Colon Cancer: Signs, Symptoms, and Complications


As the second leading cause of cancer death in the United States, It is important to know the symptoms of colon cancer so that you can do everything you can to find it early, when it is most treatable. Some symptoms include cramps, abdominal pain, dark or bright red blood in the stool, or changes in stool frequency, such as persistent diarrhea or constipation. Whole-body symptoms, such as involuntary weight loss, loss of appetite, or unusual tiredness, can also occur in people with colon cancer.

Iron deficiency anemia and jaundice , which are complications of colon cancer, can also develop.

Research has shown that there is a significant delay between when people first notice the signs of colon cancer and when they are actually diagnosed. This lag time can lead to further spread of colon cancer, reducing the likelihood of successful treatment.

While it is true that most people with these symptoms do not get colon cancer, it cannot be assumed with certainty that this is the case.

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To better understand the symptoms of colon cancer, it helps to take a quick look at the anatomy of the colon .

The colon makes up most of the large intestine , which is about 6 feet long; the last 6 inches or so consist of the rectum and anal canal. Many people think that the small intestine is at the top and the large intestine at the bottom , but in reality they overlap and most of the colon is above the small intestine.

The ascending colon runs down the right side of the abdomen, the transverse colon runs horizontally through the upper abdomen, and the descending colon runs from the ribs on the left to the rectum and anus.

Frequent symptoms

In the early stages of colon cancer, symptoms are often absent. That's why regular screening tests starting at age 45 (and earlier for people with risk factors) are an important contribution to your health.

The symptoms below do not point directly to colon cancer in any way. In fact, they may indicate another problem in the gut, such as an infection (such as acute diverticulitis ), ulcers, or inflammation (such as Crohn 's disease). This is why it is so important to consult your doctor.

Colon cancer symptoms are of two main types: local symptoms (depending on the location of the tumor) and systemic symptoms (affecting the entire body).

Local symptoms

Symptoms of local colon cancer affect your bathing habits and the colon itself. These symptoms can include:

  • Changes in your bowel behavior: There is no universal 'normal' bowel movement. In fact, your healthcare provider only cares about what is normal for you. The size, color and consistency of each person's stool is unique. Therefore, it is important to notice any changes in your daily habits.
  • Abdominal discomfort: People with colon cancer may have abdominal pain or cramps.
  • Intermittent (alternating) constipation and diarrhea: Symptoms of alternating diarrhea and constipation can occur when the intestine is partially obstructed due to a tumor. Constipation can result from difficulty passing stool through an obstruction, followed by diarrhea, when the accumulated contents then escape.
  • Gas and Bloating: Excess gas and bloating can be a sign of colon cancer. However, diet triggers (such as soda, dairy, and high-fiber foods) and digestive disorders (such as inflammatory bowel disease ) are the common culprits.
  • Nausea and / or vomiting: When nausea and vomiting are symptoms of colon cancer, it is usually because the tumor is blocking the intestine.

If gas and bloating are associated with colon cancer, they are usually late symptoms caused by a tumor that is obstructing the colon. Swelling can also occur as a result of the cancer spreading to nearby lymph nodes.

If nausea and vomiting are accompanied by other warning signs, such as constipation, abdominal cramps, and / or bloating, colon cancer may be the cause.

Nausea and vomiting can occur at any stage of colon cancer, but are more common in the later stages of the disease. It is important to remember that nausea and vomiting without other symptoms of colon cancer are unlikely to be a sign of cancer.

The nature of the change in bowel movements can be described as follows:

  • Changes in the frequency of bowel movements: A persistent change (more than a few days) in the frequency of bowel movements is a potential sign of colon cancer. For example, if it is okay for you to have a bowel movement three times a day, but you only have one a day or once every other day, this could indicate constipation. On the other hand, if your typical pattern is to have a bowel movement every other day, and you have a bowel movement once a day, this may be unusually frequent and signal a change.
  • Stool reshaping: Thin or narrow stools, often described as tape or pencil-shaped stools, can also be a sign of colon cancer. In a healthy person, loose stools can be caused by a narrowing of the colon, also called a partial blockage of the colon due to colon cancer.
  • Changes in stool color: Bleeding in the colon due to colon cancer can result in bright red or dark red blood in the stool. In particular, if bleeding occurs in the ascending (right) colon, the stools may appear dark brown or purplish in color as the bleeding occurs further from the rectum. If the tumor is in the descending (left) colon, the bleeding tends to produce bright red stools (a discharge of fresh red blood is called hematochezia ).
  • Difficulty emptying stools – A persistent feeling that you need to empty your intestines, even if you just had one ( urgency ), can be a symptom of colon cancer.

Systemic symptoms

Symptoms of systemic colon cancer affect your entire body. These symptoms can include:

  • Unintentional Weight Loss – If you are losing weight effortlessly , this is a major symptom that should not be ignored. Colon cancer is just one of several serious conditions that can present initially with unexplained weight loss. The reason for unintentional weight loss in cancer is that tumors use the body's blood and nutrients to grow and grow. Also, some tumors release chemicals that increase the body's metabolism, which can lead to unexplained weight loss later on.

