-year-old man. (a) Unenhanced CT scan at the level of the right hilum shows a highly calcified mass that encases the right pulmonary artery (curved arrow) and involves the left lower lobe vein (straight arrow) and left atrium (not shown). (b) CT scan obtained with a lung window setting shows multiple linear opacities perpendicular to the pleural surface (black arrowhead), enlarged septa (white arrowhead) due to systemic supply by collateral vessels (secondary to involvement of the right pulmonary artery), and enlarged septal veins (secondary to involvement of the left lower lobe vein). Note the striking contrast in appearance between the right and left lungs.

Takayasu Arteritis
Takayasu arteritis is an idiopathic arteritis that mainly affects the elastic arteries. Frequently, it affects the aorta and its major branches; less commonly, it may affect the pulmonary arteries (52). It is most commonly seen in young Asian women. Pulmonary artery involvement occurs in 50%–80% of patients and is often a late manifestation of the disease. The most characteristic findings are stenosis or occlusion, mainly of the segmental and subsegmental arteries and less commonly of the lobar or main pulmonary arteries (52).

CT angiography has a high diagnostic accuracy and clearly depicts both luminal and mural changes. CT manifestations of pulmonary artery involvement include wall thickening and enhancement in early phases and mural calcium deposition and luminal stenosis or occlusion in chronic phases. The presence of mural enhancement is suggestive of active disease (53). Unilateral occlusion of a pulmonary artery can occur in advanced cases (Fig 19), and late-phase Takayasu arteritis should be considered in cases of chronic pulmonary artery obstruction of unknown origin (52). As in other situations of decreased pulmonary flow, collateral vessels may develop (Fig 19b, 19c).

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 19a.  Late-stage Takayasu arteritis with right pulmonary artery involvement in a 63-year-old woman. (a) Unenhanced CT scan shows marked stenosis of the right pulmonary artery (arrowheads), left-sided pulmonary hypertension, and wall calcification of the left pulmonary artery and the ascending and descending aorta. (b) Contrast-enhanced CT scan at the level of the supraaortic trunks shows soft tissue that surrounds the brachiocephalic trunk (straight arrows), occlusion of the left carotid artery (curved arrow), poor visibility of vessels in the right lung because of right pulmonary artery involvement, and collateral vessel development from intercostal arteries (arrowheads). (c) Contrast-enhanced CT scan shows right pulmonary artery occlusion (straight arrow), enlarged bronchial arteries (curved arrow) in the right hilum, and an enlarged right internal mammary artery (arrowhead). (Case courtesy of Jordi Andreu, MD, Hospital Vall de Hebron, Barcelona, Spain.)

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 19b.  Late-stage Takayasu arteritis with right pulmonary artery involvement in a 63-year-old woman. (a) Unenhanced CT scan shows marked stenosis of the right pulmonary artery (arrowheads), left-sided pulmonary hypertension, and wall calcification of the left pulmonary artery and the ascending and descending aorta. (b) Contrast-enhanced CT scan at the level of the supraaortic trunks shows soft tissue that surrounds the brachiocephalic trunk (straight arrows), occlusion of the left carotid artery (curved arrow), poor visibility of vessels in the right lung because of right pulmonary artery involvement, and collateral vessel development from intercostal arteries (arrowheads). (c) Contrast-enhanced CT scan shows right pulmonary artery occlusion (straight arrow), enlarged bronchial arteries (curved arrow) in the right hilum, and an enlarged right internal mammary artery (arrowhead). (Case courtesy of Jordi Andreu, MD, Hospital Vall de Hebron, Barcelona, Spain.)

View larger version (92K): [in this window] [in a new window] [Download PPT slide]   Figure 19c.  Late-stage Takayasu arteritis with right pulmonary artery involvement in a 63-year-old woman. (a) Unenhanced CT scan shows marked stenosis of the right pulmonary artery (arrowheads), left-sided pulmonary hypertension, and wall calcification of the left pulmonary artery and the ascending and descending aorta. (b) Contrast-enhanced CT scan at the level of the supraaortic trunks shows soft tissue that surrounds the brachiocephalic trunk (straight arrows), occlusion of the left carotid artery (curved arrow), poor visibility of vessels in the right lung because of right pulmonary artery involvement, and collateral vessel development from intercostal arteries (arrowheads). (c) Contrast-enhanced CT scan shows right pulmonary artery occlusion (straight arrow), enlarged bronchial arteries (curved arrow) in the right hilum, and an enlarged right internal mammary artery (arrowhead). (Case courtesy of Jordi Andreu, MD, Hospital Vall de Hebron, Barcelona, Spain.)

