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 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 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.
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She had no history of jaundice or melena. On examination, abdomen was soft with no organomegaly. Laboratory workup showed anaemia with haemoglobin 8.
Contrast-enhanced CT abdominal angiography revealed severe occlusive atherosclerotic aortoiliac disease, non-visualization of infrarenal abdominal aorta with Arc of Riolan AOR connecting superior mesenteric and inferior mesenteric arteries SMA and IMA Figs. She was put on antispasmodics and was advised for endovascular surgery.
However, the patient has refused surgery and is on follow up. Volume-rendered 3D CT angiography image better depicting large mesenteric collateral Arc of Riolan arrow.
CT angiography is the investigation of choice in such cases as it can visualize surrounding organs, minimally invasive, allows 3D image reformatting and has a higher sensitivity and specificity 2. Another such collateral is the marginal artery of Drummond. Identification of this rare anatomic variation is important for intervention radiologists.
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This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3. This article has been cited by other articles in PMC. Open in a separate window. References 1. The variant blood supply to the descending colon, rectosigmoid and rectum based on dissections.
Arc of Riolan
The hemodynamic significance of the arcade of Riolan has been analysed. This arterial arcade provides an anastomosis between the territories of the superior and inferior mesenteric arteries. The arcade is only clearly visible on arteriography when an obstacle is present at one of its extremities or when it is being used for revascularization of the lower limbs. The discovery during surgery or on X-ray of a dilated arcade of Riolan presents a hemodynamic problem when the continuity of a digestive artery must be reestablished.
[Riolan's Arcade: Hemodynamic Importance--Therapeutic Deductions]
The arterial arcades intermesenteric arterial anastomoses or Riolan arcades  are a series of anastomosing arterial arches between the arterial branches of the jejunum and ileum. Nearest the duodenum the mesenteric loops are primary, the vasa recta are long and regular in distribution, and the translucent spaces lunettes are extensive. Toward the ileocolic junction , secondary and tertiary loops are observed, the vessels are smaller and become obscured by numerous fat-tabs. The diagrams below show the arrangement and variations of the loops of the mesenteric vessels for various segments of the small intestine of average length:. Loop of small intestine showing distribution of intestinal arteries. From Wikipedia, the free encyclopedia.
In human anatomy, the marginal artery of the colon , also known as the marginal artery of Drummond and artery of Drummond is an artery that connects the inferior mesenteric artery with the superior mesenteric artery. It is sometimes absent, as an anatomical variant. This artery is almost always present and its absence should be considered a variant. Along with branches of the internal iliac arteries , also known as Cherbanyk's arteries, it is usually sufficiently large to supply the oxygenated blood to the large intestine covered by the inferior mesenteric artery and is a reason that in abdominal aortic aneurysm repair the inferior mesenteric artery does not have to be re-implanted re-attached into the repaired abdominal aorta.