Sling left pulmonary artery with patent type IIA tracheobronchial anomaly and imperforate anus
Transcript of Sling left pulmonary artery with patent type IIA tracheobronchial anomaly and imperforate anus
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Sling left pulmonary artery with patent type IIA tracheobronchial anomalyand imperforate anus
Daniel G. Rosenbaum, Ericalyn Kasdorf, Pooja Renjen, Paula Brill,Arzu Kovanlikaya
PII: S0899-7071(14)00113-2DOI: doi: 10.1016/j.clinimag.2014.04.012Reference: JCT 7614
To appear in: Journal of Clinical Imaging
Received date: 25 March 2014Revised date: 15 April 2014Accepted date: 23 April 2014
Please cite this article as: Rosenbaum Daniel G., Kasdorf Ericalyn, Renjen Pooja,Brill Paula, Kovanlikaya Arzu, Sling left pulmonary artery with patent type IIA tra-cheobronchial anomaly and imperforate anus, Journal of Clinical Imaging (2014), doi:10.1016/j.clinimag.2014.04.012
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Sling left pulmonary artery with patent type IIA tracheobronchial anomaly and imperforate anus
Abbreviated title: SLPA with type IIA anomaly
Daniel G. Rosenbaum, MD
Department of Radiology, NewYork-Presbyterian Hospital/Weill Cornell, Medical
Center, 525 E. 68th
St., New York, NY, 10065
Ericalyn Kasdorf, MD
Department of Pediatrics, NewYork-Presbyterian Hospital/Weill Cornell, Medical
Center, 525 E. 68th
St., New York, NY, 10065
Pooja Renjen, MD
Department of Radiology, NewYork-Presbyterian Hospital/Weill Cornell, Medical
Center, 525 E. 68th
St., New York, NY, 10065
Paula Brill, MD
Department of Radiology, NewYork-Presbyterian Hospital/Weill Cornell, Medical
Center, 525 E. 68th
St., New York, NY, 10065
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Arzu Kovanlikaya, MD (Corresponding author)
Department of Radiology, New York-Presbyterian Hospital, 525 E. 68th
St., New
York, NY, 10065
Phone: 212-746-2555
Fax: 212-746-8229
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Abstract
We present a 3-month-old boy with a type IIA sling left pulmonary artery associated with
imperforate anus and rectourethral fistula. Tracheobronchial abnormalities are demonstrated
using multidetector CT with 3-D volume rendering of the airways. This case represents a novel
variant of an already rare entity with an unusually high right upper lobe bronchus and no
evidence of associated tracheobronchial stenosis.
Index Terms
Thoracic imaging
Congenital abnormalities
Neonatal airway anatomy
Multidetector computed tomography
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Introduction
Sling left pulmonary artery (SLPA) is a relatively rare vascular abnormality, and may be
associated with aberrant branching patterns of the tracheobronchial tree, the latter of which
usually determines prognosis and management. Certain subtypes may also be associated with
extra-thoracic abnormalities such as imperforate anus (1). The pulmonary vascular and
tracheobronchial abnormalities generally present early in life with respiratory compromise,
however they may occasionally be occult lesions. While a classification scheme for such
abnormalities was first described by Wells and Landing in 1988, the advancement of imaging
capabilities and post-processing techniques, particularly multidetector CT (MDCT), has led to
refinement of this classification over the past few decades, with increased emphasis upon overall
airway configuration rather than the level of specific airway branch points (1,2). We report a
case that, to our knowledge, is unique in its high right upper lobe bronchus, but nonetheless falls
into the type IIA category, with a classic bridging bronchus. The lesion was only minimally
symptomatic, and was detected as a result of a workup for VACTERL association.
Case report
A male infant with an unremarkable prenatal history was delivered via C-section at 33
weeks’ gestation due to decreased fetal heart rate. He was found to have a single umbilical artery
and an imperforate anus. Chest radiograph performed for prematurity demonstrated granular
opacities, reported as likely reflecting mild surfactant deficiency disorder. The patient had
normal oxygenation and was not tachypneic, but did demonstrate occasional mild noisy
breathing. Laryngoscopy was normal. He underwent transverse loop colostomy on day 0 of life
as well as cystoscopy, which revealed multiple false passages in the urethra at the level of the
external sphincter. As part of a subsequent workup for VACTERL association, he had an
echocardiogram, which showed a left pulmonary artery sling with possible tracheal compromise.
