Objective:To investigate the application value of mesocolon approach in transanal total mesorectal excision (TaTME).Methods:The retrospective cohort study was conducted. The clinicopathological data of 61 patients with middle or low rectal cancer who were admitted to the Nanchong Central Hospital of North Sichuan Medical College from January to December in 2018 were collected. There were 41 males and 20 females, aged from 43 to 81 years, with an average age of 62 years. Of the 61 patients, 30 patients undergoing TaTME with the conventional approach were allocated into traditional approach group, and 31 patients undergoing TaTME with mesocolon approach were allocated into mesocolon approach group. Observation indicators: (1) surgical situations; (2) postoperative recovery; (3) follow-up. Follow-up was conducted by outpatient examination and telephone interview once every 3 months to detect local recurrence and metastasis of tumors in patients up to June 2019. Measurement data with normal distribution were expressed as Mean± SD, and comparison between groups was conducted using the t test. Measurement data with skewed distribution were expressed as M (range), and comparison between groups was conducted using the Mann-Whitney U test. Count data were expressed as absolute numbers or percentages, and comparison between groups were analyzed using the chi-square test or Fisher exact probability. Comparison of ordinal data between groups was analyzed using the Mann-Whitney U test. Results:(1) Surgical situations: patients in the two groups underwent TaTME successfully, without conversion to laparotomy. The transabdominal operation time, volume of intraoperative blood loss, length of distal margin from surgical specimen, length of proximal margin from surgical specimen, cases with complete mesentery or with nearly complete mesentery ( the integrity of mesentery ), positive rate of circumferential margin, positive rate of distal margin, and the number of lymph node dissected of the traditional approach group were (126±56)minutes, 41.0 mL (range, 17.5-71.4 mL), 1.3 cm (range, 0.8-2.0 cm), (10.0±5.0)cm, 10, 20, 3.3%(1/30), 0, 13.7 (range, 9.0-17.0), respectively, versus (101±30)minutes, 44.0 mL (range, 25.0-67.5 mL), 1.6 cm (range, 1.1-2.2 cm), (12.0±3.0)cm, 23, 8, 6.5%(2/31), 0, 13.0 (range, 10.9-17.3) of the mesocolon approach group. There were significant differences in the transabdominal operation time, length of proximal margin from surgical specimen, and the integrity of mesentery between the two groups ( t=2.133, -2.286, χ2=10.250, P<0.05). There was no significant difference in the volume of intraoperative blood loss, length of distal margin from surgical specimen, or the number of lymph node dissected between the two groups ( Z=-0.662, -1.107, 0.304, P>0.05). There was also no significant difference in the positive rate of circumferential margin or positive rate of distal margin between the two groups ( P>0.05). (2) Postoperative recovery: the time to first anal flatus of the traditional approach group was 51 hours (range, 48-64 hours). There were 3 patients with complications in the traditional approach group. One patient in the traditional approach group had postoperative anastomotic fistula of Clavien-Dindo classification Ⅱ, and was cured after conservative treatment including sufficient drainage, parenteral nutrition and anti-infective treatment. One patient had chylous fistula of Clavien-Dindo classification Ⅱ, and was cured after conservative treatment. One patient had pulmonary infection of Clavien-Dindo classification Ⅳa, and was cured after treatment in ICU. The duration of postoperative hospital stay of the traditional approach group was (11.3±4.5)days. The time to first anal flatus of the mesocolon approach group was 59 hours (range, 49-70 hours). One patient in the mesocolon approach group had paralytic ileus of Clavien-Dindo classification Ⅰ, and was cured after conservative treatment. The duration of postoperative hospital stay of the mesocolon approach group was (9.6±1.8)days. There was no significant difference in the time to first anal flatus or duration of postoperative hospital stay between the two groups ( Z=-0.554, t=1.884, P>0.05). There was no significant difference in the complications between the two groups ( P>0.05). (3) Follow-up: 61 patients were followed up for 6-18 months, with a median time of 12 months. There was no local recurrence or metastasis of tumors in patients during the follow-up. Conclusion:The mesocolon approach is safe and feasible in TaTME, which abides by the principle of radical resection, and can decrease the difficulty of mesocolon excision, shorten the time of transabdominal operation, increase the length of proximal margin from tumor specimen, improve the integrity of mesentery.