Low anterior resection (LAR) surgery treats colorectal cancer. Sometimes, the surgery is elective. Other times, it is an emergency procedure surgeons may perform for advanced-stage cancer.

Surgeons may perform low anterior resection (LAR) surgery to treat colorectal cancer. It involves removing the cancerous part of the rectum.

This article explores LAR surgery, including what the procedure involves. It also looks at what to expect before, during, and after surgery as well as surgery preparation, recovery, and risks.

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Before undergoing LAR surgery, a clinician will put a person to sleep using general anesthesia.

During LAR surgery, surgeons remove the cancerous portion of a person’s rectum. Additionally, they may also remove some healthy noncancerous tissue and lymph nodes in the surrounding area. The surgical team will then connect the colon to the remaining rectum.

LAR surgery typically takes around 4 hours for surgeons to perform.

Options for LAR surgery include:

Open surgery

During open surgery, surgeons make a single long incision in the abdomen, through which they remove the cancerous tissue.

Minimally invasive surgery

During a minimally invasive LAR procedure, surgeons make several small incisions in the abdomen. They then insert a video camera and small surgical instruments into the openings to remove the cancer. Surgeons may use a robotic device for assistance.

LAR surgery specifically treats colorectal cancers, including stage I, II, and III rectal cancers.

A 2019 study compared the success rates and complications of elective and emergency LAR surgery in 80 people. Results suggest that emergency LAR surgery may limit a surgeon’s ability to remove the cancer and preserve tissue.

The same study also showed that those who received emergency LAR surgery were more likely to experience postoperative complications than those who underwent planned surgeries.

However, the authors note that a long-term reevaluation of participants may be needed to fully understand the implications of emergency surgical interventions compared with scheduled surgery. This would include assessing:

  • long-term survival rates
  • quality of life
  • rates of other surgical complications, such as genital and urinary tract issues

Before undergoing LAR surgery, a person should let their surgical team know whether they:

  • are taking any medications, such as blood thinners
  • smoke
  • drink alcohol
  • experience sleep apnea

These factors may affect surgery and increase the likelihood of complications.

Around 30 days before surgery, a person’s medical team may recommend certain preparation steps, such as:

  • undergoing pre-surgical testing
  • meeting with a nurse practitioner (NP) for tests such as:
    • electrocardiogram
    • X-rays
    • blood tests
  • meeting with a wound, ostomy, and continence (WOC) nurse
  • identifying a caregiver
  • filling out a healthcare proxy form

Not everyone undergoing LAR surgery will have the same preparation. A person should always follow all recommendations and guidance their healthcare professional provides.

Immediately after surgery, most people will wake in the post-anesthesia care unit of the hospital. Here, a healthcare professional will monitor a person’s:

  • blood pressure
  • oxygen levels
  • temperature
  • heart rate

A person will also have a catheter and one or two drains in their lower abdomen.

If necessary, a person may receive oxygen through a mask or a tube inserted into the nose to help them breathe. They may also receive pain medications.

Most people will spend a few days in the hospital following LAR surgery. The length of the stay will depend on the type of surgery, how the surgery went, and the person’s overall health. By this point, any incisions may have already begun to heal.

Possible risks of LAR surgery include:

Recovery from LAR surgery will depend on the person and their treatment regime before surgery.

Certain people may be more likely to receive a temporary ileostomy. These include people who received chemotherapy, radiation therapy, or both as part of their treatment plan before surgery.

An ileostomy is when surgeons connect the final section of the small intestine, or the ileum, to an opening in the skin of the abdomen. This opening allows a person to pass stool while the rectum heals from surgery.

After about 8 weeks, surgeons can reverse the ileostomy procedure. A WOC nurse can show a person how to care for their ileostomy.

Following LAR surgery, a person may also need to:

  • follow a BRAT diet to control frequent bowel movements
  • regularly clean and dress their incision wounds
  • stay hydrated
  • avoid strenuous exercise and activity

For most people, recovery at home takes about 3–6 weeks.

The following are some questions people frequently ask about LAR.

What is the difference between LAR and APR?

An abdominoperineal resection (APR) is when surgeons remove the anus, rectum, and a portion of the sigmoid colon. They then insert a stoma through an opening in the abdomen.

APR is more invasive than LAR and results in a comparably lower quality of life.

What is the difference between high and low anterior resection?

A high anterior resection is similar to LAR. Surgeons make a higher incision to remove part of the left side of the colon, upper rectum, and surrounding lymph nodes.

Is low anterior resection a major surgery?

Yes. It is a major surgery requiring weeks of recovery.

Low anterior resection (LAR) surgery is when surgeons remove part of the colon and rectum to treat colorectal cancer.

It can take 3–6 weeks to recover from this major surgery. It may take up to 8 weeks before surgeons can reverse an ileostomy and a person can resume regular bowel movements.