Arc of Riolan

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

It is an inconstant artery that connects the proximal superior mesenteric artery (SMA) or one of its primary branches to the proximal inferior mesenteric artery (IMA) 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 AOR is an important connection between the SMA and IMA in the setting of arterial occlusion or significant stenosis. In proximal SMA occlusion, the AOR provides collateral flow from the IMA to the SMA territory. In proximal IMA occlusion, it provides collateral flow from the SMA to the IMA territory. 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 mentioned in terminologica anatomica have been questioned by surgeons 2.

It is named after Jean Riolan (1580-1657), French anatomist.


Abdominal and pelvic anatomy
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Article Information

rID: 5036
Section: Anatomy
Synonyms or Alternate Spellings:
  • Riolan's arch
  • Mesenteric meandering artery
  • Central anastomotic mesenteric artery

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    Arc of Riolan

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