AJR 2005; 184:1241-1244
© American Roentgen Ray Society
Aneurysm of an Aberrant Systemic Artery to the Lung
Servet Tatli1,
E. Kent Yucel1,
Gregory S. Couper2,
Joel M. Henderson3 and
Yolonda L. Colson4
1 Department of Radiology, Brigham and Women's Hospital, Harvard Medical School,
75 Francis St., Boston, MA 02115.
2 Division of Cardiac Surgery, Department of Surgery, Brigham and Women's
Hospital, Harvard Medical School, Boston, MA.
3 Department of Pathology, Brigham and Women's Hospital, Harvard Medical School,
Boston, MA.
4 Division of Thoracic Surgery, Department of Surgery, Brigham and Women's
Hospital, Harvard Medical School, Boston, MA.
Received April 21, 2004;
accepted after revision July 14, 2004.
Address correspondence to S. Tatli
(statli{at}partners.org).
Introduction
Systemic arterial supply to pulmonary parenchyma is a rare
congenital anomaly [1].
Pulmonary sequestration is one of the most common congenital pulmonary
malformations in which the involved lung parenchyma is supplied by an aberrant
systemic artery
[1-5].
Rarely, an anomalous systemic artery may supply an area of otherwise normal
lung, which is generally the posterobasal segment of the left lower lobe
[5-8].
An aneurysm of the aberrant artery to lung is extremely rare with only three
previously reported cases in the literature
[9-11].
We report a case of a fusiform aneurysm of an aberrant systemic artery to
the lung that arose from the distal descending thoracic aorta, supplying the
posterobasal segment of the right lung, with maximal diameter of 3 cm. The
diagnosis was accurately made using CT angiography using a multidetector
scanner. The patient was treated successfully by right lower lobectomy and
resection of the aneurysmal aberrant artery.
Case Report
A 47-year-old woman was referred to our hospital for evaluation of a right
paraspinal mass incidentally seen on thoracic spine MRI performed for back
pain. CT angiography of the aorta was performed on a 16-MDCT scanner (Somatom
Sensation 16, Siemens) from the aortic arch to the iliac crest before and
after IV administration of 100 mL of contrast material (Ultravist 300
[iopromide], Schering) at 3 mL/sec (collimation, 0.75 mm; slice thickness,
0.75 mm; reconstruction interval, 0.5 mm). The obtained images were
reconstructed in axial, coronal, and sagittal planes with 3-mm slice thickness
and 1.5-mm reconstruction interval. Three-dimensional reconstructions using a
volume-rendering technique were also obtained on a separate workstation.
The images showed that the paraspinal mass was an aneurysm of an anomalous
artery arising from the aorta at the level of the aortic hiatus (Figs.
1A,
1B,
1C,
1D,
1E, and
1F). The anomalous artery was 4
mm in diameter, arising from the left ventral side of the aorta above the
celiac axis (Fig. 1A), crossing
the midline anterior to the aorta, and entering into the lung parenchyma of
the posterior basal segment of the right lower lobe. A fusiform aneurysmal
dilatation developed within the 6.5-cm-long segment of the anomalous artery
situated within the parenchyma of the right lower lobe (Figs.
1B and
1C). The maximal diameter of
the aneurysm was 3 cm. The aneurysm had thick eccentric mural thrombosis with
partial calcification (Fig.
1B). After the aneurysmal segment, the anomalous artery extended
superiorly and gave rise to several branches into the parenchyma of the right
lower lobe (Fig. 1C). There was
no obvious communication with pulmonary veins, and abnormal pulmonary or
systemic venous channels were not noted.
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Fig. 1A. —47-year-old woman who presented with right paraspinal mass.
Contrast-enhanced axial CT image (collimation, 0.75 mm; slice thickness, 3 mm;
reconstruction interval, 1.5 mm) obtained through aortic hiatus shows aberrant
artery (white arrowheads) arising from aorta anteriorly (A). Fusiform
partially enhancing right paraspinal mass (black arrowheads) is
aneurysm of aberrant artery. Note aneurysm is partially thrombosed
(star).
