Types and Causes of Bowel Cancer | Gastroenterology

Bowel Cancer

What is bowel cancer?

Bowel cancer is a general term for cancer that begins in the large intestine. Depending on where cancer begins, cancer of the intestine is sometimes called colon or rectal cancer. Bowel cancer is one of the most common kinds of cancer diagnosed in the UK. Most of the people diagnosed are over 60 years old.

Alternate name

  • Colorectal cancer
  • Colon cancer

Types of bowel cancer

Types of bowel cancer include:

  • Adenocarcinoma
  • Gastrointestinal stromal tumors (GIST)
  • Lymphoma
  • Carcinoids
  • Turcot condition
  • Peutz-Jeghers condition (PJS)
  • Familial colorectal cancer (FCC)

Causes of bowel cancer

Most cases of bowel cancer start as a type of polyp called an adenoma. These tumors are not cancerous, but they can turn into cancer.

In many cases, doctors do not know what causes tumors or what causes them to turn into cancer. However, there are genes that can change your risk of bowel cancer. These genes cause a small percentage of bowel cancers, but they knowingly increase the risk.

Hereditary conditions that increase your risk of bowel cancer include:

Familial adenomatous polyposis

People with familial adenomatous polyposis (FAP) develop hundreds to thousands of polyps in the colon and rectum. Polyps can begin to develop as early as adolescence and will become cancerous if they are not removed.

Lynch syndrome

Lynch syndrome increases the risk of bowel cancer, as well as tumors of the endometrium, ovary, gastric, urinary tract, brain, and pancreas. It is estimated that 3 percent of colon cancers are caused by Lynch syndrome.

People with Lynch syndrome often grow colon cancer earlier at age 50. They may have a family history of many people who had cancer, especially colon cancer. Lynch syndrome is caused by a dominant genetic mutation, which means that you only need to inherit the mutation from one parent to develop the condition.

MYH  associated polyposis

MYH – associated polyposis caused polyps in the colon and rectum, similar to the milder form of FAP. It is a dominant trait, which means that you must get a variation in the MYH gene from both parents to develop MYH – associated polyposis. Research on this condition is still in the early stages but suggests that it can significantly increase the risk of bowel cancer.

There is also a type of inherited colon cancer called hyperplastic polyposis syndrome. It causes hyperplastic polyps, which are generally benign, but also greatly increase the risk of colorectal cancer. Research is in the early stages, and at this time, there are no known genes associated with this syndrome.

Symptoms of bowel cancer

Bowel cancer may not have any symptoms, especially in the first steps. If you experience symptoms during the first steps, they may include:

  • Constipation
  • Diarrhea
  • Changes in stool color
  • Changes in stool shape, like pointy stools
  • Blood in the stool
  • Rectal bleeding
  • Unjustified gas
  • Abdominal cramps
  • Abdominal pain

Risk factors for bowel cancer

Diet: Foods high in fiber, including fruits, vegetables, and grains, can reduce the risk of bowel cancer. Many of these foods are also rich in B vitamins, which can also lower the risk of colorectal cancer.

Inactivity: Regular exercise after a bowel cancer diagnosis can also improve survival rates. It can also decrease the risk of recurrence.

Smoking: People who smoke have a higher risk of bowel cancer.

Age: bowel cancer is rare in people under 50 who do not have an associated genetic condition. The risk increases as you get older.

Weight: obesity is associated with an increased risk of bowel cancer, especially in men.

Chronic inflammatory conditions: People with chronic inflammatory conditions that affect their colons, such as Crohn’s disease and ulcerative colitis, may be at increased risk of colon cancer.

Diagnosis of bowel cancer

Fecal tests: You may have fecal tests every 1 to 2 years. Fecal tests are used to detect hidden blood in the stool. There are two main types, the guaiac-based fecal occult blood test and the fecal immunochemical test (FIT).

Fecal immunochemical test: The FIT observes hemoglobin, a protein saved in the blood. It is considered more accurate than the guaiac-based test.

This is because the FIT is supposed to detect upper gastrointestinal bleeding (a sort of bleeding that is rarely caused by bowel cancer). Also, the results of this test are not affected by food or medicine.

Blood test: Your doctor may do some blood tests to get a better idea of what is causing your symptoms. Liver function tests and completed blood counts can rule out other diseases.

Sigmoidoscopy: Minimally invasive sigmoidoscopy allows your doctor to examine the last section of your colon, known as the sigmoid colon, for abnormalities. The procedure, also known as flexible sigmoidoscopy, involves a flexible tube with a light on.