	Filling Defects

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

A primary pulmonary artery sarcoma is a very uncommon cause of an intraluminal arterial defect.

Pulmonary Thromboembolism
Acute Pulmonary Embolism.— CT pulmonary angiography is becoming the standard of care at many institutions for the evaluation of patients with suspected pulmonary embolism because it is rapid, noninvasive, and readily available and because it often helps provide an alternative diagnosis (55,56). The development of multidetector CT has led to improved visualization of peripheral pulmonary arteries and small subsegmental emboli (57).

The CT diagnostic criteria for this condition are the following: (a) a complete filling defect, with failure to enhance the entire lumen and possibly with enlargement of the occluded artery in comparison with adjacent patent vessels (Fig 20); (b) a partial filling defect surrounded by areas of contrast material enhancement, producing the "railway track" sign on longitudinal images of the vessel (Fig 21a); or (c) a peripheral filling defect that forms acute angles with the arterial wall (Fig 21a) (58).

View larger version (91K): [in this window] [in a new window] [Download PPT slide]   Figure 20.  Acute occlusive pulmonary thromboembolism in a 58-year-old woman. Contrast-enhanced CT scan shows enlargement of an occluded artery (arrowheads) in the left upper lobe compared with the diameters of adjacent patent vessels (arrow), as well as filling defects in the right upper lobe artery.

View larger version (80K): [in this window] [in a new window] [Download PPT slide]   Figure 21a.  Acute pulmonary thromboembolism in a 32-year-old woman with severe dyspnea. (a) Contrast-enhanced CT scan shows significant bilateral partial filling defects in peripheral segments of both interlobar arteries (arrowheads). In the right interlobar artery, the filling defect results in the "railway track" sign. In the left interlobar artery, the partial filling defect and surrounding area of contrast enhancement form acute angles with the arterial wall. (b) Contrast-enhanced CT scan at the level of the lower lobes shows peripheral triangular nonenhanced densities (arrows), suggestive of infarcts or hemorrhage, and some peripheral areas with enhancement (white arrowhead) suggestive of atelectasis. The short axis (black line) of the right ventricle (RV) is wider than that of the left ventricle (LV), and mild displacement of the interventricular septa (black arrowheads) is visible. These abnormalities suggest right ventricular strain.

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 21b.  Acute pulmonary thromboembolism in a 32-year-old woman with severe dyspnea. (a) Contrast-enhanced CT scan shows significant bilateral partial filling defects in peripheral segments of both interlobar arteries (arrowheads). In the right interlobar artery, the filling defect results in the "railway track" sign. In the left interlobar artery, the partial filling defect and surrounding area of contrast enhancement form acute angles with the arterial wall. (b) Contrast-enhanced CT scan at the level of the lower lobes shows peripheral triangular nonenhanced densities (arrows), suggestive of infarcts or hemorrhage, and some peripheral areas with enhancement (white arrowhead) suggestive of atelectasis. The short axis (black line) of the right ventricle (RV) is wider than that of the left ventricle (LV), and mild displacement of the interventricular septa (black arrowheads) is visible. These abnormalities suggest right ventricular strain.

An important potential use of CT is in the assessment of patients with severe acute pulmonary embolism by quantifying pulmonary arterial bed obstruction with various scores and by evaluating morphologic change in the heart (61).

CT pulmonary angiographic findings are typically reported as either positive or negative, with little or no mention made of the amount of thrombus present. One recent report (62) suggests that a pulmonary embolus index may have an important prognostic value, since patients with a pulmonary vascular obstruction of more than 60% tended to have a poor clinical outcome.

