LAUSR

To investigate the drainage patterns of the inferior mesenteric vein (IMV) and measure the distance from the root of the inferior mesenteric artery (IMA) to the IMV using preoperative three-dimensional computed tomography (3D-CT) angiography in patients undergoing surgery for left-sided colorectal cancer. In this retrospective study, we analyzed data collected prospectively on 167 consecutive patients who underwent laparoscopic left-sided colorectal cancer surgery between July, 2014 and August, 2019. The drainage pattern of the IMV and the distance from the root of the IMA to the IMV were evaluated using 3D-CT angiography. We also assessed intraoperative adverse events and postoperative outcomes. The IMV drained into the superior mesenteric vein (SMV) in 44 patients, into the confluence point of the SMV and splenic vein (SV) in 38 patients, into the SV in 83 patients, and into the middle colic vein in the remaining three patients. The median length from the root of the IMA to the IMV was 22.1 mm (1.3–84.9). IMV injury occurred in only one patient during surgery, but resulted in colonic ischemia. 3D-CT angiography is useful for the preoperative assessment of vascular anatomical variations of the IMV and IMA for safe intraoperative navigation and prevention of complications during laparoscopy-assisted left-sided colorectal surgery.