Why is dividing the rectum at the middle level within the pelvis avoided?

Dividing the Middle Rectum Within the Pelvis: Surgical Risks and Considerations

Dividing the rectum at the middle level within the pelvis is not recommended because it significantly increases the risk of pelvic nerve injury during subsequent proctectomy procedures. 1

Anatomical and Surgical Considerations

• When performing subtotal colectomy with a rectal remnant, dividing at the middle rectum level creates technical difficulties during follow-up surgeries that can lead to increased morbidity 1
• The pelvic autonomic nerves are particularly vulnerable as they lie close to the anterior aspect of the rectum at the level of the prostate or upper vagina 2
• These nerves are buried in endopelvic fascia on the pelvic side wall but become more exposed and at risk during middle rectal dissection 2

Recommended Alternatives

Instead of dividing at the middle rectum level, surgeons should consider:

• Dividing the rectum at the level of the promontory (recto-sigmoid junction) 1
• Alternatively, leaving the distal part of the sigmoid colon in situ, which allows:
  • Better anchoring to the anterior abdominal wall 1
  • Easier subsequent identification and dissection 1
  • Possibility of relocation through abdominal fascia (either closed in subcutaneous fat or as a mucous fistula) 1

Management of the Rectal Remnant

When managing the rectal remnant after subtotal colectomy:

• Creating a mucous fistula is considered safe as no closed bowel is left within the abdomen, though it results in an additional stoma for the patient 1
• Closing the stump and leaving it within subcutaneous fat is also safe, but requires the skin to heal through secondary intention to avoid wound infection 1
• There are currently no definitive studies on the risk of subsequent inflammation or bleeding after leaving different lengths of rectum or recto-sigmoid colon in situ 1

Considerations for Restorative Proctocolectomy

For patients undergoing pouch surgery:

• The maximum length of anorectal mucosa between the dentate line and anastomosis should not exceed 2 cm 1
• A covering loop ileostomy is generally recommended when performing restorative proctocolectomy for ulcerative colitis 1
• A low-stapled anastomosis, when properly performed, provides better outcomes regarding soiling, fecal leakage, and social restriction 1

Surgical Approach for Rectal Cancer

For rectal cancer management:

• To obtain satisfactory tumor clearance, a safe margin between the lower end of the tumor and rectal stump must be ≥ 2 cm 1
• For tumors of the lower third of the rectum, or middle third but palpable by digital examination, excision of the entire mesorectum reduces the risk of locoregional recurrence 1
• Procedures attempting to conserve the erector nerves are not recommended as their effect on local tumor control has not been excluded 1

Complications and Risks of Improper Technique

Major complications that can be avoided with proper anatomical dissection include:

• Hemorrhage from presacral veins 2
• Perforation of the rectum 2
• Damage to pelvic autonomic nerves leading to urinary and sexual dysfunction 2
• Creation of a dead space after rectal extirpation, which can lead to bowel obstruction, perineal hernia, abscess, or hematoma 3

By following these guidelines and avoiding division at the middle rectal level, surgeons can minimize complications and improve patient outcomes in terms of morbidity, mortality, and quality of life.