Unexplained weight loss is described as losing 10 pounds or more, or at least 5% of your body weight, over a period of six to 12 months. For example, if you weigh 150 pounds and have lost 7.5 pounds a year for no apparent reason, you should see your doctor.

  • Loss of appetite – An unusual loss of appetite is another sign to look out for. Although loss of appetite is more common with advanced cancers, it has been reported in some people with early colon cancer.
  • Unexplained fatigue: Extreme fatigue is a nonspecific symptom, but it is very common in people with advanced cancer. Cancer fatigue differs from "normal" fatigue in that it is generally not relieved by rest or neutralized by a good cup of coffee.
  • Feeling "withdrawn": It is not uncommon for people to feel that something is wrong with their body, even if they do not have specific symptoms to support this feeling. Trust your intuition. If you are concerned that something is wrong, make an appointment to speak with your healthcare provider.

Rare symptoms

If colon cancer is not diagnosed until it is advanced, it can cause one or more of the following symptoms:

  • Fever: If a tumor in the colon passes through the intestines, an abscess can form, causing a fever.
  • Air bubbles in the urine: Air bubbles in the urine (called pneumuria) can occur if a tumor in the colon invades the bladder.
  • Respiratory problems: If colon cancer has spread to the lungs, shortness of breath, coughing, and / or chest pain may occur.
  • Headache and neurological problems: If colon cancer spreads to the brain or spinal cord, headaches, vision changes, confusion, and / or seizures can occur.
  • Bone pain: Fractures, bone pain, and high calcium levels (found in a blood test) can occur if cancer spreads to the bones.


Colon cancer complications can include:

  • Iron deficiency anemia: Due to microscopic bleeding from the tumor, iron deficiency anemia can be the first sign of colon cancer. Anemia is diagnosed with a blood test called a complete blood count (CBC) and can cause symptoms of unusual tiredness, dizziness, palpitations, and shortness of breath.
  • Jaundice: Another possible complication of colon cancer is jaundice, a condition in which the skin and whites of the eyes turn yellow. Jaundice can occur when colon cancer spreads to the liver, a common site of metastasis. It may also be due to the pressure of colon cancer on important structures associated with the liver.
  • Intestinal obstruction: Intestinal obstruction due to colon cancer means that the tumor is physically blocking the intestines. Depending on the severity of the blockage, solid, liquid, or even gaseous materials may not pass through the colon. This can lead to painful stomach cramps, bloating, constipation, and sometimes nausea and / or vomiting.

Although a nasogastric tube may be temporarily placed to reduce swelling and remove accumulated fluid and gas when the intestine is blocked, surgery is often required to remove the occlusive tumor or place a stent (to open the blocked area).

When to contact a healthcare provider

While many people have heard that blood in your stool can be a sign of colon cancer, almost any change in your bowel behavior is worth evaluating. While you may be concerned about the possibility of colon cancer, early diagnosis offers you the best chance for successful treatment. More than likely, something completely different is happening, something less serious than cancer.

A Discussion Guide for Health Professionals on Colon Cancer Treatment

Get our printable guide to your next doctor's appointment to help you ask the right questions.

Frequently asked questions

  • Colon cancer is believed to be caused by specific genetic mutations that "turn off" tumor suppressor genes that regulate cell death and "turn on" oncogenes that promote cell growth and support cell life. Together, these mechanisms can lead to uncontrolled division of colon cells and tumor formation. Mutations can be inherited or acquired.

  • Certain risk factors are believed to play a role in acquired mutations in colon cancer, including:

    • Being overweight or obese.
    • Passive lifestyle
    • Eat a diet rich in red meat and meat products.
    • Of smoking
    • Moderate to heavy alcohol consumption
    • Inflammatory bowel disease (IBD)

  • Early colon cancer is often asymptomatic, especially if the tumor is higher in the colon. When symptoms first appear, they often include:

    • Persistent change in bowel habits, including diarrhea and constipation (often alternating).
    • Changes in the consistency of stool.
    • Rectal bleeding
    • Blood in the stool
    • Cramps, gas, or abdominal pain
    • Feeling that your intestines are not emptying even after moving ( rectal urge )

  • Because colon cancer can cause a narrowing of the intestinal tract, pencil-shaped loose stools are common. The swelling can also cause bleeding, resulting in stools that range from dark red or maroon to tarry black.

  • If your healthcare provider suspects that you may have colon cancer based on your symptoms and test results (including a fecal occult blood test ), a colonoscopy will be scheduled to look inside the colon. During the procedure , a biopsy of abnormal tissue or polyps will be taken and sent to a laboratory for evaluation.

  • Colon cancer usually forms from a collection of benign cells called an adenomatous polyp . Although most of these polyps do not turn cancerous (cancerous), some of them can gradually turn into cancer over 10 to 15 years. Other types of colon cancer are more aggressive and can progress faster.

  • Colon cancer is the fourth most common cancer and the second leading cause of cancer death in the United States. Approximately 150,000 people develop colon cancer each year and more than 50,000 die from the disease.

  • Unlike some cancers, there are steps you can take to lower your risk of colon cancer, including:

    • Limit your consumption of red meat and meat products.
    • Avoid frying, baking or deep frying meat at high temperatures that create carcinogens .
    • Losing weight while being overweight or obese
    • Limit alcohol intake
    • Cigarette rejection

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