Background

The Arc of Riolan (AoR) is known to provide collateral vascularization between the Superior Mesenteric Artery (SMA) and the Inferior Mesenteric Artery (IMA), yet inconsistent definitions regarding the artery’s course exist. The AoR is a highly contested and confusing collateral artery among existing gastrointestinal arteries. The identification and preservation of the AoR is crucial to reducing the risk of acute colonic ischemia following splenic procedures. However, more details about the AoR prevalence and pattern are needed to corroborate the likelihood of finding this collateral artery in a patient. This study aimed to explore the prevalence and pattern of the AoR as defined by a connectionbetween the Middle Colic Artery (MCA) and Ascending Left Colic Artery (ALCA).

Methods A total of fifty-two cadaveric colons were dissected at Tilman J. Fertitta Family College of Medicine and Baylor College of Medicine. Specific dissection techniques were employed to expose the ascending, transverse, and descending colon, and associated vasculature. AoR patterns were observed and photographed in all the donors. Photographic analysis followed dissection to determine whether a connection between the MCA and ALCA was present.

Results The AoR was identified in six bodies (11.5%) as a smaller artery forming collateral circulation between the Ascending Left Colic Artery off the IMA and the Middle Colic Artery off the SMA. The AoR was thin in nature when compared with SMA and IMA arterial branches. The authors of this study hypothesize that corroborating previous Arc studies with additional prevalence data regarding the AoR connection will encourage and assist with the identification and preservation of the Arc during colonic procedures.

Conclusion The AoR was identified in 11.5% of the colons examined and the artery’s course was noted. The frequency of the connection identified in this study matches existing AoR prevalence studies. Additional samples will be collected to determine the statistical significance of this pilot study. Vasculature and anastomotic connections among the transverse and descending colon are highly variable from patient to patient; however, surgeons must be aware of a collateral artery that connects the MCA with the ALCA, given that its frequency is about 11% among patients. Proper identification and preservation of the AoR could prevent post-operative ischemia following bowel resection.