Colorectal cancer

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Side effects of surgery for colorectal cancer

Side effects can happen with any type of treatment for colorectal cancer, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

Side effects can develop any time during, immediately after or a few days or weeks after surgery. Sometimes late side effects develop months or years after surgery. Most side effects will go away on their own or can be treated, but some may last a long time or become permanent.

Side effects of surgery will depend mainly on:

  • the type of surgery and amount of bowel removed
  • your overall health
  • the effect of other treatments – for example, tissue treated with radiation may not heal well after surgery

Tell your healthcare team if you have these side effects or others you think might be from your surgery. The sooner they are aware of any problems, the sooner they can suggest ways to help you deal with them.


Pain often occurs because surgery damages tissues. Surgery for colorectal cancer is a major operation, so it may take time for pain to go away after surgery. The intensity of the pain depends on the type of surgery, how you heal and how well you tolerate pain.

The healthcare team will prescribe drugs to control pain. Tell them if pain doesn’t go away or pain medicines don’t relieve the pain.

Find out more about pain.

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Bleeding, or hemorrhage, can occur if a blood vessel is not sealed off during surgery or if you have a blood-clotting disorder. Nursing staff frequently check bandages and drains for heavy bleeding right after surgery. If bleeding occurs and is severe enough, you may have to go back to the operating room so your surgeon can find where the bleeding is coming from and stop it.

A small amount of bloody drainage may be expected after surgery. Report heavy bleeding to your doctor or healthcare team.

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Blood clots

A blood clot in the leg is called deep vein thrombosis (DVT). DVT can occur right after surgery because you cannot move around very well, along with other factors. The signs and symptoms of a blood clot in the leg are a swollen, painful and red calf.

In the most serious cases, a blood clot can break off and travel to the lungs (called a pulmonary embolus, or PE). This can cause shortness of breath and low oxygen levels.

Changing position often, doing leg and ankle exercises and getting up and moving around as soon as possible can help reduce blood clots. People who have a high risk of developing blood clots may be given low doses of a blood thinner, such as heparin, to help prevent blood clots from forming.

Tell your healthcare team if you have any redness, swelling, pain or cramps in the calf of the leg, shortness of breath or coughing up blood.

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Diarrhea and constipation

Diarrhea and constipation often occur after surgery for colorectal cancer. Diarrhea is an increase in the number and looseness of stools. Constipation occurs when stools become hard, dry and difficult to pass. Sometimes constipation and diarrhea alternate. These problems often happen when a large part of the colon is removed. They can last a long time, but usually go away once you heal from the surgery. The healthcare team may give you antidiarrhea medicines.

Find out more about diarrhea and constipation.

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Paralytic ileus

Paralytic ileus is when the intestine becomes paralyzed or inactive so the contents cannot move through it. It commonly occurs after major abdominal surgery. It can also be caused by general anesthetic.

To prevent paralytic ileus, the surgeon can pass a nasogastric tube through the nose, down the esophagus and into the stomach during surgery. This tube will suck fluid and air out of the stomach. While it is in place, the person will be given intravenous fluid and will not be able to take food by mouth.

Paralytic ileus is a temporary problem that usually gets better a few days after surgery. The healthcare team will regularly check your bowel activity after surgery. You will gradually start taking fluids and foods by mouth (orally). The nasogastric tube is removed once you can eat and drink normally again.

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Abdominal adhesions

Abdominal adhesions are pieces of scar, or fibrous, tissue that make organs and tissues stick together. They often happen in people who have had colorectal cancer surgery. Adhesions do not usually cause symptoms, but they may cause pain in some people.

Adhesions can block the intestine (called bowel obstruction). If this happens, you may need more surgery to treat the bowel obstruction. Find out more about bowel obstruction.

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Damage to nearby organs

Sometimes nearby organs, including the small intestine, spleen, bladder or ureters, can be damaged during surgery to treat colorectal cancer. The surgeon may repair the damage during the same surgery, or you may need more surgery to fix it.

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Anastomotic leak

An anastomosis is the area where the 2 ends of the digestive tract are joined together. In rare cases, the stitches (also called sutures) or staples holding the 2 ends together may break or come apart. When this happens, the fluids inside the digestive tract leak into the abdomen. This is called anastomotic leak. It can cause inflammation of the peritoneum (the lining of the abdomen and abdominal organs). Symptoms of anastomotic leak include chills, fever and abdominal pain.

If you have an anastomotic leak, you may need to have more surgery to repair it. The healthcare team will also give you antibiotics.

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After surgery for colorectal cancer, some people develop an infection in the wound or where the 2 ends of the colon are joined together (called anastomosis). Infection is not a common side effect, but it can happen after any type of surgery. Sometimes your doctor will place tubes into the wound to drain extra fluid. Your doctor may also prescribe antibiotics to help prevent or treat an infection.

Wound infections are usually a temporary side effect of surgery. Tell your healthcare team if you have signs of infection, such as redness, pus or foul-smelling drainage, fever or increased swelling or tenderness of the incision site.

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Sexual problems

Some surgeries used to treat colorectal cancer can lead to sexual problems for men or women.

An abdominoperineal resection and low anterior resection can damage nerves in the pelvis. This damage can lead to erectile dysfunction, which is the inability to have or keep an erection. It can also lead to ejaculation problems, including retrograde ejaculation (semen goes into the bladder instead of the penis) and dry orgasm (no semen is ejaculated).

Women may have pain and discomfort during sex if scar tissue or adhesions develop in the abdomen.

Find out more about sexual problems for men and sexual problems for women.

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Changes to self-esteem and body image

Self-esteem is how you feel about yourself. Your body image is how you feel about your body. Having a colostomy or ileostomy can make some people feel uncomfortable with their bodies and affect their self-esteem.

Talk to your healthcare team. They can tell you about health professionals and groups that support people with ostomies and help them cope with changes to body image.

Find out more about self-esteem and body image and living with an ostomy.

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Bladder problems

Bladder problems may happen when surgery is done on the lower part of the large intestine, especially the rectum. Surgery can damage muscles or nerves connected to the bladder. The damage can cause symptoms like urinary incontinence, the need to urinate often and the intense need to urinate.

Your healthcare team may prescribe medicines to manage bladder problems.

Find out more about urinary incontinence.

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