Re-interpreting mesenteric vascular anatomy on 3D virtual and/or physical models, part II: anatomy of relevance to surgeons operating splenic flexure cancer

Abstract

Background: The splenic flexure is irrigated from two vascular areas, both from the middle colic and the left colic artery. The challenge for the surgeon is to connect these two vascular areas in an oncological safe procedure.

Materials and methods: The vascular anatomy, manually 3D reconstructed from 32 preoperative high-resolution CT datasets using Osirix MD, Mimics Medical and 3-matic Medical Datasets, were exported as STL-files, video clips, stills and supplemented with 3D printed models.

Results: Our first major finding was the difference in level between the middle colic and the inferior mesenteric artery origins. We have named this relationship a mesenteric inter-arterial stair. The middle colic artery origin could be found cranial (median 3.38 cm) or caudal (median 0.58 cm) to the inferior mesenteric artery. The lateral distance between the two origins was 2.63 cm (median), and the straight distance 4.23 cm (median). The second finding was the different trajectories and confluence pattern of the inferior mesenteric vein. This vein ended in the superior mesenteric/jejunal vein (21 patients) or in the splenic vein (11 patients). The inferior mesenteric vein confluence could be infrapancreatic (17 patients), infrapancreatic with retropancreatic arch (7 patients) or retropancreatic (8 patients). Lastly, the accessory middle colic artery was present in ten patients presenting another pathway for lymphatic dissemination.

Conclusion: The IMV trajectory when accessible, is the solution to the mesenteric inter-arterial stair. The surgeon could safely follow the IMV to its confluence. When the IMV trajectory is not accessible, the surgeon could follow the caudal border of the pancreas.

Keywords: D3 mesenterectomy; Inferior mesenteric artery; Left colectomy; Mesenteric vascular anatomy; Middle colic artery; Splenic flexure cancer.

Fig. 1

Distance A: From the MCA origin to the IMA origin. Distance B: Parallel to the aorta axis from the IMA origin to the transverse plane through the MCA origin. Distance C: In the transverse plane from the MCA origin to the intersection with Distance B. The angle between the Distance A and Distance B intersection was named Angle AB Vessels MCA middle colic artery, SMA superior mesenteric artery, IMA inferior mesenteric artery

Fig. 2

The 3D-printed vascular model gives valuable visual and tactile information as the surgeons can view the anatomy from different angles while holding the model in her/his own hands

Fig. 3

A CT reconstruction visualizing the mesenteric inter-arterial stair in two patients. A An MCA origin cranial to the IMA origin implies a positive Distance B (yellow) and that Distance A (green) points from the IMA origin cranioventrally towards the MCA origin. Distance C (red) represents the height of the stair. In this patient Distance A was 4.23 cm, Distance B 4.07 cm, Distance C 1.16 cm and the angle between Distance A and B 15.9 degrees. B An MCA origin caudal to the IMA origin implies a negative Distance B (yellow) and that Distance A (green) points caudoventrally. In this patient Distance A was 2.34 cm, Distance B − 0.58 cm, Distance C 2.26 cm and the angle between Distance A and B 75.6 degrees Vessels aMCA accessory middle colic artery, MCA middle colic artery, SMA superior mesenteric artery, IMA inferior mesenteric artery (Color figure online)

Fig. 4

Confluence patterns of the inferior mesenteric vein (IMV) to the portal vein flow. Each pathway is illustrated with an actual reconstruction and a schematic illustration. In addition, a 3D printed model is shown for comparison in (Fig. 3B). A IMV joining the splenic vein (11 patients), B IMV joining the superior mesenteric vein (18 patients), C IMV joining a jejunal vein (three patients) Vessels SMV superior mesenteric vein, SMA superior mesenteric artery, GTH gastrocolic trunk of Henle, MCV middle colic vein, MCA middle colic artery, RCA right colic artery, ICV ileocolic vein, ICA ileocolic artery, JV jejunal vein, SV splenic vein, IMV inferior mesenteric vein, IMA inferior mesenteric artery, LCA left colic artery

Fig. 5

3D reconstruction (A) and schematic 3D illustration (B) showing the inferior mesenteric vein (IMV) confluence into splenic vein (SV). Note the trajectory of the splenic vein along the pancreatic border Vessels SMV superior mesenteric vein, MCA middle colic artery, SMA superior mesenteric artery, JV jejunal vein, ALCA ascending left colic artery

Fig. 6

Illustration of “the mesenteric inter-arterial stair”. The stair (purple) ascends from the IMA to the MCA origin. The small bowel mesentery is marked with translucent blue, and the lymph node stations are numbered according to the Japanese classification [11], the central lymph node station belonging to the aMCA is additionally named a223 to distinguish it from 223 belonging to MCA Vessels MCA middle colic artery, aMCA accessory middle colic artery, ICA ileocolic artery, ICV ileocolic vein, SMV superior mesenteric vein, SMA superior mesenteric artery, IMA inferior mesenteric artery, LCA left colic artery, IMV inferior mesenteric vein, ALCA ascending left colic artery, DLCA descending left colic artery (Color figure online)

Fig. 7

The mesenteric inter-arterial stair with positive (A) and negative (B) longitudinal distance. The dissection line is the black dashed line following IMV towards SMV, turning towards right at the lower border of pancreas (if IMV goes retropancreatically) and ending at the MCA origin. The stair is visualized as a triangle, with the height (lateral distance) indicated Vessels MCA middle colic artery, aMCA accessory middle colic artery, ICA ileocolic artery, ICV ileocolic vein, SMV superior mesenteric vein, SMA superior mesenteric artery, IMA inferior mesenteric artery LCA left colic artery