Pediatric Chest: A Review of the Must-know Diagnoses

Shreya Sood, MD; Julia Rissmiller, MD; Anastasia Hryhorczuk, MD

Disclosures

Appl Radiol. 2018;47(4):4-14. 

In This Article

Vascular Rings

Vascular rings arise from the persistence of embryonic aortic arches.

Double Aortic Arch

Double aortic arches account for roughly 50% of symptomatic vascular rings.[16] These vascular abnormalities occur when both the right and left fourth embryonic aortic arches persist, encircling both the trachea and esophagus. While both arches may be patent, a segment of one arch may also be hypoplastic or atretric. Most patients demonstrate dominant right aortic arches, which are larger and rostral to the left arch (Figure 4).

Figure 4.

1 month-19-day-old infant male with feeding difficulty. (A) Lateral projection from barium swallow demonstrates posterior indentation on the esophagus (arrow). (B) MRI/MRA of the chest. Axial MRA shows the classic "four vessel sign" of double aortic arch. The right aortic arch is dominant (arrow) and is seen more rostral in positioning than the left arch. Findings are compatible with a double aortic arch.

Characteristically, tracheal compression from the vascular ring produces inspiratory stridor that worsens during food ingestion. Associated tracheomalacia may worsen these symptoms. On fluoroscopic barium swallow studies, bilateral indentations may be visible on the upper esophagus, with additional compression along the posterior esophageal wall. Cross-sectional imaging findings include the "four vessel sign," created when each arch gives rise to its ipsilateral subclavian and common carotid arteries. Treatment involves surgical ligation of the smaller arch.

Right Aortic Arch

A right aortic arch reflects persistence of the right fourth embryonic arch. A right arch will cross over the right mainstem bronchus. The location of the descending aorta is variable; along either the right or left posterior mediastinum (Figure 5). Two main subtypes of right aortic arch are: a right aortic arch with aberrant left subclavian artery (RLSCA) or a right arch with mirror-branch type pattern. The RLSCA subtype is asymptomatic in up to 95% of cases. A complete ring is only formed if a left ligamentum arteriosum is present, which may cause respiratory symptoms.[16] The aberrant left subclavian artery may have aneurysmal dilatation at its origin, arising from a remnant of the left dorsal aortic root. This is termed the "diverticulum of Kommerell". If vascular rings are symptomatic, they are treated by transection of the ligamentum arteriosum.

Figure 5.

16-year-old female with cough. (A) Coned-down view of the trachea on frontal chest x-ray demonstrates a leftward deviation of the trachea (arrow). Two axial (B, C) and a coronal (D) CECT scans in soft tissue mediastinal windows at the level of aortic arch demonstrate right aortic arch (arrowhead) that during its courses into becoming the descending aorta lies posterior to the trachea (curved arrow). On coronal (D) view, there is leftward deviation of the trachea at the level of the arch (arrow), as seen on chest x-ray, due to the right-sided arch. CT also demonstrated an aberrant left subclavian artery (not shown). Findings are compatible with a right aortic arch with aberrant left subclavian artery.

The right aortic arch with mirror branching is the second-most common right aortic arch branching pattern and reflects a mirror image of the left aortic arch.[17] Without a true vascular ring, this branching pattern is largely asymptomatic. However, it is notable for a high association with congenital heart disease, including Tetralogy of Fallot and truncus arteriosus. The first branch of the mirror arch is the left brachiocephalic artery, followed by the right common carotid artery and the right subclavian artery.

Left Aortic Arch With Aberrant Right Subclavian Artery

The left aortic arch with aberrant right subclavian artery (LRSCA) is the most common congenital aortic arch anomaly, occurring in roughly 1 of every 200 people.[17] Since this vascular branching pattern is not associated with respiratory compromise, it is typically identified incidentally. When symptomatic, it is usually due to mass effect on the posterior esophagus causing "dysphagia lusoria" or difficulty swallowing. Chest x-rays may be normal or demonstrate subtle mediastinal widening. If a barium swallow is performed, an oblique region of mass effect may be seen along the course of the aberrant vessel as it compresses the posterior esophagus, extending superiorly from left to right. In symptomatic patients, surgical ligation of right ductus may be performed.

Anomalous Origin of Left Pulmonary Artery

Commonly termed "pulmonary sling," this anomaly occurs when the left main pulmonary artery arises from the right main pulmonary artery rather than from the pulmonary trunk (Figure 6). The anomalous pulmonary artery traverses between the trachea and esophagus, producing mass effect along the anterior esophagus and the posterior trachea. Patients with this anomaly are often symptomatic, presenting with stridor, hypoxia, and often asymmetric lung aeration. There may be concomitant tracheal rings or tracheomalacia.

Figure 6.

6-month-old infant female with stridor. Axial CECT through the chest in soft-tissue mediastinal windows demonstrates a left pulmonary artery (arrow) arising from the right main pulmonary artery (black *) and coursing behind the trachea (white *). Findings are compatible with anomalous origin of left pulmonary artery, or "pulmonary sling."

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