Arc of Riolan

Last revised by Dr Alex Jarema on 31 Jul 2022

The arc of Riolan, also known as the mesenteric meandering artery (of Moskowitz) or central anastomotic mesenteric artery, is an arterioarterial anastomosis between the superior and inferior mesenteric arteries.

It is an inconstant artery that connects the proximal superior mesenteric artery or one of its primary branches to the proximal inferior mesenteric artery or one of its primary branches. It is classically described as connecting the middle colic branch of the SMA with the left colic branch of the IMA. It forms a short loop that runs close to the root of the mesentery.

When present, the arc of Riolan is an important connection between the SMA and IMA in the setting of arterial occlusion or significant stenosis. In proximal SMA occlusion, the arc of Riolan provides collateral flow from the IMA to the SMA territory, and vice versa. In distal abdominal aortic occlusion, it provides collateral flow from SMA to IMA to iliac vessels (via the superior rectal artery) and then to the lower limbs (via the external iliac artery).

Both its actual existence and the general need for terms other than those mentioned in Terminologia Anatomica have been questioned by surgeons 2.

It was named after Jean Riolan (1580-1657), French anatomist, not because he discovered the vessel (there is no evidence that he did), but it was named in his honor in 1743 by the Swiss anatomist Albrecht von Haller (1708–1777) 4,5.

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Cases and figures

  • Case 1: DSA angiogram - Arc of Riolan
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  • Case 2: with abdominal aortic aneurysm
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  • Case 3: arc of Riolan (highlighted)
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  • Case 4: with IMA aneurysm
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