CT Imaging Features Of Aberrant Subclavian Artery: A Systematic Study Of 173 Cases

Objective:To acknowledge the morphological classification of aberrant subclavian artery(ASA) and report the incidence of ASA associated with complications, to summarize the imaging differences between aberrant right subclavian artery(ARSA)and aberrant left subclavian artery(ALSA) by analyzing their imaging features in CT.Methods: ASA diagnosed by CT between February 2011 and November 2015 in Wuhan Union Hospital was retrospectively analyzed by reviewing CT images and was divided into two groups : plain CT group and contrast-enhanced CT/CT angiography(CECT/CTA) group. Imaging features of ASA were summarized by observing the relationship between its opening and aorta, its pathway and adjacent tissues such as trachea and esophagus and observing the complications such as tracheal and esophageal compression.Results:Of 173 cases, 132(76.3 %) were ARSA and 41(23.7%) were ALSA. All the ASA traversed the mediastinum posterior to the esophagus, resulting in esophageal compression shown on CT. In ARSA, 1(0.8%) was associated with tracheal compression shown on CT. 5(3.8%) were associated with aortic dissection or intramural hematoma(1 with type-A intramural hematoma, 2 with type-A dissection and 2 with type-B dissection), of which 3(2 type-A dissection and 1 type-B dissection)involved ARSA. Primary aneurysms of ARSA were seen in 3 cases(2.3%), and two of them involved the origination of ARSA. 34 cases(25.8%) were associated with Kommerell's diverticulum(KD), and the mean size of KD was 1.58cm(rang from1.2cm to 2.0cm). The ratios of KD to ARSA in size were 1.78(plain CT group) and1.91(CECT/CTA group). In ALSA, the percentage of tracheal compression in ALSA(43.9%, 18 cases) was significantly higher than ARSA. 1 case(2.4%) was associated with proximal descending aortic aneurysm. ALSA had a significantly higher rate(90.2%, 37 cases) associated with KD than ARSA. The mean size of KD in ALSA(2.64 cm, range between 1.8cm and 4.8cm) was significantly larger than KD in ARSA.The ratios of KD to ALSA in size were 2.93(plain CT group) and 3.05(CECT/CTA group), which were significantly larger than ARSA`S.Conclusion: ASA usually runs posterior to the esophagus and ARSA is more common than ALSA. ALSA has a higher rate associated with tracheal compression and KD than ARSA, and KD of the former is larger in size and more obvious in the expansive degree than the latter. CT is the best examination to diagnose ASA.