BMI ≥ 25 increased the operating time compared with BMI < 25 (p = 0.001); tumor size > 4 cm augmented the operating time compared with that ≤ 4 cm với (p = 0.005), tumors lying at the second third and the end of rectum had longer operating time than the first third (p = 0.05), ileum opening was done in the second and the third 1/3 compared with the first one third (p <0.05).