Arc of Riolan-Dominant Colonic Perfusion Identified by Indocyanine Green After High Ligation of Inferior Mesenteric Artery: Critical in Preventing Anastomotic Ischemia.

Abstract

Arc of Riolan is a collateral mesenteric vessel observed in up to 17.8% of individuals1 bridging the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA) systems perfusing the descending colon besides the marginal artery. Proximal perfusion of the anastomosis after the high division of the IMA during left-sided colorectal resections is maintained by the marginal artery, but in some, this may be absent or small-caliber at the Griffiths point.2 Identification and preservation of the arc of Riolan has been associated with a decrease in acute anastomotic ischemia events requiring resection and Hartmann's procedure, although not totally eradicated the number of anastomotic leaks requiring lesser interventions.1 This video shows the vascular supply of the left colon during a robotic ultra-low anterior resection for low rectal cancer. The arc of Riolan is identified and preserved at its usual anatomical position during the isolation and division of the inferior mesenteric vein inferior to the pancreas, lengthening the descending colon for a tension free anastomosis. The arc of Riolan is temporarily occluded with an endoscopic vascular clamp after the IMA's high division. 4mg of intravenous indocyanine green (ICG) is infused to visualize the perfusion of the descending colon for 3 minutes, which is ICG's half-life.3 The fluorescence image of the descending colon is noted to be less than expected and another 3mg of ICG is infused after unclamping the arc of Riolan, revealing a visibly higher fluorescent descending colon confirming the dominant perfusion from this vessel. ICG has clearly demonstrated the arc of Riolan's dominance in perfusing the left colon. Armed with prior knowledge, its preservation can be a critical step in preventing anastomotic ischemia after IMA's high ligation in patients with potentially weak marginal artery, whilst division of a non-dominant arc of Riolan makes splenic flexure mobilization technically less challenging. See Video Abstract at http://links.lww.com/DCR/B439.