Low Anterior Resection for Rectal Cancer
Low anterior resection is performed for cancer in the recto-sigmoidal junction (option d). This surgical approach is the treatment of choice for lesions in the mid to upper rectum, while lower rectal lesions may require abdominoperineal resection or coloanal anastomosis 1.
Anatomical Considerations for Surgical Decision-Making
- For tumors in the mid to upper rectum, a low anterior resection is the treatment of choice 1
- For lesions in the lower rectum, abdominoperineal resection or coloanal anastomosis is typically required 1
- Low anterior resection is appropriate for tumors located in the rectosigmoid junction, as these are in the upper portion of the rectum 1
- Tumors within 8 cm of the anal verge but limited to 30% of the rectal circumference may be candidates for transanal excision rather than low anterior resection 1
Contraindications for Low Anterior Resection
- Cancer starting from the dentate line and extending 8 cm proximally (option a) would typically require abdominoperineal resection due to its low location and extension 2
- Cancer 5 cm proximal to the dentate line (option b) may be too low for standard low anterior resection and might require ultralow anterior resection with coloanal anastomosis 3
- Cancer involving the internal anal sphincter fibers (option c) would contraindicate sphincter preservation and require abdominoperineal resection 2
- Cancer distal to the dentate line (option e) would require abdominoperineal resection as sphincter preservation is not possible 1, 2
Surgical Margins and Technical Considerations
- To obtain satisfactory tumor clearance, the safe margin between the lower end of the tumor and the rectal stump must be greater than or equal to 2 cm 1
- A minimum of 6-8 lymph nodes should be examined for proper staging 1
- For tumors of the lower third of the rectum, or the middle third but palpable by digital examination, excision of the entire mesorectum reduces the risk of locoregional recurrence 1
- Distal surgical margins should be at least 1 cm from the tumor in cases of differentiated cancer and localized tumors of stage T2 or less 2
- Margins greater than 2 cm are recommended in poorly differentiated cancer and tumors of stage T3 or greater with total mesorectal excision 2
Outcomes and Functional Results
- Low anterior resection for tumors in the rectosigmoid junction has better functional outcomes compared to ultralow anterior resection 3
- Patients with low rectal cancers undergoing ultralow anterior resection plus coloanal anastomosis often experience severe bowel dysfunction 3
- Risk factors for major Low Anterior Resection Syndrome (LARS) include advanced age (>70), male sex, ultralow anterior resection, and chemoradiation therapy 3
- For tumors within 8 cm of the anal verge, both low anterior resection and abdominoperineal resection achieve equivalent oncologic results measured by local recurrence rates and overall survival 4
Conclusion
The location of the tumor in the rectum is the primary determinant for the type of surgical approach. Low anterior resection is specifically indicated for tumors in the rectosigmoid junction (option d), as these are located in the upper portion of the rectum where sphincter preservation is feasible while maintaining adequate oncologic outcomes 1, 2.