Symptoms of Colon Cancer

As the second leading cause of cancer-related deaths in the United States, it's important to know the symptoms of colon cancer so you can do your best to catch it early, when it's most treatable. Some symptoms include cramping, belly pain, dark or bright red blood in your stool, or a change in your stool frequency, like persistent diarrhea or constipation. Whole-body symptoms, such as unintentional weight loss, loss of appetite, or unusual tiredness, may also occur in those 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 signs of colon cancer and when it is actually diagnosed. This lag time could result in colon cancer spreading further, which lowers the chance of successful treatment. 

While it's true that most people with these symptoms do not have colon cancer, it's never safe to assume that's the case.

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Anatomy

To better understand colon cancer symptoms, it helps to briefly review the anatomy of the colon.

The colon makes up most of the large intestine, which is approximately 6 feet in length; the last 6 inches or so are made up of the rectum and anal canal. Many people think of the small intestine as being on top and the large intestine as being down below, but there is actually overlap, and much of the large intestine lies above the small intestine.

The ascending colon travels up the right side of your abdomen, the transverse colon travels horizontally across your upper abdomen, and the descending colon travels from just under your ribs on the left, down to the rectum and anus.

Frequent Symptoms 

In the early stages of colon cancer, people often have no symptoms. This is why regular screening beginning at age 45 (and earlier for those with risk factors) is an important investment in your health.

The symptoms mentioned below by no means point directly to colon cancer. In fact, they could indicate another problem in the bowels, such as an infection (for example, acute diverticulitis), ulcers, or inflammation (for example, Crohn's disease). This is why seeing your healthcare provider is critical.

Colon cancer symptoms come in two general varieties: local symptoms (based on where the tumor is located) and systemic symptoms (involving the whole body).

Local Symptoms

Local colon cancer symptoms affect your bathroom habits and the colon itself. These symptoms can include:

  • Changes in your bowel habits: There is no such thing as a universally "normal" bowel movement. In fact, your healthcare provider really only cares about what is normal for you. The size, color, and consistency of everyone's stools are unique. Therefore, it is important to notice any change in your normal patterns.
  • Abdominal discomfort: Abdominal pain or cramping may occur in those who have colon cancer. 
  • Intermittent (alternating) constipation and diarrhea: Symptoms of alternating diarrhea and constipation may occur when there is a partial obstruction in the bowel due to a tumor. Constipation may occur due to difficulty in stool passing the obstruction, followed by diarrhea when backed-up contents are then passed.
  • Gas and bloating: Excessive gas and bloating can be a sign of colon cancer. However, dietary triggers (for example, carbonated beverages, dairy products, and high-fiber foods) and digestive disorders (for example, inflammatory bowel disease) are common culprits.
  • Nausea and/or vomiting: When nausea and vomiting are symptoms of colon cancer, it's usually because a tumor is causing a bowel obstruction.

If gas and bloating are related to colon cancer, they tend to be late symptoms caused by an obstructing tumor in the colon. Bloating may also occur as a result of cancer spreading to nearby lymph nodes. 

If nausea and vomiting are accompanied by other worrisome signs—such as constipation, abdominal cramping, and/or abdominal distension—colon cancer could be a cause. 

Nausea and vomiting may occur at any stage of colon cancer but are more common with advanced disease. It's important to remember that the occurrence of nausea and vomiting alone, without other colon cancer symptoms, is not likely an indication of cancer.

The nature of a bowel movement change can be described in the following ways:

  • Change in stool frequency: A persistent change (more than a few days) in stool frequency is one potential sign of colon cancer. For example, if it is normal for you to have three bowel movements per day, and you are having only one per day, or one every other day, this may signal constipation. On the other hand, if your typical pattern is to have a bowel movement every other day and you're having one bowel movement per day, it may be unusually frequent and could signal a change.
  • Change in stool shape: Thin or narrow stools, often described as ribbon- or pencil-like, may also be a sign of colon cancer. In an otherwise healthy person, thin stools may 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 may result in bright red or dark red blood in the stools. More specifically, if bleeding is in the ascending (right-side) colon, the stools may be more maroon or purple in color since the bleeding is occurring farther away from the rectum. If the tumor is in the descending (left-side) colon, the bleeding tends to result in bright red stools (the passage of fresh, red blood is called hematochezia).
  • Difficulty with stool evacuation: A persistent feeling that you need to have a bowel movement, even when you just had one (called tenesmus), may be a symptom of colon cancer. 

Systemic Symptoms

Systemic colon cancer symptoms are those that affect your whole body. These symptoms may include:

  • Unintentional weight loss: If you lose weight without trying, it is an important symptom that shouldn't be ignored. Colon cancer is only one of several serious conditions that might first present themselves with unexplained weight loss. The basis behind unintentional weight loss with cancer is that tumors use the body's blood and nutrients to thrive and grow. In addition, some tumors release chemicals that increase the body's metabolism, which can further lead to unexplained weight loss. 