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Fig. 1B. —47-year-old woman who presented with right paraspinal mass.
Coronal reformation of CT angiogram (slice thickness, 3 mm; reconstruction
interval, 1.5 mm) obtained at lower thoracic level shows partially thrombosed
aneurysm (arrowhead) in right lung base.
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Fig. 1C. —47-year-old woman who presented with right paraspinal mass.
Three-dimensional reformation of CT angiogram with volume-rendering technique
was obtained on separate workstation. Note excellent visualization of aneurysm
(A) of aberrant artery (arrowhead) arising from aorta. Heart,
bifurcation of main pulmonary artery (MPA), and origin of celiac axis
(arrow) are shown.
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Fig. 1D. —47-year-old woman who presented with right paraspinal mass.
Axial CT image obtained at level of trifurcation of lower lobe bronchus shows
bronchus of right posterobasal segment (short arrow) has no
accompanying interlobar artery. Note bronchus of left posterobasal segment
(arrowhead) with accompanying artery (long arrow).
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Fig. 1E. —47-year-old woman who presented with right paraspinal mass.
Axial CT image obtained with lung window settings through lower lungs shows
lung parenchyma that is supplied by aberrant artery (arrowhead) is
normal.
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The main and right pulmonary arteries were normal in appearance with the
exception that the posterobasal branch of the lower lobe pulmonary artery was
absent (Fig. 1D). The lung
parenchyma adjacent to the aneurysmal anomalous artery was grossly normal in
appearance with no consolidation, fluid collection, or cystic lesion
(Fig. 1E). The rest of the lung
parenchyma and the vascular system were otherwise normal. Diagnosis of an
aneurysm of the anomalous artery to the lung was established.
The patient was scheduled for elective right lower lobectomy to prevent
expansion of the aneurysm with potential rupture. Intra-operative
bronchoscopic and esophagogastroduodenoscopic evaluations were performed to
rule out any anomalies that can be associated with pulmonary sequestrations
and that might be missed by radiographic imaging. These studies revealed no
obvious abnormalities. The aneurysm and right lung were accessed via a right
lateral thoracotomy. On examination, the aneurysm was pulsatile, passed within
the sheaths of the inferior pulmonary ligament, and extended well into the
parenchyma of the lower lobe. The associated parenchyma was thickened, and
there were no other lesions within the remainder of the lung.
A lower lobectomy was undertaken with ligation of the inferior pulmonary
vein before manipulation of the lung parenchyma and subsequent resection of
the aneurysmal aberrant artery. The entire specimen was sent for
histopathologic evaluation, which confirmed an intralobar sequestration with
aneurysm of the aberrant artery (Fig.
1F). The posterior basal segment bronchus communicated normally
with the right lower lobe bronchus, and the lung parenchyma was normal. On
histology, there was a substantial amount of elastic tissue throughout the
wall of the aberrant artery, similar to that of pulmonary artery.
Discussion
Systemic arterial supply to the lungs can occur in association with
congenital heart and lung diseases
[1,
2]. Hypertrophy of normal
regional systemic arteries (i.e., bronchial, intercostal, inferior phrenic
arteries, or branches of the abdominal aorta) may also be acquired in patients
with chronic pulmonary inflammatory diseases such as bronchiectasis
[2]. Pulmonary sequestration is
one of the most common congenital pulmonary malformations in which the
involved lung parenchyma is supplied by an aberrant systemic artery
[3,
4]. Rarely, an anomalous
systemic artery may supply an area of otherwise normal lung in the absence of
congenital or acquired heart and lung disease. This latter condition has been
traditionally considered within the broad framework of pulmonary sequestration
as a mild form of intralobar pulmonary sequestration. This subset was first
classified in 1946 as Pryce type 1 intralobar sequestration
[5]. Other authors have
classified these rare lesions as a distinct entity because true sequestration
requires that the lung parenchyma supplied by the aberrant systemic artery be
abnormal and disconnected from the normal tracheobronchial airway
[6,
7].
