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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

ark2011@med.cornell.edu

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.

5. Lee KH, Yoon CS, Choe KO, Kim MJ, Lee HM, Yoon KH, Kim B. Use of imaging for

assessing anatomical relationships of tracheobronchial anomalies associated with left

pulmonary artery sling. Pediatr Radiol 2001;31:269-278.

6. Newman B, Mesa MP, Towbin RB, Nido PD. Left pulmonary artery sling: diagnosis and

delineation of associated tracheobronchial anomalies with MR. Pediatr Radiol

1996;26:661–668.

7. Medina-Escobedo G, Lopez-Corella E.Sling left pulmonary artery, bridging bronchus,

and associated anomalies. Am J Med Genet 1992; 44:303-306.

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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