Anatomical basis of laparoscopic medial-to-lateral mobilization of the descending colon.

In laparoscopic colorectal resection, the medial-to-lateral approach has been largely adopted. This approach can be initiated by the division of either the inferior mesenteric artery (IMA) or the inferior mesenteric vein (IMV). This cadaveric study aimed to establish the feasibility of IMV dissection as the initial landmark of medial-to-lateral left colonic mobilization for evaluating the size of the peritoneal window between the IMV at the lower part of the pancreas and the origin of the IMA (IMA-IMV distance) and the point of origin of the IMA compared to the lower edge of the third part of the duodenum (IMA-D3 distance). These distances were recorded on 30 fresh cadavers. The IMA-D3 distance was 0.4 ± 2.2 cm (mean ± SD). The IMA originated from the aorta at the level of or below the D3 in 21 cases (70%). The IMA-IMV distance was 5.5 ± 1.8 cm and was greater or equal to 5 cm (large window) in 21 cases (70%). IMA-IMV distance was correlated with IMA-D3 showing that a large window was inversely correlated with a low IMA origin (P < 0.001). IMA-D3 distance was not correlated with weight, height and sex. IMA-IMV distance was largerin male (6.7 ± 0.9 vs. 4.9 ± 1.8, P = 0.001) and correlated with weight, (r = 0.60, 95%CI = 0.03-0.10, P < 0.001) and height (r = 0.54, 95%CI = 0.05-0.21, P = 0.002). IMV can be used as the initial landmark for laparoscopic medial-to-lateral dissection in two-thirds of cases. A too-small window can require first IMA division. The choice between the two different medial-to-lateral approaches could be made by evaluating the anatomical relationship between IMA, IMV, and D3.