In colon cancer surgery, CME, which involves ligation and dissection of the major colorectal vessels at the root and en bloc resection of the mesentery, is a standard technique. CME is required to reduce the risk of recurrence and to improve long-term outcomes. CME is important for reducing the risk of local recurrence and unexpected bleeding after colon cancer surgery. However, proper artery ligation of the right-side colon may be difficult due to variations in arterial vasculature. A previous study examined the occurrence of vascular variations in patients undergoing radical right hemicolectomy and noted that a failure to detect such variations may cause unexpected bleeding [4]. Therefore, it is important to confirm any vascular variations in the right colon. The present case had a rare vascular variation in which the MCA and ICA had a common trunk. Sharing this discovery will raise awareness of such variations and aid surgeons when conducting right colon cancer surgery.

Most reports of variations in the right-sided colic artery dealt with the origin and defects of each branch. In a meta-analysis of 4,691 cases by Robert et al [6], the ICA, RCA and MCA were present in 99.7% (95% CI 99.4%–99.8%), 72.6% (95% CI 61.3%–82.5%) and 96.9% (95% CI 94.2%–98.8%) of patients, respectively. The RCA shared a common trunk with the ICA and MCA in 13.2% and 17.7% of patients, respectively. In the present case, the MCA and ICA were present, but the RCA was absent.

Gamo et al [7] examined 50 cadavers and 560 CTs, and propose that the SMA has four branching patterns (patterns I to IV): Pattern I, the MCA, RCA, and ICA arise separately from the SMA; Pattern II, the three right branches of the SMA arise from a common trunk; Pattern IIa, the MCA and RCA arise from a common trunk; Pattern IIb, the ICA and RCA arise from a common trunk; Pattern IIc, the three arteries arise from a common trunk; Pattern III, the RCA is not present; and Pattern IV, the RCA is found as an accessory branch. Using this classification, the present case conformed to Pattern IIc, which accounted for 2 of 560 (0.35%) cases in their study. The cases of the MCA having a common trunk with the ICA [7,8,9] are summarized in Table 1; seven cases, including the present case, have been reported, in which the RCA was absent in three.

The MCA supplies blood to the transverse colon and typically (> 97% of cases) arises from the SMA [5, 10]. An MCA origin anomaly is extremely rare, and few cases have been reported in the literature [10,11,12,13,14,15] (Table 2).

If the anatomy of the vasculature is unknown preoperatively, lymphadenectomy may be inadequate, and bleeding may occur due to vascular injury. Recently, with the widespread use of multi-slice CT for high-resolution imaging using a slice thickness of 1 mm along with image construction software, constructing vascular images and obtaining preoperative information on the arterial bifurcation pattern have become easier. Preoperative 3D-CT reportedly has high sensitivity, specificity, accuracy, and reliability in establishing mesenteric vessel anatomy. Nonetheless, false-negative and false-positive CT findings do occur. Nesgaard et al. [16] reported a diagnostic accuracy of 97.1%, sensitivity of 85.7%, and specificity of 95.2% for preoperative CT image reconstruction of surgical findings or resected specimens. Intraoperative confirmation may be necessary, since preoperative imaging may be inaccurate, particularly in patients with a higher body mass index. In the present case, preoperative multi-slice CT and intraoperative ICG fluorescence imaging with the overlay function (for confirmation of the vascular branching observed on CT) were conducted to perform the surgery without complications.

ICG fluorescence imaging is widely used in gastrointestinal surgery and is considered useful for reducing anastomotic leakage [17]. In the present case, ICG fluorescence imaging was used to identify the artery, not to evaluate the colonic blood flow. PubMed was searched using “ICG”, “intraoperative”, and “artery” as keywords, and no reports of intraoperative ICG examinations to confirm the courses of the colonic vessels were found. In the present case, the colic arteries were clearly visualized with ICG fluorescence imaging; therefore, this method would be useful for determining the optimal vessel resection, especially with abnormal variation of vessels.