39 year old woman presents with shortness of breath

Right-side aortic arch

Absent left pulmonary artery with prominent left bronchial arteries.

Septal thickening and peripheral honeycombing within the left lung.

 Right aortic arch with aberrant left subclavian artery and unilateral pulmonary artery agensis.

A right aortic arch occurs in approximately 0.1% of people. There are four subtypes with the most common occurring with an aberrant left subclavian artery. The second most common has mirror-image branching. The third most common demonstrates an isolated left subclavian artery, and the least common an aberrant left brachiocephalic artery.  A right aortic arch with aberrant left subclavian artery occurs as a result of interruption of the embryonic left aortic arch between the left CCA and left subclavian artery. It is the second most common cause of a vascular ring following double aortic arch. There is an association with congenital heart disease in 5-12% of cases.

            Unilateral absence of a pulmonary artery is a rare occurrence which can affect the right or left side. It is believed to occur as a result of a failed connection between the sixth aortic arch and the pulmonary trunk. Fraentzel first described the finding in 1868 and stated that 30% of these patients can remain asymptomatic until adulthood. Absence of the left pulmonary artery has been reported to be associated with multiple cardiac defects including tetralogy of Fallot, atrial septal defect, coarctation of aorta, right aortic arch, and Eisenmenger's syndrome. Ryu reported in 2004 that the lung findings in cases of unilateral agenesis of a pulmonary artery included reticular opacities, septal thickening, subpleural consolidation, cystic lung changes, and pleural thickening.

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Ryu D, et al. HRCT Findings of Proximal Interruption of the Right Pulmonary Artery. Journal of Thoracic Imaging: July 2004;19(3):171-175.

Sharma A, Bieuei, F, Dillon E. Agenesis of the left pulmonary artery, with patent ductus arteriosus and hypoplasia of the left lung. Applied Radiology. June 2004; 33(6).