D uring embryonic life, events may alter the normal growth and fusion of the endocardial tube, the paired dorsal aortae, and the vitelline plexus, leading to anomalies and variants of the mature axial arterial system. 1 Many of these are well known, especially those associated with the aorta, heart, and umbilical artery. 1,2 Vitelline variants have also been found that are either associated with Meckel diverticulum or caudal regression syndrome. 3,4 We present a case of anomalous intercostal arterial supply, which, to our knowledge, has not been reported previously. The aberrant intercostal trunk is associated with aberrant descending thoracic aorta position, a replaced common hepatic artery from the superior mesenteric artery, and an isolated splenic artery origin from the aorta.A 27-year-old man with a medical history of irritable bowel syndrome and stage I hypertension presented for renal vasculature evaluation. A renal arterial magnetic resonance angiogram (not shown) and subsequent thoracoabdominal computed tomography (CT) angiogram [64-row multidetector-row computed tomography (MDCT), 1.0-mm section thickness after intravenous injection of 600 mgI/kg Isovue 370] demonstrated normal renal arteries and an anomalous branch artery arising from the posterior aspect of the aorta at the level of T12 with median ascension, terminating at T3. The artery gradually tapered from its 7-mm diameter origin to its terminus and supplied the third through twelfth intercostal arteries bilaterally (Figure 1). This "anomalous intercostal trunk" coursed between the thoracic spine and the descending thoracic aorta, which was elevated 23 mm anterior to the thoracic vertebral bodies and was in close association with the esophagus (Figure 2). An additional posterior trunk arose at the level of T6 and ascended superiorly to supply the first and second intercostals spaces. Associated with this anomaly was an isolated splenic artery Figure 1. Frontal volume-rendered CT angiogram demonstrates the T4 -T12 intercostal arteries arising from the anomalous intercostal trunk arising from the aorta at the T12 level (arrow). Figure 2.Transverse CT section demonstrates centralized apices of the hemidiaphragms. In the upper abdomen, the aorta (A) is anteriorly displaced from the vertebrae and the anomalous trunk (curved arrow) occupies the prevertebral space. Fat occupies the space in the middle mediastinum between the aorta and vertebrae. The online-only Data Supplement is available at http://circimaging.ahajournals.org/cgi/content/full/2/6/e49/DC1.

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