The incidental finding of a replaced right hepatic artery in this case is one of the more common (10-15%) variations of the celiac trunk branches. The entire hepatic artery may also arise from the superior mesenteric artery as shown above. "Normal" anatomy means the most common pattern. In general, this pattern accounts for about 70% of individuals. The norm and the two next most common patterns account for up to 99% of individuals. Benign deviations from the norm are called variations, anomalies or aberrancies. Dysfunctional variations are termed malformations.
This case also illustrates communications among the three main mesenteric arteries to the gut: the celiac, superior mesenteric and inferior mesenteric. This patient has a well developed marginal artery (of Drummond) from inferior mesenteric to the left branch of the middle colic artery. When this vessel is not complete, the splenic flexure of the colon is susceptible to ischemic injury when mesenteric circulation is compromised. When SMA or IMA is gradually narrowed, a large serpentine mesenteric collateral may develop called the meandering mesenteric artery (arc of Riolan). The pancreaticoduodenal arcades connect the celiac and SMA circulations.
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