Contrast-enhanced MDCT was performed for further anatomic delineation on a Discovery
CT750 HD scanner (General Electric, Milwaukee, WI, USA) with the following acquisition
parameters: 80 kVp, 200 mA, and pitch 1.375 (recorded CTDIvol 3.81 mGy). MDCT showed a
sling left pulmonary artery originating from the right pulmonary artery. There was a high right
upper lobe bronchus arising at the level of T2. The left intermediate bronchus continued
inferiorly within the mediastinum to the level of T6-T7, at which point it trifurcated into the left
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upper and lower lobe bronchi, and a bridging bronchus supplying the right lower lobe; the right
middle lobe was absent (Fig. 1). 3-D volume rendering was performed from minimal intensity
projections in order to confirm and better delineate the tracheobronchial abnormality (Fig. 2).
Subsequent distal colostogram demonstrated a rectourethral fistula, with voiding
cystourethrogram further defining a fistulous tract from the proximal bulbar urethra (Fig. 3), as
well as bilateral grade III vesicoureteral reflux. The patient is currently awaiting posterior sagittal
anorectoplasty, and has not undergone bronchoscopy due to absence of significant respiratory
symptoms or evidence of tracheobronchial stenosis on imaging.
Discussion
Tracheobronchial tree abnormalities are rare in the general population, occurring in
approximately 0.1-1.9% of children, but are commonly associated with SLPA (3). A
classification scheme for this association was introduced by Wells and Landing in 1988 based
upon pathologic specimens and bronchography. This scheme divided the abnormalities into two
types based on a normal tracheal bifurcation at T4-T5 (type I) or a low bifurcation at T5-T7 (type
II), and two subtypes according to the presence (subtype A) or absence (subtype B) of a right
upper lobe eparterial bronchus (1). Type II lesions are also characterized by a bridging bronchus,
a term first introduced to describe an airway malformation in which the right upper lobe is
supplied by the right main bronchus while the right middle and lower lobes are supplied by a
bronchus that originates from the left main bronchus, coursing within the mediastinum from left
to right (4). More recently, the classification scheme has been adapted to MDCT by Zhong et al.
in 2010, who observed more variability in the level of the tracheal bifurcation than previously
reported, and chose to base their classification primarily on the configuration of the
tracheobronchial tree (2). Our case further highlights the variability of these anomalies,
representing an atypical example of SLPA type IIA in several respects. Our patient demonstrated
a high right upper lobe bronchus at the level of T2 and a long left intermediate bronchus giving
rise to a bridging bronchus at T6-T7, a configuration different from that described by Wells, in
which the right main bronchus takeoff occurs at the expected level of T4-T5 (Fig. 4). The airway
patency on imaging and minimal symptoms are also unusual for a type IIA anomaly, and differ
from multiple prior case series in which all patients with type IIA lesions have had long segment
tracheobronchial stenosis (generally related to complete cartilage rings and absence of the pars
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membranacea) and most have presented with shortness of breath or stridor (2, 5). These features
reinforce the notion that the airway anomaly rather than the vascular anomaly dictates prognosis
and management in SLPA.
Terminology regarding the bronchial branching pattern in type II abnormalities has been
controversial. Because the airway segment between the tracheal bifurcation and the bridging
bronchus remains mediastinal well below the level of the normal carina, this segment has been
termed the “left intermediate bronchus” (6). The proximal airway bifurcation to the right has not
been designated a tracheal bronchus in prior reports in part because it arose at, rather than above,
the normal level of the carina. While the current case poses a nomenclatural challenge, we
believe that the high right upper lobe bronchus could reasonably be termed a right main bronchus
or a displaced tracheal bronchus without changing the lesion’s overall categorization as a type
IIA anomaly.
SLPA has been observed in conjunction with multiple cardiac and non-cardiac
abnormalities, including esophageal atresia, biliary atresia, Hirschprung’s disease, and dysplastic
sacrum (1,3,5). The particular association between SLPA and imperforate anus was noted in the
initial case series and literature review of Wells et al., in which 14% of patients with type II
anomalies and 40% of those with type IIA anomalies had an imperforate anus (1). Since that
time, few additional cases of this association have been reported, but notably include a type IIA
lesion in which the bridging bronchus and main bronchi were normal in caliber (7), as was the
case in our patient.
