DOI:10.2214/AJR.05.1652
AJR 2007; 188:W126-W134
© American Roentgen Ray Society
Pulmonary Artery Aneurysms and Pseudoaneurysms in Adults: Findings at CT and Radiography
Elsie T. Nguyen1,
C. Isabela S. Silva1,
Jean M. Seely2,
Semin Chong3,
Kyung Soo Lee3 and
Nestor L. Müller1
1 Department of Radiology, Vancouver General Hospital and The University of
British Columbia, 3350-950 W 10th Ave., Vancouver, BC V5Z 4E3, Canada.
2 Department of Radiology, The Ottawa Hospital, University of Ottawa, Ottawa, ON
K1Y 4E9, Canada.
3 Department of Radiology, Samsung Medical Center, Sungkyunkwan University
School of Medicine, Seoul 135-710, Korea.
Received September 16, 2005;
accepted after revision December 7, 2005.
Address correspondence to N. L. Müller.
WEB This is a Web exclusive article.
Abstract
OBJECTIVE. The purpose of this pictorial essay is to illustrate the
radiologic manifestations of pulmonary artery aneurysms and pseudoaneurysms
with emphasis on the findings on contrast-enhanced CT.
CONCLUSION. Pulmonary artery aneurysms and pseudoaneurysms are
uncommon. Most are caused by trauma, often iatrogenic, infection, and
Behçet's syndrome. Less common causes include pulmonary hypertension,
congenital heart disease, neoplasms, and connective tissue disease.
Recognition of pulmonary artery aneurysms and pseudoaneurysms is important
because of the high morbidity and mortality rates of rupture.
Keywords: aneurysms • CT angiography • CT arteriography • chest • CT • high-resolution CT • pseudoaneurysms
Introduction
Pulmonary artery aneurysms and pseudoaneurysms are uncommon but are
important to recognize because of the associated morbidity. By definition, an
aneurysm is focal dilatation of a blood vessel that involves all three layers
of vessel wall. A pseudoaneurysm does not involve all layers of the arterial
wall and is therefore at higher risk of rupture. The upper limit of normal
diameter of the main pulmonary artery on CT is 29 mm and of the right
interlobar artery is 17 mm [1].
We define aneurysm as focal dilatation of a pulmonary artery beyond its
maximal normal caliber.
Focal dilatation of the pulmonary arteries can be congenital or acquired.
Common causes include vasculitis, infection, neoplasm, and trauma, often
iatrogenic [1,
2]. On radiographs, aneurysms
may appear as hilar enlargement or a lung nodule. The diagnosis is usually
confirmed with contrast-enhanced CT. CT provides useful information regarding
the size, number, location, and extent of aneurysms and pseudoaneurysms
[3]. MRI also can show arterial
wall thickening in connective tissue disease and provide information regarding
blood flow direction in cases of poststenotic dilatation due to disease of the
pulmonary valve. Early recognition and treatment are important for reducing
morbidity and preventing mortality.
Congenital Causes
Congenital causes of pulmonary artery aneurysms and pseudoaneurysms include
deficiency of the vessel wall, valvular and postvalvular stenosis, and
increased flow due to left to right shunts. Increased hemodynamic shear
stresses (Fig. 1A,
1B,
1C) and increased flow due to
congenital heart disease (Fig.
2A,
2B) can result in giant
pulmonary artery aneurysms. Mural calcification can result from
atherosclerosis secondary to severe chronic pulmonary hypertension or from
calcified intramural thrombus. Common causes of left to right shunts resulting
in pulmonary artery volume and pressure overload leading to aneurysm formation
include patent ductus arteriosus (Fig.
3A,
3B,
3C,
3D), ventricular septal defect,
atrial septal defect, and sequelae of congenital heart disease repair,
including patch aneurysms in the tetralogy of Fallot. Risk of rupture or
dissection is highest in patients with severe pulmonary hypertension
associated with Eisenmenger's complex.
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Fig. 1A —47-year-old woman with congenital polycythemia vera, dyspnea, and
chest discomfort. (Courtesy of Dr. Kun Il Kim, Pusan, Korea) Posteroanterior
chest radiograph shows 9-cm round mass with peripheral calcification in left
upper hemithorax.
