Detailed chapter

Low Anterior Resection (LAR)

Sphincter-preserving rectal resection with TME and colorectal anastomosis — aiming for oncologic safety while keeping bowel emptying through the anus.

Low anterior resection (LAR) removes the rectum (and mesorectum with total mesorectal excision) for mid and selected low rectal cancers while preserving the sphincter mechanism, then joins colon to the remaining rectal stump (colorectal anastomosis). The goal is oncologic safety with continued defecation through the anus. Most low anastomoses are protected with a temporary ileostomy.

Low anterior resection — educational figure — Low anterior resection · educational illustration · English labels below

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TME plane

Who may be a candidate?

Mid-rectal and selected low-rectal tumors
No sphincter invasion on MRI / sphincter preservation feasible
Cases where an adequate distal margin can be achieved
Patients rendered suitable for sphincter-preserving surgery after neoadjuvant therapy / TNT

Possible advantages

Preserves anal sphincters and avoids permanent colostomy when oncologically safe
TME delivers the mesorectum as an intact package for local control
Open, laparoscopic, or robotic access can deliver LAR principles
Temporary ileostomy protects many low anastomoses and is later closed when healing is confirmed

Limits & realistic expectations

Tumors invading the anal sphincter usually need Miles (APR) instead
When a safe distal margin cannot be taken without sacrificing sphincters, LAR is not appropriate
Some patients prefer APR after counselling about low anterior resection syndrome (LARS) function
Low anastomoses carry leak risk and LARS (urgency, frequency, clustering)

Step-by-step overview

1
Exploration and colon mobilisation
Abdominal and pelvic assessment. Left colon and splenic flexure are freed so the anastomosis can reach without tension.
2
Vascular pedicle
IMA (and usually IMV) are ligated at oncologic levels. Lymph pathways are cleared with the mesentery; ureters and autonomic nerves are protected when possible.
3
Pelvic TME
Dissection in the mesorectal fascial plane from behind and sides, keeping the mesorectum intact as a cylindrical package. Anteriorly, care near prostate or vagina.
4
Distal transection
Rectum is divided below the tumor with an adequate safety margin (stapler or open technique). The margin must be pathologically negative.
5
Specimen removal
Tumor-bearing rectum and mesorectum come out intact. Proximal colon is prepared for join.
6
Colorectal anastomosis
Colon is joined to the rectal stump with circular stapler (double-staple / circular) or suture. Perfusion, tension, and air–water leak testing are checked.
7
Temporary stoma (most low LARs)
A loop ileostomy protects the anastomosis. Pelvic drain policy varies by centre and case.

Key points

LAR together with TME
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LAR is not merely ‘cutting the rectum.’ The mesorectum is removed intact (total mesorectal excision). Circumferential resection margin (CRM) and distal margin define oncologic quality.
Anastomosis height
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The lower the anastomosis, the higher the potential LARS burden (frequency, urgency, gas–stool discrimination). That trade-off is discussed before consent.
Temporary ileostomy
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Loop ileostomy is often used to reduce clinical impact of leak and protect healing. Weeks to months later, if the anastomosis is sound, it is closed.
High vs low anterior
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Upper rectal / rectosigmoid tumors may have a higher join (anterior / high anterior). ‘Low’ anterior means the anastomosis sits closer to the pelvic floor.
After surgery
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Early walking; pain and nausea control; ileostomy care teaching when applicable; leak vigilance (fever, tachycardia, pelvic pain, drainage); LARS education and pelvic-floor / diet support; stoma-closure timing; pathology ± adjuvant therapy.
- Early mobilisation
- Ileostomy education if diverted
- Leak warning signs
- LARS counselling and rehab
- Stoma closure after confirmed healing
Important
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Educational information only — MRI height, sphincter status, and response to neoadjuvant therapy decide LAR versus ultra-low or Miles with your surgical team.

Frequently asked questions

Will I have a permanent bag after LAR?
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The goal is no. Sphincters are preserved. Most patients have a temporary ileostomy that is later closed. Complications or oncologic necessity can change the plan.
How does LAR differ from Miles?
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In LAR the anal canal and sphincters stay and an anastomosis is made. In Miles the anal canal is removed and a permanent colostomy is created.
Can LAR be laparoscopic or robotic?
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Yes; selected cases can complete TME + LAR closed or robotically. Decision depends on anatomy, stage, and team experience.
When is the temporary ileostomy closed?
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After imaging or endoscopy confirms anastomotic healing, and after adjuvant therapy and overall fitness are reviewed. Timing is often months but individualized.
What is LARS and can it be treated?
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Low anterior resection syndrome includes frequent stools, urgency, fragmented emptying, and difficulty distinguishing gas from stool. Diet, medicines, pelvic-floor rehabilitation, and selected transanal irrigation can help.

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Educational information only; not a substitute for clinical evaluation.

Medical editor: Assoc. Prof. Cengiz Dibekoğlu, MD · Last medically reviewed: August 2026 · English patient-education chapter.