Patients with right ventricular dysfunction after pulmonary embolism have a higher mortality rate than those with normal right ventricular function, even if they are hemodynamically stable at presentation (63). Since these patients may require more aggressive treatment (eg, thrombolytic therapy), the detection of right ventricular dysfunction (defined as a ratio of more than 1:1 for comparison of the right ventricular minor axis diameter with the left ventricular minor axis diameter, and the presence of interventricular septal shift) (Fig 21b) may be useful for risk stratification (64).

In some cases, central pulmonary emboli are detectable on unenhanced CT scans as intraluminal areas of high attenuation. At unenhanced CT, such a finding may indicate that further imaging should be performed to exclude pulmonary embolism (65).

Chronic Pulmonary Thromboembolism.— Most pulmonary emboli resolve without sequelae. In a small percentage of patients, particularly those with large emboli or with recurrent episodes, incomplete resolution of thrombi occurs (60). The remaining embolic material is incorporated into the vessel wall and covered over by a thin layer of endothelial cells. The resultant vascular stenosis may lead to severe pulmonary hypertension and cor pulmonale, in which case surgical correction with thromboendarterectomy is the only treatment option (60). The best candidates for thromboendarterectomy are patients with central emboli and no peripheral disease. Helical CT may be helpful in the preoperative evaluation of these patients (66).

The CT diagnostic criteria include the following: (a) the presence of organized thromboembolic material (a peripheral flattened filling defect that forms obtuse angles with the arterial wall) and, occasionally, calcification of thrombi (Figs 22–24); (b) retracted thrombi (complete filling defect at the level of stenosed pulmonary arteries, with the appearance of an abrupt cutoff or narrowing of the vessel) (Fig 25a); or (c) recanalization of thrombi (with contrast material flowing through arteries with thickened walls and, often, smaller arteries, and with a weblike formation or flap appearing within the contrast material–filled artery) (Fig 25a) (58).

View larger version (64K): [in this window] [in a new window] [Download PPT slide]   Figure 22.  Chronic pulmonary embolism in a 62-year-old man with dyspnea (same patient as in Fig 9). Contrast-enhanced CT scan shows a large eccentric pulmonary embolus (arrowhead) in the left main pulmonary artery.

View larger version (71K): [in this window] [in a new window] [Download PPT slide]   Figure 23.  Chronic pulmonary embolism in a 72-year-old woman. Contrast-enhanced CT scan shows an eccentrically located small thrombus that forms obtuse angles with the vessel wall (arrowheads) in the right lower lobe.

View larger version (70K): [in this window] [in a new window] [Download PPT slide]   Figure 24a.  Chronic pulmonary embolism in a 78-year-old man. (a) Unenhanced CT scan shows calcification at the level of the right pulmonary artery (white arrowhead) and a hypoattenuating adjacent area (black arrowheads). Unlike acute pulmonary embolism, chronic pulmonary embolism may be indicated by hypoattenuating clots at unenhanced CT. (b) Contrast-enhanced CT scan shows a peripheral clot in the corresponding hypoattenuating area (arrowhead).

View larger version (68K): [in this window] [in a new window] [Download PPT slide]   Figure 24b.  Chronic pulmonary embolism in a 78-year-old man. (a) Unenhanced CT scan shows calcification at the level of the right pulmonary artery (white arrowhead) and a hypoattenuating adjacent area (black arrowheads). Unlike acute pulmonary embolism, chronic pulmonary embolism may be indicated by hypoattenuating clots at unenhanced CT. (b) Contrast-enhanced CT scan shows a peripheral clot in the corresponding hypoattenuating area (arrowhead).

View larger version (63K): [in this window] [in a new window] [Download PPT slide]   Figure 25a.  Chronic pulmonary artery obstruction in a 68-year-old woman with dyspnea. (a) Contrast-enhanced CT scan at the level of the left hilum shows retracted embolic material (arrow); a marked reduction in the diameter of the left lower lobe pulmonary artery; and contrast material in the central lumen, a finding suggestive of recanalization of the artery. (b) Contrast-enhanced CT scan at a level slightly higher than a shows enlargement of the bronchial arteries (arrowhead) because of a bronchial system–to–pulmonary system shunt. (c) Unenhanced CT scan obtained with a lung window setting at the level of the lower lobes shows marked stenosis of the left lower lobe arteries and dilatation of the accompanying bronchi (arrow); multiple linear opacities (arrowheads) adjacent to the pleural surface in the left lower lobe, suggestive of transpleural systemic vessels; marked dilatation of the vessels in the right lung; and a thrombus (*) in the right lower lobe artery.

