Anastomotic fistulas are the main cause of morbidity and mortality in colorectal surgery. They are responsible for septic complications, leading to increased mortality, local recurrence, repeat surgery and impaired sexual, urinary and digestive function. Fistulas are multifactorial; among the causes, colonic vascularization seems to be a major one. Ligation of the inferior mesenteric artery during rectal surgery has been shown to reduce intraoperative colonic perfusion flow. The left colon is then vascularized only by the colonic border arcade, perfused by the superior mesenteric artery. Ischemic pre-conditioning of the arterial network prior to surgery should ensure better vascularization by developing arterial collaterality and increasing perfusion flow in the colonic border arcade. In view of major advances in interventional radiology, this preconditioning could be achieved by endovascular ligation of the inferior mesenteric artery (IMA), based on the same principle as during surgery: proximal occlusion of the inferior mesenteric artery (IMA), using embolization material (plug or coils), 3 weeks before surgery, to allow the colonic border arcade to develop. We carried out a single-center pilot study (AMIREMBOL 1, NIMAO 2017; Frandon et al. 2022) to assess the feasibility of ischemic preconditioning of the colon for patients with rectal or sigmoid cancer. The study included 10 patients, randomized into two groups: the control group, with preoperative arteriography and standard management and the "embolization" group, with embolization of the IMA three weeks prior to surgery. IMA embolization was successfully performed in all 5 patients in the embolization group, with no major complications. The effect on colonic perfusion, measured by intraoperative Doppler directly on the border arch, with recording of resistance indexes (independent of measurement angle), showed a drop in resistance indexes in the control arm, after ligation of the IMA, which persisted after 5 minutes. In the "Embolization" arm, no drop in this index was reported during surgery, reflecting good development of vascular collaterality and at least relative acute ischemia of the colon after IMA ligation during surgery. Finally, in the "control" group, one anastomotic fistula was reported after surgery and required re-operation. There were no fistulas in the embolization group.

The present study (AMIREMBOL 2) will investigate the safety of IMA embolization prior to rectal surgery, according to IDEAL recommendations (Lancet 2009). Its aim is to assess the safety of endovascular embolization of the IMA prior to surgery in patients with rectal tumors, and to estimate the potential benefits in terms of time to surgery and the occurrence of post-operative fistulas.

The study will also assess the impact of subacute ischemia induced by IMA embolization on colonic vasculature remodeling, colonic ischemic suffering, altered hemostasis and initiation of neo-angiogenesis through blood sampling kinetics.

The hypothesis is that ischemic preconditioning by inferior mesenteric artery (IMA) embolization prior to rectal cancer resection surgery is safe and will result in a decrease in acute relative colon ischemia and a reduction in the rate of fistulas and post-surgical complications. The hypothesis is that the beneficial effects of the ischemic preconditioning of IMA will be due to better blood perfusion of the colon at 3 weeks, which is apparently linked to remodeling and/or the development of collateral vascularization.