Unexplained weight loss is described as losing 10 or more pounds or at least 5% of your body weight over a six- to 12-month period. For example, if you are a 150-pound person who lost 7.5 pounds in a year for no apparent reason, you should contact your healthcare provider.

  • Loss of appetite: Unusual loss of appetite is another sign to look out for. While the loss of appetite most often occurs with advanced cancers, it has been noted in some people with early colon cancer.
  • Unexplained fatigue: Extreme tiredness is a nonspecific symptom, but is very common in people with more advanced cancers. Cancer fatigue differs from "ordinary" fatigue in that it's not usually relieved by rest or counteracted by a good cup of coffee.
  • Feeling "off": It's not uncommon for people to have a sense that something is amiss in their body, even if they don't have specific symptoms to back up that feeling. Trust your intuition. If you are concerned that something is wrong, make an appointment to talk with your healthcare provider.

Rare Symptoms

If colon cancer is not diagnosed until its advanced stages, it may cause one or more of these symptoms:

  • Fever: If a tumor in the colon breaks through the intestines, an abscess may form, which causes a fever.
  • Air bubbles in urine: Air bubbles in your urine (called pneumaturia) may occur if a tumor in the colon invades into the bladder.
  • Problems breathing: If the colon cancer has spread to the lungs, shortness of breath, coughing, and/or chest pain may occur.
  • Headache and neurological problems: If the colon cancer spreads to the brain or spinal cord, headache, vision changes, confusion, and/or seizures may occur.
  • Bone pain: Fractures, bone pain, and high calcium levels (seen on a blood test) may occur if cancer spreads to the bones.

Complications

Complications of colon cancer may include:

  • Iron deficiency anemia: Due to microscopic bleeding from a tumor, iron deficiency anemia may occur as the first sign of colon cancer. Anemia is diagnosed with a blood test, called a complete blood count (CBC), and may cause symptoms of unusual tiredness, dizziness, palpitations, and shortness of breath.
  • Jaundice: Another potential complication of colon cancer is jaundice, a condition in which the skin and whites of the eyes take on a yellowish appearance. Jaundice may occur when colon cancer spreads to the liver, a common site of metastasis. It may also occur due to pressure from a colon cancer on important structures related to the liver.
  • Bowel obstruction: A bowel obstruction from colon cancer means that the tumor is physically blocking the intestines. Depending on the severity of the blockage, solids, liquids, and even gas may be prevented from passing through the colon. This can lead to painful stomach cramps, bloating, constipation, and sometimes nausea and/or vomiting.

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

When to See a Healthcare Provider

While many people have heard that having blood in their stools may be a sign of colon cancer, just about any change in your bowel habits is worth evaluating. While you may be anxious about the possibility of having colon cancer, early diagnosis offers you the best opportunity for successful treatment. There is a possibility that something else entirely is going on—something less serious than cancer.

Frequently Asked Questions

What causes colon cancer?

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 keep cells alive. These mechanisms together can cause cells in the colon to divide out of control and form tumors. The mutations may be inherited or acquired.

What are the risk factors for colon cancer?

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

  • Being overweight or obese
  • Living a sedentary lifestyle
  • Eating a diet high in red meats and processed meats
  • Smoking
  • Moderate to heavy alcohol use
  • Having inflammatory bowel disease (IBD)

What are the early signs of colon cancer?

Colon cancer is often asymptomatic in the early stage, especially if the tumor is higher up in the colon. When early symptoms do develop, they often include:

  • A persistent change in bowel habits, including diarrhea and constipation (often alternating)
  • Changes in stool consistency
  • Rectal bleeding
  • Blood in stools
  • Abdominal cramps, gas, or pain
  • A feeling that your bowels aren't empty even after a movement (rectal tenesmus)

What do stools look like if you have colon cancer?

Because colon cancer can cause the narrowing of the intestinal tract, thin, pencil-like stools are common. The tumor can also cause bleeding, leading to stools that range in color from a dark red or maroon to a tar-like black.

How is colon cancer diagnosed?

If your healthcare provider suspects you may have colon cancer based on symptoms and tests results (including the fecal occult blood test), a colonoscopy will be ordered to look inside the colon. During the procedure, a biopsy of abnormal polyps or tissues will be obtained and sent to the lab for evaluation.

How fast does colon cancer grow?

Colon cancer usually forms from a cluster of benign cells called an adenomatous polyp. While most of these polyps won't become malignant (cancerous), some can slowly turn into cancer within 10 to 15 years. Other types of colon cancer are more aggressive and may progress more rapidly.

How common is colon cancer?

Colon cancer is the fourth most common cancer and the second leading cause of cancer-related deaths in the United States. Nearly 150,000 people get colon cancer each year, while over 50,000 die of the disease annually.

Can you prevent colon cancer?

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

  • Limiting your intake of red meat and processed meats
  • Avoiding high-temperature frying, broiling, or grilling of meat, which creates carcinogens
  • Losing weight if overweight or obese
  • Limiting your alcohol intake
  • Quitting cigarettes

Colon Cancer Healthcare Provider Discussion Guide

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

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Article Sources
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