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Fig. 1B —47-year-old woman with congenital polycythemia vera, dyspnea, and
chest discomfort. (Courtesy of Dr. Kun Il Kim, Pusan, Korea) Contrast-enhanced
CT scan at 5-mm collimation shows marked enlargement of left pulmonary artery
corresponding to chest radiographic finding.
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Fig. 1C —47-year-old woman with congenital polycythemia vera, dyspnea, and
chest discomfort. (Courtesy of Dr. Kun Il Kim, Pusan, Korea) Contrast-enhanced
CT scan at 5-mm collimation shows markedly enlarged main and left pulmonary
arteries with extensive peripheral calcification. Mechanism of aneurysm
formation in this patient was unknown. It is likely that chronic pulmonary
arterial hypertension secondary to polycythemia contributed to formation of
large aneurysm.
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Fig. 2A —42-year-old woman with shortness of breath and left pulmonary artery
aneurysm due to aplasia of right pulmonary artery. Contrast-enhanced CT scan
shows aneurysm of main pulmonary artery and enlargement of left pulmonary
artery. Evident are prominent bronchial artery (curved arrow), right
internal mammary artery collateral vessels (straight arrow), and
aplasia of right pulmonary artery.
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Fig. 2B —42-year-old woman with shortness of breath and left pulmonary artery
aneurysm due to aplasia of right pulmonary artery. Contrast-enhanced CT scan
shows enlargement of left lower lobe segmental arteries and marked reduction
in size and number of right lower lobe pulmonary vessels. Also evident are
marked right atrial and right ventricular enlargement and right ventricular
hypertrophy with bowing of interventricular septum toward left ventricle,
indicating right-heart strain from pulmonary arterial hypertension.
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Fig. 3A —45-year-old man with patent ductus arteriosus. (Courtesy of Dr. Yeon
Hyeon Choe, Seoul, Korea) Posteroanterior chest radiograph shows curvilinear
calcification in region of left hilum (arrow), cardiomegaly, and
pulmonary vascular redistribution to upper lobes.
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Fig. 3B —45-year-old man with patent ductus arteriosus. (Courtesy of Dr. Yeon
Hyeon Choe, Seoul, Korea) Contrast-enhanced CT scan at level of aortopulmonary
window shows patent ductus arteriosus (arrow).
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Fig. 3C —45-year-old man with patent ductus arteriosus. (Courtesy of Dr. Yeon
Hyeon Choe, Seoul, Korea) Contrast-enhanced CT scan at level of main pulmonary
artery shows narrow base (arrow) of aneurysm of main pulmonary
artery.
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Fig. 3D —45-year-old man with patent ductus arteriosus. (Courtesy of Dr. Yeon
Hyeon Choe, Seoul, Korea) Coronal reconstruction shows patent ductus
arteriosus (white straight arrow) and pulmonary artery aneurysm
(curved arrow). Calcification is absent at communication (black
arrow) of aneurysmal sac and main pulmonary artery (MPA).
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Acquired Causes
Pulmonary Arterial Hypertension
Chronic pulmonary embolism is a relatively common cause of pulmonary artery
aneurysm formation (Fig. 4A,
4B,
4C). Such aneurysms tend to be
associated with mural thickening, webs, or intramural thrombi, which can
calcify. Other causes of pulmonary arterial hypertension can be classified
into precapillary (idiopathic, schistosomiasis), capillary (chronic
obstructive pulmonary disease, interstitial lung disease, fibrothorax), and
postcapillary (mitral valve stenosis, left heart failure, left atrial myxoma,
venoocclusive disease) causes. Idiopathic primary pulmonary hypertension is a
rare disease diagnosed when the underlying cause is unknown. It is
characterized by plexiform lesions, endothelial cell proliferation, and
concentric laminar intimal fibrosis of the pulmonary arteries
[4]. Plexogenic arteriopathy
also occurs in several connective tissue diseases, particularly progressive
systemic sclerosis, systemic lupus erythematosus, and mixed connective tissue
disease (Fig. 5A,
5B).
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Fig. 4A —57-year-old woman with pulmonary arterial hypertension due to
chronic pulmonary embolism. Cardiac catheterization yielded pulmonary artery
pressures of 66/26 mm Hg with mean pressure of 44 mm Hg. Unenhanced CT scan
shows enlargement of pulmonary arteries and calcified mural thrombus in left
pulmonary artery.
