[Riolan's arcade: hemodynamic importance--therapeutic deductions].

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. In addition, when a patient known to suffer from arteritis has to undergo surgery involving the rectosigmoid area, a preliminary arteriography is necessary: the presence of a hypertonic arcade of Riolan requires special therapy since untimely ligature of this artery would provoke lethal ishcemia of the colonic wall. Examination of the arteriogram affords the surgeon some indication of the state of the splanchnic circulation, and he can then take the necessary precautions to prevent any risk of postoperative development of necrosis of the left colon.