What is the difference between Abdominoperineal Resection (APR) and Low Anterior Resection (LAR)?

Differences Between Abdominoperineal Resection and Low Anterior Resection

The key difference between Abdominoperineal Resection (APR) and Low Anterior Resection (LAR) is that APR involves complete removal of the rectum and anus with permanent colostomy creation, while LAR preserves the anal sphincter and allows for bowel continuity through a colorectal anastomosis. 1

Anatomical and Surgical Differences

• APR involves en bloc resection of the rectosigmoid, rectum, and anus, along with surrounding mesentery, mesorectum (TME), and perianal soft tissue, necessitating creation of a permanent colostomy 1
• LAR preserves the anal sphincter and involves resection of the affected rectum with TME, followed by creation of a colorectal or coloanal anastomosis, maintaining intestinal continuity 1
• For mid to upper rectal lesions, LAR extends 4-5 cm below the distal edge of the tumor using TME technique 1
• Both procedures incorporate total mesorectal excision (TME), which involves en bloc removal of the mesorectum with associated vascular and lymphatic structures 1

Indications for Each Procedure

• APR is indicated when:

  • The tumor directly involves the anal sphincter or levator muscles 1
  • A margin-negative resection would result in loss of anal sphincter function and incontinence 1
  • The tumor is located very low in the rectum with anal canal involvement 2

• LAR is indicated when:

  • The tumor is located in the mid to upper rectum 1
  • Anal function is intact and adequate distal clearance (4-5 cm below tumor edge) can be achieved 1
  • Sphincter preservation is possible without compromising oncologic outcomes 3

Oncological Outcomes

• Recent retrospective comparisons show that patients treated with APR have worse local control and overall survival compared to those treated with LAR 1, 4
• A meta-analysis of 13 studies (6,850 cases) demonstrated that LAR is highly correlated with better 5-year survival (pooled OR = 1.73) and lower local recurrence rates compared to APR 4
• APR is associated with higher rates of circumferential resection margin (CRM) involvement compared to LAR 4, 5
• A retrospective study of 3,633 patients with T3-T4 rectal cancer suggests an association between the APR procedure itself and increased risks of recurrence and death 1
• The CAO/ARO/AIO-04 trial showed that APR after preoperative chemoradiotherapy was associated with worse overall survival, disease-free survival, and higher local recurrence rates compared to LAR 6

Quality of Life Considerations

• In the NSABP R-04 trial, patients who underwent APR reported worse body image, worse micturition symptoms, and less sexual enjoyment at 1-year post-surgery compared to those who had sphincter-preserving surgery 1
• The CAO/ARO/AIO-04 trial found slightly poorer role functioning and physical functioning in APR patients after 3 years 6
• Despite these differences, overall quality of life between patients with or without a permanent colostomy appears to be fairly comparable in some studies 1

Technical Considerations

• An extralevator APR approach may offer benefits over conventional APR, including lower rates of intraoperative perforation, CRM involvement, and local recurrence, though results are inconsistent across studies 1
• For LAR with coloanal anastomosis, key technical points include complete mobilization of the left colon, sharp dissection, restoration of the anorectal angle, meticulous hemostasis, and often a temporary diverting colostomy 3
• Both procedures can be performed via open, laparoscopic, or robotic approaches with comparable oncological outcomes 1

Common Pitfalls and Caveats

• The poorer prognosis associated with APR may be partly explained by the inherent characteristics of lower rectal tumors rather than the procedure itself 6, 5
• Anterior tumor location, especially in women, more often requires downstaging and/or more extended resection to obtain free margins 5
• Quality of TME is significantly better and complete resection rates are higher in LAR compared to APR patients 6
• Intensified chemoradiotherapy may compensate for the higher risk of local recurrence after APR in patients with worse TME quality 6

When selecting between these procedures, tumor location, involvement of sphincter complex, potential for sphincter preservation, and patient factors must be carefully considered to optimize both oncological outcomes and quality of life 1.