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Fig. 4B —57-year-old woman with pulmonary arterial hypertension due to
chronic pulmonary embolism. Cardiac catheterization yielded pulmonary artery
pressures of 66/26 mm Hg with mean pressure of 44 mm Hg. Contrast-enhanced CT
scan at same level as A shows enlarged bronchial arteries
(arrow).
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Fig. 4C —57-year-old woman with pulmonary arterial hypertension due to
chronic pulmonary embolism. Cardiac catheterization yielded pulmonary artery
pressures of 66/26 mm Hg with mean pressure of 44 mm Hg. High-resolution CT
image shows mosaic perfusion in upper lobes with enlargement of segmental
arteries in areas of increased attenuation.
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Fig. 5A —53-year-old woman with mixed connective tissue disease and shortness
of breath. Posteroanterior chest radiograph shows aneurysmal dilatation of
main (arrow), right, and left pulmonary arteries.
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Fig. 5B —53-year-old woman with mixed connective tissue disease and shortness
of breath. Lateral chest radiograph shows enlargement of central pulmonary
arteries and right ventricular outflow tract. Curvilinear calcification of
right pulmonary artery (arrow) is consistent with long-standing
pulmonary arterial hypertension. Patient had no evidence of interstitial lung
disease or pulmonary embolism. Echocardiography showed presence of pulmonary
arterial hypertension, which was clinically diagnosed as secondary to
plexogenic arteriopathy associated with mixed connective tissue disease.
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Vasculitis
The most common forms of vasculitis associated with pulmonary artery
aneurysms are Behçet's syndrome and Hughes-Stovin syndrome.
Behçet's syndrome is a chronic multisystem form of vasculitis
characterized by recurrent oral and genital ulcers and uveitis. It is seen
most commonly in Turkey and Southeast Asia. Behçet's syndrome commonly
results in pulmonary artery aneurysms
(Fig. 6), which typically
involve the right lower lobe arteries with frequent thrombosis and surrounding
inflammation [5,
6]. Although these pulmonary
artery aneurysms may regress with immunosuppressive medication, embolization
is often needed to prevent life-threatening hemoptysis.
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Fig. 7 —33-year-old man with hemoptysis and history of tuberculosis. Coronal
reconstruction of contrast-enhanced CT shows focal enhancement
(arrow) corresponding to Rasmussen aneurysm in posterior segment of
left upper lobe.
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Other thoracic manifestations of Behçet's syndrome include venous
thrombosis, pulmonary infarction and hemorrhage, recurrent pneumonia,
organizing pneumonia, eosinophilic pneumonia, and pleural effusion
[6].
Hughes-Stovin syndrome is characterized by recurrent thrombophlebitis and
pulmonary artery aneurysm formation and rupture. Some investigators
[7] have suggested that
Behçet's syndrome and Hughes-Stovin syndrome are part of the same
disease process.
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Fig. 8A —62-year-old woman with fever and cough due to community-acquired
pneumonia. Unenhanced CT scan shows focus of increased attenuation within
right middle lobe consolidation corresponding to thrombus or hemorrhage within
mycotic segmental artery pseudoaneurysm (arrow).
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Fig. 8B —62-year-old woman with fever and cough due to community-acquired
pneumonia. Contrast-enhanced CT scan at same level as A shows focus of
enhancement corresponding to pseudoaneurysm (arrow).
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Fig. 9A —70-year-old woman with angiosarcoma metastatic to lungs.
Contrast-enhanced axial (A) and coronal oblique (B) CT scans
show multiple pulmonary metastatic lesions and right lower lobe segmental
pulmonary artery pseudoaneurysm.
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Fig. 9B —70-year-old woman with angiosarcoma metastatic to lungs.
Contrast-enhanced axial (A) and coronal oblique (B) CT scans
show multiple pulmonary metastatic lesions and right lower lobe segmental
pulmonary artery pseudoaneurysm.
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Fig. 10B —57-year-old woman with pseudoaneurysm induced by Swan-Ganz catheter.
Sagittal oblique maximum-intensity-projection images at mediastinal (B)
and lung (C) windows show origin of pseudoaneurysm
(arrows).
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Fig. 10C —57-year-old woman with pseudoaneurysm induced by Swan-Ganz catheter.
Sagittal oblique maximum-intensity-projection images at mediastinal (B)
and lung (C) windows show origin of pseudoaneurysm
(arrows).
