Re-interpreting mesenteric vascular anatomy on 3D virtual and/or physical models: positioning the middle colic artery bifurcation and its relevance to surgeons operating colon cancer

Abstract

Background: The impact of the position of the middle colic artery (MCA) bifurcation and the trajectory of the accessory MCA (aMCA) on adequate lymphadenectomy when operating colon cancer have as of yet not been described and/or analysed in the literature. The aim of this study was to determine the MCA bifurcation position to anatomical landmarks and to assess the trajectory of aMCA.

Methods: The colonic vascular anatomy was manually reconstructed in 3D from high-resolution CT datasets using Osirix MD and 3-matic Medical and analysed. CT datasets were exported as STL files and supplemented with 3D printed models when required.

Results: Thirty-two datasets were analysed. The MCA bifurcation was left to the superior mesenteric vein (SMV) in 4 (12.1%), in front of SMV in 17 (53.1%) and right to SMV in 11 (34.4%) models. Median distances from the MCA origin to bifurcation were 3.21 (1.18-15.60) cm. A longer MCA bifurcated over or right to SMV, while a shorter bifurcated left to SMV (r = 0.457, p = 0.009). The main MCA direction was towards right in 19 (59.4%) models. When initial directions included left, the bifurcation occurred left to or anterior to SMV in all models. When the initial directions included right, the bifurcation occurred anterior or right to SMV in all models. The aMCA was found in 10 (31.3%) models, following the inferior mesenteric vein (IMV) in 5 near the lower pancreatic border. The IMV confluence was into SMV in 18 (56.3%), splenic vein in 11 (34.4%) and jejunal vein in 3 (9.4%) models.

Conclusion: Awareness of the wide range of MCA bifurcation positions reported is crucial for the quality of lymphadenectomy performed. The aMCA occurs in 31.3% models and its trajectory is in proximity to the lower pancreatic border in one half of models, indicating that it needs to be considered when operating splenic flexure cancer.

Keywords: 3D printing; Accessory middle colic artery; Colonic cancer surgery; Left colectomy; Mesenteric vascular anatomy; Middle colic artery; Splenic flexure cancer.

Fig. 1

Schematic view of the middle colic artery to bifurcation with lymph nodes according to the Japanese Classification. Lymph node stations are 222 (right) following the middle colic artery (MCA) right branch, 222 (left) following the MCA left branch and 223 (central station at MCA origin). In addition, the accessory MCA is shown on the lower border of the pancreas. The solid line indicates the distance from the MCA bifurcation, via the MCA origin to the inferior mesenteric vein, the dash-dotted line indicates the standard procedure and the dotted line indicates a D2/D3 lymphadenectomy

Fig. 2

3D reconstruction of the mesenteric vascular anatomy (A) and 3D printed model of the same patient (B). GTH gastrocolic trunk of Henle, IMA inferior mesenteric artery, IMV inferior mesenteric vein, ICA ileocolic artery, MCA indicates the middle colic artery, MCV middle colic vein. The MCA bifurcation is positioned in front of the superior mesenteric artery (SMA). IMV opens into the splenic vein, left and distant to SMA. IMA arches downward, giving off the sigmoid artery. The sigmoid artery does not give off an ascending branch along the IMV. After a course of 5.8 cm, it gives off the left colic artery. In this patient, the accessory MCA is not present

Fig. 3

3D reconstruction of the mesenteric vascular anatomy in the patient with the replaced middle colic artery arising from the inferior mesenteric artery. ALCA ascending left colic artery, GTH gastrocolic trunk of Henle, ICA ileocolic artery, ICV ileocolic vein, IMA inferior mesenteric artery, IMV inferior mesenteric vein, JV jejunal vein, MCA middle colic artery, MCV middle colic vein, rMCA replaced middle colic artery, SMA superior mesenteric artery, SMV superior mesenteric vein, SV splenic vein. The MCA bifurcation is positioned right to the SMV. The IMV has a confluence into the SMV crossing the SMA anteriorly, just above the ALCA and below the SV. In this patient, the accessory MCA is not present. This anatomy is also shown in 3D virtual model 1 (Supplementary 1)

Fig. 4

Illustration of the three positions of the middle colic artery bifurcations relative to the superior mesenteric artery, the superior mesenteric vein and the pancreas. The middle colic artery bifurcation was left to the superior mesenteric vein (SMV) in 4 cases (12.1%) (a), in front of SMV in 17 cases (53.1%) (b) and right to the SMV in 11 cases (34.4%) (c)

Fig. 5

3D reconstruction of the mesenteric vascular anatomy in a patient with the accessory middle colic artery. Access. MCA indicates the accessory middle colic artery, ALCA indicates the ascending left colic artery, GTH indicates the gastrocolic trunk of Henle, IMA indicates the inferior mesenteric artery, IMV indicates the inferior mesenteric vein, JV indicates the jejunal vein, LCA indicates the left colic artery, MCA indicates the middle colic artery. The accessory MCA arises above the regular MCA origin, courses forward, then to the left, following the left colic angle vein at the lower border of pancreas. Video of this model is shown Supplementary 2.