View larger version (66K): [in this window] [in a new window] [Download PPT slide]   Figure 25b.  Chronic pulmonary artery obstruction in a 68-year-old woman with dyspnea. (a) Contrast-enhanced CT scan at the level of the left hilum shows retracted embolic material (arrow); a marked reduction in the diameter of the left lower lobe pulmonary artery; and contrast material in the central lumen, a finding suggestive of recanalization of the artery. (b) Contrast-enhanced CT scan at a level slightly higher than a shows enlargement of the bronchial arteries (arrowhead) because of a bronchial system–to–pulmonary system shunt. (c) Unenhanced CT scan obtained with a lung window setting at the level of the lower lobes shows marked stenosis of the left lower lobe arteries and dilatation of the accompanying bronchi (arrow); multiple linear opacities (arrowheads) adjacent to the pleural surface in the left lower lobe, suggestive of transpleural systemic vessels; marked dilatation of the vessels in the right lung; and a thrombus (*) in the right lower lobe artery.

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 25c.  Chronic pulmonary artery obstruction in a 68-year-old woman with dyspnea. (a) Contrast-enhanced CT scan at the level of the left hilum shows retracted embolic material (arrow); a marked reduction in the diameter of the left lower lobe pulmonary artery; and contrast material in the central lumen, a finding suggestive of recanalization of the artery. (b) Contrast-enhanced CT scan at a level slightly higher than a shows enlargement of the bronchial arteries (arrowhead) because of a bronchial system–to–pulmonary system shunt. (c) Unenhanced CT scan obtained with a lung window setting at the level of the lower lobes shows marked stenosis of the left lower lobe arteries and dilatation of the accompanying bronchi (arrow); multiple linear opacities (arrowheads) adjacent to the pleural surface in the left lower lobe, suggestive of transpleural systemic vessels; marked dilatation of the vessels in the right lung; and a thrombus (*) in the right lower lobe artery.

In patients with chronic pulmonary thromboembolism, dilatation of the segmental and/or sub-segmental bronchi may be observed in areas that are chronically devoid of pulmonary arterial perfusion (Fig 25c) (68).

Although most cases of chronic pulmonary thromboembolism involve multiple bilateral arterial abnormalities, occlusion of one main pulmonary artery, which mimics proximal interruption, has been reported in approximately 3% of cases (69).

Primary Sarcoma of Pulmonary Arteries
Undifferentiated sarcoma and leiomyosarcoma are the types of sarcoma that most frequently affect the pulmonary arteries (70). The main or proximal pulmonary arteries are most frequently involved. The clinical manifestations may mimic those in acute or chronic pulmonary embolism (71).

Contrast-enhanced CT scans show the tumor as an intraluminal filling defect that resembles a thromboembolus. The filling defect frequently spans the entire luminal diameter of the main or proximal pulmonary arteries (Fig 26), and this finding is unusual in pulmonary thromboembolism. Primary pulmonary artery sarcoma is strongly indicated if the mass expands the artery (71). Other findings that may be helpful for distinguishing a pulmonary artery sarcoma from a thromboembolus include extension into the mediastinum or lung and delayed enhancement at CT angiography (71).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 26.  Pulmonary artery sarcoma in a 70-year-old-man with dyspnea. Contrast-enhanced CT scan shows filling defects in the main, left, and right pulmonary arteries and the right interlobar pulmonary artery. The arterial lumina are expanded, and there is extravascular invasion.

	Conclusions

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

In the appropriate clinical setting (eg, infection or vasculitis), an awareness of the radiologic manifestations of possible pulmonary arterial complications may enable an early diagnosis.

Some of the entities reviewed, whether congenital in origin or acquired, result in decreased pulmonary flow and, thus, cause the development of systemic collateral vessels, mainly from the bronchial arteries.

	Acknowledgments

 
The authors thank Ricard Valero, MD, PhD, for illustrations and John Giba for linguistic aid.

	References

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Congenital Anomalies Increased Arterial Diameter Decreased Arterial Diameter Filling Defects Conclusions References

 

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