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What Is Low Anterior Resection?

Low anterior resection is colorectal surgery that removes a diseased portion of the rectum while preserving the anus and anal sphincter. The remaining colon is connected to the lower rectum or anal canal so bowel movements can continue through the natural route. The procedure is commonly used for mid or low rectal cancer when sphincter preservation is oncologically and functionally appropriate. Total mesorectal excision is often incorporated when the operation is performed for rectal cancer.

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What Is Low Anterior Resection?

Low anterior resection is colorectal surgery that removes a diseased portion of the rectum while preserving the anus and anal sphincter. The remaining colon is connected to the lower rectum or anal canal so bowel movements can continue through the natural route. The procedure is commonly used for mid or low rectal cancer when sphincter preservation is oncologically and functionally appropriate. Total mesorectal excision is often incorporated when the operation is performed for rectal cancer.

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Why Is Low Anterior Resection Performed?

The procedure is most commonly performed for rectal cancer that can be removed without sacrificing the anal sphincter complex. It can also be used for selected benign rectal diseases that require segmental removal. Tumor location, stage, response to preoperative therapy, sphincter function, pelvic anatomy, and the ability to create a safe anastomosis influence whether low anterior resection is suitable. Very low tumors involving the sphincters can require abdominoperineal resection instead.

How Is Low Anterior Resection Performed?

The surgeon mobilizes the sigmoid colon and rectum through an open, laparoscopic, or robotic approach and removes the diseased rectal segment. For cancer surgery, the mesorectum is dissected according to the required oncologic plane. The remaining colon is then connected to the lower rectum or anal canal with a stapled or hand-sewn anastomosis. A temporary diverting loop ileostomy is commonly added when the connection is very low or considered at increased risk for leakage.

What Is Recovery Like After Low Anterior Resection?

Patients are monitored for bowel function, pain, infection, urinary problems, hydration, and anastomotic healing after surgery. A temporary ileostomy, when used, remains in place until the bowel connection has healed sufficiently for reversal. Bowel frequency, urgency, clustering, incomplete emptying, and continence can change after low rectal surgery. These symptoms can improve over time, but some patients develop persistent low anterior resection syndrome and need dietary, medication, pelvic-floor, or other treatment.

What Are the Risks and Complications?

Possible complications include bleeding, infection, bowel obstruction, blood clots, urinary problems, and injury to nearby pelvic structures. Anastomotic leakage is a major concern because leakage can cause pelvic infection, sepsis, or the need for drainage, diversion, or reoperation. Pelvic nerve injury can affect bladder and sexual function. Long-term complications can include anastomotic stricture, chronic bowel dysfunction, fecal urgency, clustering, and incontinence.

Frequently Asked Questions About Low Anterior Resection

Does low anterior resection preserve the anus?

Yes. The operation is designed to preserve the anus and sphincter when the disease can be removed safely and a functional bowel connection can be created.

Is a temporary ileostomy always needed after low anterior resection?

No. A diverting ileostomy is commonly used for very low or higher-risk anastomoses, but the need depends on the operation, healing risk, and surgeon's judgment.

What is low anterior resection syndrome?

Low anterior resection syndrome is a group of bowel-function changes that can include urgency, frequent stools, clustering, incomplete emptying, and problems with continence.

Can a low anterior resection become permanent colostomy surgery?

The intent is sphincter preservation, but severe complications, anastomotic failure, recurrent cancer, or poor bowel function can occasionally lead to a permanent stoma later.

References

Low Anterior Resection: Surgery, Recovery & Outlook. Cleveland Clinic. https://my.clevelandclinic.org/health/procedures/low-anterior-resection. Date Accessed August 13, 2026.

Rectal cancer surgery. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/rectal-cancer-surgery/about/pac-20587354. Date Accessed August 13, 2026.

Low Anterior Resection Syndrome: What It Is & Treatment. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/low-anterior-resection-syndrome. Date Accessed August 13, 2026.

Does a stoma reduce the risk of anastomotic leak and need for re-operation following low anterior resection for rectal cancer: systematic review and meta-analysis of randomized controlled trials. PubMed Central (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC6465490/. Date Accessed August 13, 2026.

Management of anastomotic leak after elective anterior resection for rectal cancer. PubMed Central (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC12690630/. Date Accessed August 13, 2026.