Colorectal cancers and ovarian cancers are respectively the 2nd and 5th cause of cancer mortality in France. Surgical resection is a crucial step in the therapeutic management of colorectal cancers. For advanced ovarian cancers, the objective of cytoreductive surgery is to obtain complete macroscopic resection with no visible residual disease. One or more digestive resections are often required to achieve this goal of complete surgery (usually a modified posterior pelvic exenteration with colorectal resection). A ligation of the inferior mesenteric artery at its origin is classically performed in left colectomies and rectal resection for colorectal cancers. This allows the resection of the colorectal segment with a complete mesocolic lymphadenectomy until the origin of the inferior mesenteric artery and a good mobilization of the descending colon to allow its anastomosis to the underlying rectal stump. This ligation of the inferior mesenteric artery at its origin is also frequently performed in cases of modified posterior pelvic exenteration for ovarian cancer. Recently, several studies suggest that arterial ligation of the inferior mesenteric artery could be performed below the emergence of the left colic artery. Its preservation requiring a meticulous vascular dissection would allow a better vascularization of the descending colon and of the colorectal anastomosis without affecting the carcinologic quality of the resection and the number of resected lymph-nodes. Indeed, the most feared complication during colorectal anastomosis is the anastomotic leakage whose rates are on average 15% in rectal cancer with low anastomosis and 6% in ovarian cancers. Verifying the adequate vascularization of the descending colon before performing the colorectal anastomosis is a crucial step in reducing the risk of postoperative fistula. However, quantifying this vascularization is challenging, and several techniques can be used to assess it. The gold standard technique involves measuring arterial pressure using a catheter inserted into the marginal artery of the descending colon. Other non-invasive techniques also use Doppler studies to calculate pressure in the marginal artery or assess oxygen saturation using a sterile sensor. Studies have shown that the use of indocyanine green in colorectal surgery, particularly to evaluate perfusion before the creation of an anastomosis, significantly reduces the rate of anastomotic leakage. Indocyanine green is a fluorescent dye that, after intravenous injection, binds to plasma proteins and allows tissue perfusion to be visualized using a fluorescence system. The objective of this project is to show that the preservation of the left colic artery is possible and allows a better vascularization of the descending colon before colorectal anastomosis.