MDCT with 3-D volume rendering of the airways is extremely helpful in the
characterization of tracheobronchial anomalies associated with SLPA. Prior investigations of
comparative diagnostic ability have found that while bronchoscopy is useful in the detection of
complete cartilage rings, distinguishing between the proximal airway bifurcation and the more
distal takeoff of the bridging bronchus may be difficult, and high-grade stenosis may preclude
complete evaluation (3). MDCT has been shown to delineate the full spectrum of abnormalities
quite well with reasonably low radiation doses, informing a refined classification scheme, and
has been used more recently to generate 3-D volume rendered images that clearly define
anatomy and guide surgical planning where appropriate (2,3,5,8). Magnetic resonance imaging
has also been successful in distinguishing between type I and type II lesions (6), but involves
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longer acquisition times, may require sedation, and even minor motion artifact may complicate
interpretation of airway patency in very young patients.
In conclusion, our case highlights the variability of abnormalities and clinical
presentations found in SLPA with respect to both the tracheobronchial tree and extra-thoracic
organ systems, and reinforces the role of MDCT in the accurate delineation of difficult anatomy.
Clinicians and radiologists should be aware of the spectrum of these abnormalities and their
associations in order to facilitate timely diagnosis and establish a comprehensive treatment plan.
References
1. Wells TR, Gwinn JL, Landing BH, Stanley P. Reconsideration of the anatomy of the
sling left pulmonary artery: the association of one form with bridging bronchus and
imperforate anus. Anatomic and diagnostic aspects. J Pediatr Surg 1988;23:892–898.
2. Zhong YM, Jaffe RB, Zhu M, Gao W, Sun AM, Wang Q. CT assessment of
tracheobronchial anomaly in left pulmonary artery sling. Pediatr Radiol 2010;40:1755-
1762.
3. Baden W, Schaefer J, Kumpf M, Tzaribachev N, Pantalitschka T, Koitschev A, Ziemer
G, Fuchs J, Hofbeck M. Comparison of imaging techniques in the diagnosis of bridging
bronchus. Eur Respir J 2008;31:1125-1131.
4. Gonzalez-Crussi F, Padilla LM, Miller JK, Grosfeld JL. Bridging bronchus. A previously
undescribed airway anomaly. Am J Dis Child 1976;130:1015–1018.
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assessing anatomical relationships of tracheobronchial anomalies associated with left
pulmonary artery sling. Pediatr Radiol 2001;31:269-278.
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delineation of associated tracheobronchial anomalies with MR. Pediatr Radiol
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Fig. 1: Axial MDCT images of type IIA sling left pulmonary artery demonstrate a high right
upper lobe bronchus at the level of T2 (arrow in a), a widely patent left intermediate bronchus
(arrow in b) coursing within the mediastinum anterior to the sling left pulmonary artery
(arrowhead in b), and a distal trifurcation at T6-T7 giving rise to the left upper lobe bronchus
(white arrow in c), left lower lobe bronchus (black arrow in c), and a bridging bronchus coursing
toward the right lower lobe (arrowhead in c).
Fig. 2: a) AP volume rendering of the airways more clearly demonstrates the high right upper
lobe bronchus, patent left intermediate bronchus (arrow), and distal trifurcation with bridging
bronchus (arrowhead). b) PA volume rendering including vasculature shows the relationship of
the airway anomaly to the great vessels, with the left pulmonary artery (asterisk) coursing
posterior to the distal trifurcation (dashed line).
Fig. 3: Voiding cytourethrogram following distal colostogram at the level of the distal rectum
shows a fistulous connection to the bulbar urethra (arrow).
Fig. 4: Classification of type II tracheobronchial abnormalities in LPAS (modified from Wells et
al. and Zhong et al.). Black circle represents the left pulmonary artery. Type IIA abnormalities
demonstrate a pseudocarina giving rise to a bridging bronchus (BB), often with a stenotic left
intermediate bronchus (LIB); type IIB lesions also have a bridging bronchus, but have an absent
or atretic right upper lobe bronchus. The study case falls within the type IIA category, but is
unusual in its high right upper lobe bronchus and widely patent left intermediate bronchus.
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Fig. 1A
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Fig. 1B
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Fig. 1C
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Fig. 2A
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Fig. B
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Fig. 3
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Fig. 4