CASE 12209 Published on 14.12.2014

Pulmonary artery sling

Section

Paediatric radiology

Case Type

Clinical Cases

Authors

Inês Oliveira, Bruno Araújo, André Simões, Anabela Braga

Matosinhos, Portugal
Email:mariaioliveira@sapo.pt

Patient

2 months, male

Categories

Area of Interest Cardiovascular system, Paediatric ; Imaging Technique CT-Angiography, CT

Procedure Diagnostic procedure ; Special Focus Congenital ;

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Clinical History

A two-month-old male infant presented to the emergency department with a 24-hour history of fever and respiratory distress. Intermittent wheezing since birth was also reported.

Imaging Findings

A contrast-enhanced chest CT was performed, revealing a left pulmonary artery that arises from the proximal right pulmonary artery and courses to the left hilum, between the trachea and the oesophagus (Fig. 1, 2). There was also consolidation of the right lower lobe (Fig. 3).

Discussion

Failure of formation of the 6th aortic arch leads to absence of left pulmonary artery (LPA). The pulmonary artery sling (PAS) is an aberrant LPA that arises from right pulmonary artery (RPA) and crosses between the oesophagus and trachea [1].
The term “sling” is used when there is impingement on the right main bronchus by the proximal portion of the anomalous vessel, which may cause obstructive emphysema of the entire right lung, the right middle or lower lobe, depending on the site of compression [2, 3]. The other type of anomalous LPA origin, which is often fatal, is associated with long-segment tracheal stenosis due to cartilage rings [2-4].
In this case it is believed that the tracheal and right bronchial compression by the anomalous LPA caused wheezing, whereas the acute pulmonary distress was due to right lower lobe consolidation. There were no signs of tracheal rings or stenosis.
Imaging has an important role in the diagnostic workup of PAS. Plain films may show fetal fluid retention or air, with a mediastinal shift usually to the left side, barium oesophagram characteristically shows a mass between the trachea and the oesophagus, just above the level of the carina, echocardiography. Although pulmonary arteriography was historically regarded as essential for a definite diagnosis, cross-sectional echocardiography, computed tomography and magnetic resonance imaging depict the anomalous anatomy in detail. Enhanced CT generally demonstrates the anomalous vascular anatomy previously described and can obviate angiography. The bronchial tree can be delineated by virtual bronchoscopy. CT shows the abnormal origin of the LPA from the posterior aspect of the RPA and anomalous course between the lower portion of the trachea and the oesophagus. Impingement of the proximal portion of the right main bronchus can also be seen [5 - 7]. CT is usually the method of choice, as normal plain films do not exclude PAS, echocardiography is operator-dependent and MRI may not be available in the emergency setting.
Treatment of PAS is surgical, with reimplantation of the LPA into the main pulmonary artery and bronchoplasty [8, 9].
When isolated, PAS have a great prognosis [8]. Tracheal rings and long stenosis are associated with high mortality and morbidity rates during infancy [9].
PAS is a rare but otherwise well-known entity. There is one study that reported an incidence of 1:17.000 [10], but it should be included in the differential diagnosis of respiratory distress in newborns and infants, especially if associated with wheezing.

Differential Diagnosis List

Pulmonary artery sling

Infection

Aspiration

Final Diagnosis

Pulmonary artery sling

References

[1] Arey JB (1984) Malformations of the aorta and aortic arches. Cardiovascular pathology in infants and children. WB Saunders Company pp. 242–4

[2] Gross, Neuhauser E (2000) Rings, Slings, and Other Things: Vascular Compression of the Infant Trachea Updated from the Midcentury to the Millennium—The Legacy of Robert E. Radiology 216:624–632 (PMID: 10966687)

[3] Castañer E, et al (2006) Congenital and Acquired Pulmonary Artery Anomalies in the Adult: Radiologic Overview. RadioGraphics 26:349–371 (PMID: 16549603)

[4] Gikonyo BM, Jue KL, Edwards JE (1989) Pulmonary vascular sling: Report of seven cases and review of the literature. Pediatr Cardiol 10:81–9 (PMID: 2657677)

[5] Berlin S C et.al (1987) Pediatric case of the day. Pulmonary sling with tracheal stenosis and bronchus suis. AJR Am J Roentgenol 169(1):305, 308 (PMID: 9207560)

[6] Lee KH, et al (2001) Use of imaging for assessing anatomical relationships of tracheobronchial anomalies associated with left pulmonary artery sling. Pediatr Radiol Apr;31(4):269-78 (PMID: 11321746)

[7] Chen, Shyh-Jye et al (2007) Left Pulmonary Artery Sling Complex: Computed Tomography and Hypothesis of Embryogenesis. Ann Thorac Surg Nov;84(5):1645-50 (PMID: 17954077)

[8] P M Tan, T F Loh, N K Yong, K Sugai (1968) Aberrant left pulmonary artery. Br Heart J 30:110-114 (PMID: 5637543)

[9] Backer CL, Idriss FS, Holinger LD, Mavroudis C (1992) Pulmonary artery sling (results of surgical repair in infancy). J Thorac Cardiovasc Surg 103:683–91 (PMID: 1548911)

[10] Yu JM, Liao CP, Ge S, Weng ZC, Hsiung MC, Chang JK, Chen FL (2008) The prevalence and clinical impact of pulmonary artery sling on school-aged children: a large-scale screening study. Pediatr Pulmonol Jul;43(7):656-61 (PMID: 18484662)

Case information

URL:	https://www.eurorad.org/case/12209
DOI:	10.1594/EURORAD/CASE.12209
ISSN:	1563-4086

Figure 1

Pulmonary artery sling

Axial CT at the level of the pulmonary trunk shows the abnormal origin and course of the left pulmonary artery (arrowheads), between the lower portion of the trachea and the oesophagus (*).

Figure 2

Pulmonary artery sling

Coronal volumetric reconstruction shows the LPA (arrows) arising from the RPA (*), consistent with a pulmonary artery sling. The LPA is seen coursing from right to left between the trachea (T) and oesophagus (E).

Figure 3

Right lower lobe consolidation

Axial CT shows peripherally located consolidation with air bronchograms of the right lower lobe.

Figure 4

Pulmonary sling - Schematic drawing

Pulmonary sling. The aorta (red), oesophagus (brown) and pulmonary artery and branches (blue) are depicted, showing the abnormal origin of the LPA from the RPA.