A rare case of aneurysm of arc of riolan artery and gastroduodenal artery

Abstract

Arc of Riolan is a collateral channel that connects the proximal superior mesenteric artery (SMA) or its middle colic branch and the proximal inferior mesenteric artery or its left colic branch in case of stenosis of either of the arteries. A 65-year-old diabetic female presented with vague abdominal pain. Ultrasonography showed a large aneurysm within the abdomen in the left lumbar region. Computed tomography (CT) angiography done showed severe diffuse atherosclerotic calcification of the abdominal aorta with complete occlusion of the celiac trunk and mild stenosis of SMA origin. The arc of Riolan was seen between the middle colic artery and the ascending branch of the left colic artery, with a large saccular aneurysm in its mid section. No evidence of rupture or hematoma was visible. Another saccular aneurysm was also seen involving the gastro-duodenal and the pancreatico-duodenal collateral arcade. As far as we know, this is the first case of arc of Riolan artery aneurysm to be reported in English literature.

Keywords: Aneurysm; arc of Riolan; computed tomography.

Dr. Kumaresh Athiyappan

Figure 1

65-year-old woman with pain in the abdomen diagnosed due to arc of Riolan aneurysm. Ultrasound of the abdomen with color Doppler shows a large saccular aneurysm (arrowhead) within the abdomen in the left lumbar region. Color Doppler shows swirling blood flow within it. No thrombus was seen.

Figure 2

65-year-old woman with pain in the abdomen diagnosed with arc of Riolan aneurysm. (a) CT scan – sagittal maximum intensity projection (MIP) in arterial phase shows occlusion of the celiac origin (asterix) with diffuse atherosclerotic calcifications in the abdominal aorta. (b) CT scan – axial section in the arterial phase at the level of SMA origin shows a calcific plaque at the origin causing ~50% diameter stenosis (left arrow). Also seen is the arc of Riolan aneurysm (arrowhead).

Figure 3

65-year-old woman with pain in the abdomen diagnosed with arc of Riolan aneurysm. a) CT scan – coronal maximum intensity projection (MIP) in the arterial phase of abdomen shows the arc of Riolan with aneurysm (arrowhead) and gastroduodenal artery aneurysm (down arrow). b) CT scan volume-rendered imaging in arterial phase shows the arc of Riolan with aneurysm (arrowhead) and gastroduodenal artery aneurysm (down arrow).

Figure 4

65-year-old woman with pain in the abdomen diagnosed due to arc of Riolan aneurysm. CT scan arterial phase volume-rendered imaging shows the arc of Riolan (red shaded) between the SMA (left arrow) and the IMA (right arrow), with an aneurysm seen in its mid part (curved arrow).