Accessory arteries supplying the human transverse colon.

An accessory colic artery which arose from the superior mesenteric artery more proximally than the first jejunal artery and met the marginal artery at the splenic flexure was observed in 32 of 65 subjects (49.2%). Considering its constant morphological features, this accessory colic artery was given the new nomenclature 'superior left colic artery (arteria colica sinistra superior; CSS)'. The unusual middle colic artery arising from the celiac trunk was supposed to be caused by the anastomosis between the dorsal pancreatic artery from the CSS and that from the celiac trunk. An additional epiploic branch derived from the pancreatic branch (posterior epiploic branch) also sent an accessory colic artery in 2 subjects. But judging from its origin and area of distribution which overlaps with that of the middle colic artery, this accessory colic artery is not equivalent to CSS.