The relation between inferior mesenteric vein ligation and collateral vessels to splenic flexure: Anatomical landmarks, technical precautions and clinical significance

Purpose: Our aim to assess clinical significance of the relation between inferior mesenteric vein ligation and collateral blood supply (meandering mesenteric artery) to the splenic flexure with elaboration more in anatomical landmarks and technical tips. Materials and Methods: We review the literature regarding the significance of the collateral vessels around inferior mesenteric vein (IMV) root and provide our prospective operative findings, anatomical landmarks and technical tips. We analyzed the incidence and pattern of anatomic variation of collateral vessels around the IMV. Results: A total of 30 consecutive patients have been prospectively observed in a period between June 25-2012 and September 7-2012. Nineteen males and eleven females with mean age of 63 years. Major colorectal procedures were included. There were three anatomical types proposed, based on the relation between IMV and the collateral vessel. Type A and B in which either the collateral vessel crosses or runs close to the IMV with incidence of 43.3% and 13.3%, respectively, whereas type C is present in 43.3%. There was no definitive relation between the artery and vein. No intra or postoperative ischemic events were reported. Conclusion: During IMV ligation, inadvertent ligation of Arc of Riolan or meandering mesenteric artery around the IMV root "in type A&B" might result in compromised blood supply to the left colon, congestion, ischemia and different level of colitis or anastomotic dehiscence. Therefore, careful dissection and skeletonization at the IMV root "before ligation if necessary" is mandatory to preserve the collateral vessel for the watershed area and to avoid further injury.