Diagnostic dilemma: left aortic arch with right descending aorta--a rare vascular ring.

An infant had a rare type of vascular ring comprising a left aortic arch, a retroesophageal transverse aorta, a right descending aorta, and a right ligamentum arteriosum. Noninvasive studies including echocardiography with Doppler color flow mapping and magnetic resonance imaging were diagnostic of a vascular ring. However, only angiography prospectively established the exact type of ring. This report discusses the pitfalls of noninvasive studies used to diagnose unusual arch anomalies.