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Mycotic Aneurysms and Pseudoaneurysms
Infection with tuberculosis, pyogenic bacteria, and fungi can cause
pseudoaneurysm or, less commonly, aneurysm formation and is associated with
the risk of pulmonary hemorrhage and life-threatening hemoptysis. Pulmonary
artery pseudoaneurysms secondary to pulmonary tuberculosis are known as
Rasmussen aneurysms and usually involve the upper lobes in the setting of
reactivation tuberculosis (Fig.
7). The diagnosis can be readily made on the basis of the
characteristic findings of focal pulmonary artery dilatation associated with
postprimary tuberculosis.
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Fig. 11A —63-year-old man after insertion of right-chest tube for drainage of
empyema. (Courtesy of Dr. Young Tong Kim, Chunan, Korea) Contrast-enhanced CT
scan shows two adjacent pseudoaneurysms (arrows) in right middle lobe
caused by tube thoracostomy.
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Fig. 11B —63-year-old man after insertion of right-chest tube for drainage of
empyema. (Courtesy of Dr. Young Tong Kim, Chunan, Korea) Three-dimensional
shaded surface display shows origin of two pseudoaneurysms and their relation
to each other.
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Fig. 12A —56-year-old woman with hemoptysis after conventional angiography.
(Courtesy of Dr. Catherine Staples, Kelowna, BC, Canada) Contrast-enhanced CT
scan shows pseudoaneurysm in right middle lobe surrounded by pulmonary
hemorrhage.
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Fig. 12B —56-year-old woman with hemoptysis after conventional angiography.
(Courtesy of Dr. Catherine Staples, Kelowna, BC, Canada) Maximum intensity
projection with lung windows at same level as A shows area of
consolidation in right middle lobe corresponding to pulmonary hemorrhage. Less
extensive peripheral consolidation with centrilobular nodularity is evident in
right lower lobe because of presence of aspirated blood.
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Pyogenic bacteria are an increasingly common cause of pulmonary artery
pseudoaneurysm formation. Mycotic pulmonary aneurysms and pseudoaneurysms
caused by bacteria are seen mainly in IV drug users and are usually associated
with infective endocarditis and septic embolism
[1]. Other causes of mycotic
aneurysms include bacterial (Fig.
8A,
8B) and fungal pneumonia and
cardiothoracic surgery.
Neoplasm
Primary lung cancer and pulmonary metastasis (Fig.
9A,
9B) can cause erosion into the
pulmonary arteries and result in pseudoaneurysm formation. In rare instances,
primary tumors arising from the pulmonary arteries, such as leiomyosarcoma and
angiosarcoma, can cause focal expansion and aneurysmal dilatation.
Iatrogenic Causes
Malpositioned Swan-Ganz catheters are an increasingly common cause of
iatrogenic pulmonary artery pseudoaneurysm. In one prospective study
[8] with 500 consecutively
enrolled patients, the incidence of rupture and hemorrhage after Swan-Ganz
catheter insertion was 0.2%. The complication occurs mainly in patients in
whom the Swan-Ganz catheter has been inserted too far into a pulmonary
arterial branch. The tip of the catheter begins to erode the wall of the
artery and causes weakening and dilatation. The vessel ruptures where
extravasated blood is contained by adventitia, or thrombus forms a
pseudoaneurysm (Fig. 10A,
10B,
10C,
10D).
Other iatrogenic causes include chest tube insertion (Fig.
11A,
11B), conventional angiography
(Fig. 12A,
12B), and surgical resection
or biopsy. Penetrating trauma (i.e., stab and gunshot wounds) can cause
pulmonary artery pseudoaneurysms. The history is important in making the
diagnosis, and coil embolization is the first-line treatment.
Connective Tissue Abnormalities
Intrinsic weakness in the arterial wall due to connective tissue
abnormalities such as Marfan syndrome, Ehlers-Danlos syndrome, and cystic
medial necrosis also predispose to aneurysm formation. Aneurysms in these
patients typically involve the aorta but also can affect the pulmonary
arteries.
Conclusion
Although pulmonary artery aneurysms and pseudoaneurysms are uncommon,
knowledge of their congenital and acquired causes and radiologic
manifestations is important. Assessment with contrast-enhanced CT allows
accurate evaluation of pulmonary artery aneurysms and pseudoaneurysms,
facilitating prompt diagnosis and treatment.
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Abstract
Introduction
