Superior mesenteric vessel anatomy features differ in Russian and Chinese patients with right colon cancer: computed tomography-based study

Abstract

To the Editor: The literature has registered a considerable interest among Western surgeons in the role of extended lymph node dissection in right hemicolectomy. There are a lot of voices of dissent regarding the harvest of nodes lying dorsally to the superior mesenteric vein (SMV) and superior mesenteric artery (SMA).[1] The colic branches of the SMA are usually represented by the ileocolic artery (ICA), middle colic artery (MCA), and right colic artery (RCA). The latter was present in 60.0% (95% confidence interval 0.454–0.741) patients.[2] The position of SMA branches in relation to the SMV plays a key role in safe D3 lymph node dissection. Reaching the origin of SMA branches is technically more difficult if they lie dorsally to the SMV. Computed tomography (CT) is a reliable method for evaluating the involvement of adjacent structures and detecting metastasis in the liver, lungs, or other organs. It is recommended as a part of the pre-operative assessment of colon cancer.[3] CT scanning with intravenous contrast makes it possible to perform a thorough study of the anatomy of colon vessels.[4] Anatomical variations have been evaluated by researchers from Asia, Europe, and North America, and their findings suggest that some ethnic differences could exist among groups.[5] Nevertheless, the literature lacks a direct comparative study regarding the vascular anatomy of the right colon in different ethnicities. The purpose of this study was to compare the frequency of SMA branches and variants of relative position with respect to SMA and SMV in Russian and Chinese patients. A retrospective analysis was carried out on prospectively collected data of all consecutive right colon cancer patients who underwent laparoscopic or robotic right hemicolectomy with D3 lymph node dissection at the Beijing Clinic, China and Moscow Clinic, Russia, between 2016 and 2018. All human studies have been reviewed by the appropriate ethics committee and have, therefore, been performed in accordance with the ethical standards laid down in an appropriate version of the 1965 Declaration of Helsinki. Right colon cancer was defined as cancer located in the appendix, cecum, ascending colon, or hepatic flexure. Patients who had previously undergone major abdominal resections by laparotomy or whose CT scans were unclear or incomplete were excluded. MCA was defined as the most cranial artery arising from the SMA and supplying to the transverse colon. The ICA was considered the most caudal colic branch of the SMA that supplies to the cecum, ileum, and appendix. RCA supplies to the ascending colon. For the purposes of this study, we defined the RCA as a vessel originating directly from the SMA between the ICA and MCA. However, this vessel reportedly has other types of origin, for example, a common trunk with either the MCA or the ICA; in this study, these types of vessel branching were not regarded as RCA. Cases where RCA as a separate trunk originating from the SMA could not be found were recorded as “RCA missing.” Cases where MCA as a separate trunk originating from the SMA could not be found were recorded as “MCA missing.” Considering that the MCA always runs ventrally to the SMV, whereas RCA and ICA can run either ventrally or dorsally to the SMV, six types of arterial-venous interactions were defined. Therefore, two major types of vessel interactions were defined based on ICA position: Type Ia-ICA lies ventrally, RCA is absent, and MCA lies ventrally; Type Ib-ICA lies ventrally, RCA lies ventrally, and MCA lies ventrally; Type Ic-ICA lies ventrally, RCA lies dorsally, and MCA lies ventrally; Type IIa-ICA lies dorsally, RCA is absent, and MCA lies ventrally; Type IIb-ICA lies dorsally, RCA lies dorsally, and MCA lies ventrally; Type IIc-ICA lies dorsally, RCA lies ventrally, and MCA lies ventrally. Qualitative data were analyzed with a Chi-squared test, Fisher exact test (two samples, unpaired), or the McNemar test (two samples, paired). The Wilcoxon signed-r