TME (Total mesorectum excision) is the golden standard of radical resection for mid-low rectal cancer. However, the damage of pelvic autonomic nerve following with TME principle will lead to high incidence of urinary and sexual function disorder. PANP (pelvic autonomic nerve preservation) surgery played a role in decreasing incidence of urinary and sexual function disorder. However, 32%-44% patients still suffered from urinary and sexual function disorder when underwent open (O-PANP-TME) or laparoscopic PANP TME surgery (L-PANP-TME).

In the early stage of work, the investigators performed preservation of Denovilliers' fascia in L-PANP-TME to discuss the protection of urinary and sexual function of male mid-low rectal cancer patients. The results showed that preservation of Denovilliers' fascia in L-PANP-TME significantly decreased incidence of urinary and sexual function disorder. In order to further confirm the early work, the investigators design a randomized controlled clinical trial to compare differences in urinary and sexual function protection and long-term outcomes between preservation and excision of Denovilliers' fascia in L-PANP-TME.

Inclusion Criteria:

1. Age from over 20 to under 60 years;
2. Primary rectal adenocarcinoma confirmed pathologically by endoscopic biopsy;
3. Mid-low rectal cancer (distance from anal edge≤12cm);
4. cT1-3, N0-3, M0 at preoperative evaluation according to the AJCC Cancer Staging Manual Seventh Edition;
5. Expected curative resection through L-PANP;
6. Performance status of 0 or 1 on ECOG (Eastern Cooperative Oncology Group) scale;
7. ASA (American Society of Anesthesiology) score class I, II, or III;
8. Written informed consent;
9. Urinary and sexual function normal preoperatively

Exclusion Criteria:

1. Severe mental disorder;
2. History of previous pelvic surgery;
3. Enlarged or bulky regional lymph node diameter over 3cm by preoperative imaging;
4. History of other malignant disease within past five years;
5. History of unstable angina or myocardial infarction within past six months;
6. History of cerebrovascular accident within past six months;
7. History of continuous systematic administration of corticosteroids within one month;
8. Contraindication of heart, brain, lung, etc dysfunction;
9. Requirement of simultaneous surgery for other disease;
10. Emergency surgery due to complication (bleeding, obstruction or perforation) caused by rectal cancer;
11. Rectal cancer invades surrounding tissues;
12. Existence of genuine incontinence or severe stress incontinence preoperatively