What is the approach to dividing the rectum in a general adult population with rectal cancer?

Division of the Rectum in Rectal Cancer Surgery

For rectal cancer resection, the rectum should be divided using total mesorectal excision (TME) with a distal margin of at least 2 cm below the tumor, employing sharp dissection along anatomical planes to remove the mesorectum en bloc while preserving autonomic nerves. 1

Surgical Margin Requirements

The fundamental principle for dividing the rectum is achieving adequate oncological clearance:

• A minimum distal margin of ≥2 cm between the tumor and the rectal stump is mandatory for satisfactory tumor clearance 1, 2
• This measurement should be taken on the unfixed specimen 1
• For upper third tumors requiring anterior resection, a margin of at least 5 cm distally is recommended to avoid tumor cell spillage 1

Total Mesorectal Excision (TME) Technique

TME represents the gold standard approach for dividing the rectum in cancer surgery:

• En bloc removal of the mesorectum, including associated vascular and lymphatic structures, fatty tissue, and mesorectal fascia through sharp dissection 1
• The dissection should be performed in the appropriate anatomical plane between the mesorectal fascia and the parietal pelvic fascia 3
• Autonomic nerve preservation should be attempted during TME 1

Critical caveat: For tumors of the lower or middle third of the rectum that are palpable on digital examination, excision of the entire mesorectum is essential to reduce locoregional recurrence risk 1, 2, 4

Location-Specific Approaches

Upper Third Rectal Tumors

• Low anterior resection (LAR) extended 4-5 cm below the distal tumor edge using TME, followed by colorectal anastomosis 1
• Partial mesorectal excision (PME) with division 5 cm below the tumor may be acceptable for selected upper third tumors, though TME remains preferred 5

Middle Third Rectal Tumors

• Sphincter-preserving surgery (anterior resection or coloanal anastomosis) is usually possible 1
• TME with colorectal or coloanal anastomosis 1

Lower Third Rectal Tumors

• Abdominoperineal resection (APR) with TME is usually required when the tumor directly involves the anal sphincter or levator muscles 1
• Coloanal anastomosis may be considered in selected cases where sphincter function can be preserved 1
• When performing APR, epiplooplasty to fill the perineal wound is recommended 1, 4

Technical Considerations During Division

Avoid dividing the rectum at the middle pelvic level as this significantly increases the risk of pelvic nerve injury during subsequent procedures 2

When creating anastomoses:

• Negative margins (>3 mm) are required for both deep and mucosal margins 1
• For coloanal anastomoses, the maximum length of anorectal mucosa between the dentate line and anastomosis should not exceed 2 cm 2
• Construction of a colonic pouch to replace the rectal reservoir improves functional outcomes 1

Lymphadenectomy Requirements

• A minimum of 6-8 lymph nodes must be examined in the resected specimen 1
• Extension of nodal dissection beyond the field of resection (e.g., into iliac lymph node distribution) is not recommended unless nodes are clinically suspicious 1
• Wide TME facilitates adequate lymphadenectomy and improves the probability of achieving negative circumferential margins 1

Common Pitfalls to Avoid

• Inadequate mesorectal excision for lower third tumors leads to higher local recurrence rates 2, 4
• Attempting nerve-sparing procedures without ensuring adequate tumor clearance—procedures conserving erector nerves are not recommended as their adverse effect on local tumor control has not been excluded 1, 2
• Insufficient distal margin (<2 cm) compromises oncological outcomes 1, 2
• Dividing at the mid-rectal level creates technical difficulties and increases nerve injury risk 2

Quality Outcomes

When TME is performed correctly with adequate margins, local recurrence rates should be approximately 5-7% at 5 years 5. However, preoperative radiotherapy for T3-T4 tumors further reduces local recurrence 1. The emphasis must be on sharp dissection in the correct anatomical plane to achieve complete mesorectal excision while minimizing functional morbidity 1, 3.