The Right Inferior Phrenic Artery: Origin and Proximal Anatomy on Digital Subtraction Angiography and Thin-section Helical Computed Tomography

Abstract

PURPOSE: To investigate the origin sites of the right inferior phrenic artery (RIPA) and its proximal anatomy with use of digital subtraction angiography (DSA) and thin-section computed tomography (CT). MATERIALS AND METHODS: Among 2,593 patients, selective RIPA arteriography was attempted in 591 (507 men; mean age, 54 years) who underwent chemoembolization and thin-section liver CT. CT and DSA images were reviewed. RESULTS: The origin sites of the RIPA and its proximal segment were analyzed on DSA and CT in 580 patients after 11 were excluded because of a completely occluded or unidentifiable RIPA. The RIPA originated directly from the aorta in 336 patients (57.9%) and from the major visceral aortic branches in 244 (42.1%). In RIPAs of aortic origin, the most common level was the supraceliac aorta (n = 119, 35.4%), and the mean angular orientation slightly deviated to the left side of the aorta (12.1 degrees). As the level of origin became lower (from "juxtaceliac" to suprarenal), there were two groups in whom the RIPAs arose around an oblique path from the supraceliac aorta to the right renal artery (n = 199; 59.2%) or left renal artery (n = 18; 5.4%). When the RIPA origin was draped by the diaphragm (n = 197; 58.6%), its proximal segment showed a downward and/or leftward impression or an acute rightward turn depending on its level of origin and angular orientation. Unusually, three RIPAs under the right hemidiaphragm. exhibited a transdiaphragmatic course. CONCLUSIONS: RIPAs had diverse proximal anatomy relative to their origin level and overhanging diaphragmatic crus, which could be evaluated with thin-section helical CT.