Colonoscopy: A colonoscopy involves the use of a long tube with a small camera attached. This procedure allows your doctor to look inside your colon and rectum to check for anything unusual. It is usually done after less invasive screening tests indicate that you may have bowel cancer.

During a colonoscopy, your doctor may also remove tissue from abnormal areas. These tissue samples can be sent to a laboratory for analysis.

Of the existing diagnostic methods, sigmoidoscopies and colonoscopies are the most effective in detecting benign growths that can turn into colorectal cancer.

Bone scan: Your doctor may order an X-ray with a radioactive contrast solution that contains the chemical element barium.

Your doctor inserts this liquid into your intestines by using a barium enema. Once in place, the barium result coats the covering of the colon. This helps improve the quality of X-ray images.

Computed tomography: CT scans give your doctor a detailed picture of your colon. A CT scan used to diagnose colorectal cancer is sometimes called a virtual colonoscopy.

Treatment options for bowel cancer


In the early stages of bowel cancer, your surgeon may surgically remove cancerous polyps. If the polyp has not been attached to the wall of the intestines, you probably have an excellent outlook.

If your cancer has outspread to the intestinal walls, your surgeon may need to take away a part of the colon or rectum along with connected lymph nodes. If possible, your surgeon will reattach the leftover healthy portion of the colon to the rectum.

If this is not possible, they can perform a colostomy. This involves creating an opening in the abdominal wall for waste removal. A colostomy can be temporary or permanent.


Chemotherapy affects the use of drugs to kill cancer cells. For people with colorectal cancer, chemotherapy is usually carried out after surgery, when it is used to kill persistent cancer cells. Chemotherapy also controls the growth of tumors.

Chemotherapy drugs used to treat colorectal cancer include:

  • Capecitabine (Xeloda)
  • Fluorouracil
  • Oxaliplatin (Eloxatin)
  • Irinotecan (Camptosar)

Chemotherapy often has side effects that must be controlled with additional medication.


Radiation uses a powerful beam of energy, similar to that used in x-rays, to attack and destroy cancer cells before and after surgery. Radiation therapy usually occurs along with chemotherapy.

Other medications

Targeted therapies and immunotherapies may also be recommended. Medications that have been approved by the Food and Drug Administration (FDA) to treat colorectal cancer include:

  • Bevacizumab (Avastin)
  • Ramucirumab (Cyramza)
  • Ziv-aflibercept (Zaltrap)
  • Cetuximab (Erbitux)
  • Panitumumab (Vectibix)
  • Regorafenib (Stivarga)
  • Pembrolizumab (Keytruda)
  • Nivolumab (Opdivo)
  • Ipilimumab (Yervoy)

They can treat late-stage or metastatic colorectal cancer that does not respond to other types of treatment and has spread to other parts of the body.


Certain risk factors for bowel cancer, such as family history and age, cannot be prevented.

However, lifestyle factors that can contribute to colorectal cancer are preventable and may help reduce your overall risk of developing this disease.

You can take steps now to condense your risk by:

  • Reduce the amount of red meat
  • Avoid processed meats, such as hot dogs and cold cuts.
  • Eat more plant-based foods
  • Reduce dietary fat
  • Exercise daily
  • Lose weight, if your doctor recommends it
  • Stop smoking
  • Reduce alcohol consumption
  • Reduce stress
  • Management of pre-existing diabetes

Another preventative measure is to make sure you have a colonoscopy or other cancer screening test after age 50. The earlier the cancer is found, the better the result.


There are some complications that can arise as a result of colon cancer.

Iron deficiency anemia: Due to microscopic bleeding from a tumor, iron deficiency anemia can occur as the first sign of colon cancer.7 Anemia is diagnosed with a blood test, called a complete blood count (CBC), and it can cause unusual tiredness symptoms. Dizziness, palpitations, and shortness of breath.

Bowel obstruction: A bowel obstruction from colon cancer means that the tumor is physically obstructed by the intestines. Depending on the severity of the blockage, solids, liquids, and even gases can be prevented from passing through the colon. This can lead to painful stomach cramps, bloating, and constipation, and sometimes nausea and/or vomiting.

While a nasogastric tube may be placed temporarily to reduce swelling and remove fluid and gas buildup from a bowel obstruction, surgery to remove the obstructing tumor or placement of a stent (to open the blocked area) is often required.

Jaundice – Another possible complication of colon cancer is jaundice, a condition in which the skin and whites of the eyes appear yellowish. Jaundice can occur when colon cancer spreads to the liver, a common site of metastasis. It can also occur due to the pressure of colon cancer on important structures related to the liver.

Departments to consult for this condition

  • Department of Gastroenterology

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