A systemic arterial supply to otherwise normal lung, as was present in this
patient, is extremely rare; it has been reported in approximately 30 cases in
the Japanese-language literature
[8]. Most pediatric patients
present with a cardiac murmur. Because this anomaly is hemodynamically a
left-to-right shunt, patients may develop high-output heart failure. Most
adult patients are asymptomatic or have recurrent hemoptysis, which is
believed to be caused by secondary pulmonary hypertension of the involved lung
and is attributed to long-term exposure of the parenchyma to systemic arterial
pressure [6]. The basal
segments of the left lower lobe are most frequently involved
[6,
7] with right lower lobe
involvement, as in our case, being rare. The pulmonary parenchyma and
bronchial tree are often normal, but pulmonary congestion with or without
evidence of hemorrhage in the alveoli may be seen
[7]. Pathologically, no direct
communication exists between the anomalous systemic artery and the veins of
the basal segments. Venous return is via the large inferior pulmonary vein
into the left atrium.
In our patient, the anomalous artery was supplying an otherwise normal
posteromedial segment of the lung. The tracheobronchial communication, lung
parenchyma, and venous system were normal consistent with a intralobar
pulmonary sequestration, Pryce type 1. In addition, the anomalous artery was
aneurysmal along a 6-cm-long segment, thus simulating a paraspinal mass on
chest radiography and spine MRI. It is believed that such aneurysms carry a
high risk of rupture and should be treated surgically.
Systemic arterial supply to the lung is derived embryologically as a
persistent primitive aortic branch that originally supplied the developing
lung bud [1,
6]. The vascular plexus of the
primary lung buds is derived from the segmental arteries that arise from the
dorsal aorta. Normally, these aortic connections disappear as the main
pulmonary artery develops. If this transition fails, persistent systemic
arterial communication continues to be the major blood supply to an otherwise
normal lung [6]. The anomalous
artery most commonly arises from the descending thoracic aorta and less often
from the abdominal aorta or one of its branches; it commonly enters the lung
parenchyma by way of the lower part of the pulmonary ligament. The artery is
frequently tortuous, thick-walled, and larger than would be expected for the
volume of tissue supplied. Histologically, the anomalous artery generally has
an elastic wall that resembles the wall of a pulmonary artery rather than that
of a bronchial artery, and atheromatous changes are common, as was seen in our
patient.
Although these aberrant arteries can be large, aneurysmal dilation of these
arteries is extremely rare with only three cases having been reported in the
literature
[9-11].
Janssen et al. [9] previously
reported a case of a right lower lobe bronchopulmonary sequestration
associated with an aneurysm of the aberrant artery that initially presented as
pneumonia. Sudo et al. [10]
reported a case of an aneurysmal aberrant artery arising from the descending
aorta and supplying the left basal segment in a 65-year-old man who presented
with fever. In a case report by Koyama et al.
[11], a 47-year-old woman, who
presented with hemoptysis and opacity in the lung on chest radiography,
underwent left lobe resection, which revealed an aneurysm of aberrant artery
filled with thrombus.
Radiographically, the anomalous artery appears as an ill-defined nodular
area of increased opacity in the medial aspect of the lower lobe on a
posteroanterior chest radiograph. Visualization of the origin and course of
the anomalous artery has improved considerably with the advent of helical CT
that allows overlapping slice reconstruction, multiplanar display, and 3D
reconstructions [3]. The
anomalous artery is seen as an enhancing linear or tubular structure coursing
from the lower thoracic or upper abdominal aorta through the inferior
pulmonary ligament into the involved lung. CT shows not only systemic vessels
but also characteristic parenchymal lesions and associated findings.
In our patient, the aneurysm of the aberrant artery was correctly diagnosed
on CT angiography. Multiplanar reformations and 3D reconstructions improved
the visualization of the anomalous artery to allow surgical planning without
the need for invasive angiography.
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Introduction
Case Report
