Colon Cancer Poop: Everything You Should Know And What to Watch Out For

Colon cancer ranks second¹ in causing cancer-related deaths in men in the US and is the third most common cause of cancer-related deaths in women.

One reason behind this high mortality is the lack of symptoms in its early stages. As a result, many diagnoses occur when the malignancy has spread to other parts of the body.

With the median age of colorectal cancer diagnosis being 71 in women and 67 in men, it is easy to dismiss bowel problems as age-related instead of investigating cancer as the cause.

It is vital to understand and recognize the telltale signs so you can seek early treatment.

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General symptoms of colon cancer

The signs and symptoms to look out for include:

Early warning signs

  • Sudden weight loss

  • Narrow or ribbon-like stools

  • Rectal bleeding

  • Anemia

  • A feeling like you need to pass stools all the time even though the bowels are empty.

  • Unexplained weight loss

  • Persistent abdominal pain

Sometimes these symptoms may result from other conditions such as Crohn's disease, hemorrhoids, and ulcers. However, you should discuss the symptoms with your doctor as soon as they are noticed.

Local symptoms

Local symptoms have not spread to distant organs but only affect the colon.

They include:

  • Diarrhea

  • Constipation

  • Rectal bleeding

  • Alternating diarrhea and constipation

  • Abdominal bloating

  • Thin stools

If you experience these symptoms persistently, you should visit a healthcare professional for a checkup.

Systemic symptoms

These symptoms may affect the entire body. They include:

  • Nausea

  • Vomiting

  • Jaundice

  • Anemia

  • Fatigue

  • General body weakness

Colon cancer stool

Bleeding from the rectum is one of the symptoms of colorectal cancer. Stool appearance can be a good indicator of what is happening inside your body.

Although a small, hard stool could mean constipation, you should see your physician when you see any of the following changes in stool appearance:

Change in shape

Thin stools are a sign of colon cancer. Any time you notice a narrow or ribbon-like stool, it indicates changes in your colon.

The color

Brown: Diet and the amount of bile determine the color of your stool. Bile is yellow-green and helps digest fats. Therefore, a healthy stool should have all colors of food you eat together with bile. Almost any brown shade is okay.

Green: Although it might come as a shock, green poop may not be serious. It could be because you ate too many green vegetables or green food coloring.

It may mean that food is moving via your intestines too fast, and the green in the bile has no time to break down. However, you should see a healthcare professional if the green color persists.

Shades of red: Stools with shades of red can result from taking red-colored medicine, excess red food coloring, or eating beetroot. However, the stool should return to normal after a day or two.

On the other hand, a bright red stool may mean your intestines are bleeding. It could be blood from hemorrhoids, infection, inflammation, or cancer. Consult your doctor if you pass red stools regularly.

Black: Black stools could be due to taking over-the-counter medicines or iron supplements. However, you should check with your doctor if this does not apply to you. 

A black or dark maroon stool that looks tarry and smells bad may indicate that your upper digestive tract (e.g., stomach) is bleeding. You should seek urgent medical attention if you have black, tarry stools.

Changes in bowel habits

Changes in bowel habits occur in most people, but a physician should evaluate some changes if they persist.


Loose stools are a common occurrence and could be due to intolerance to medication, stress, certain foods, or an infection.

Most people may get mild diarrhea a few times in a year, a condition that resolves itself in two to three days. However, if diarrhea persists for more than three days, your physician should investigate.


Constipation is among the most common gastrointestinal complaints. Having this condition does not always mean you have colorectal cancer. It could be due to poor nutritional habits, lack of physical activity, stress, or dehydration.

However, if your constipation is persistent, you should seek medical intervention.


Colon cancer usually begins as a benign growth (polyp). Adenomas², a type of polyp, are benign growth of the tissue lining colon or rectum. Most of them stay benign, but some can turn into cancer over time. Early removal of adenomas can prevent them from turning into cancer.

There are several screening options, and each has its benefits and drawbacks. Your physician can advise on the appropriate options, and together you can choose the appropriate tests for you.

The tests involved include:


This involves using a tube with a camera attached to it to visualize the insides of your intestine. The process uses a long, slender, flexible tube with a tiny video camera to check your entire colon and rectum. If the doctor finds any suspicious areas, they can pass surgical tools via the tube to pick tissue samples for analysis and remove polyps.

Blood tests

A blood test cannot tell if you have colon cancer. However, your doctor may test your blood for more insights about your overall health, including liver and kidney function tests.

Once a cancer diagnosis has been established, the physician may test your blood for carcinoembryonic antigen³ (CEA), a substance produced by certain types of cancer cells, including colorectal cancer.

Monitoring the CEA level in the blood can help the doctor understand the patient's prognosis and response to treatment. You should note that CEA can be elevated in some non-malignant conditions, such as liver cirrhosis or cigarette smoking.

Determining the stage of the cancer

If you are diagnosed with colorectal cancer, the doctor may recommend tests to establish the stage of your cancer. Staging can help determine the most appropriate treatment for you.

These tests may include imaging, such as CT scans of the chest, abdomen, and pelvis. An MRI or a PET scan may also be helpful. 

Colon cancer treatment by stage

Stage 0

In stage 0, the colon cancer is localized to the inner lining of the colon. A doctor will perform surgery to remove the tumor only. It can be through polyp removal or local excision of the area with cancer.

Stage I

In stage I, the colon cancer may have extended into the innermost layers of the colon wall but is yet to spread outside the colon wall or into the adjacent lymph nodes. A more extensive surgical approach may be required if localized surgery isn’t adequate.

Stage II

In stage II, colon cancer may have further extended through the colon wall but is yet to spread to the lymph nodes. It may invade directly into adjacent tissue. Partial colectomy or surgery to remove the cancer-containing section and the adjacent lymph nodes is the recommended treatment.

Selected patients may require chemotherapy following surgery. Your doctor will advise you if this is required.

Stage III

Stage III colon cancers have spread to adjacent lymph nodes but are yet to reach other body parts. Partial removal of the colon and chemotherapy following surgery is the recommended treatment for this stage of cancer.

Following treatment, regular follow-ups are required to ensure that cancer does not come back.

Stage IV

Stage IV colon cancer has spread from the colon to distant tissues and organs. This cancer often spreads to the liver and can also spread to other organs such as the lungs and brain. Surgery is not likely to cure these cancers.

Surgery may be considered if the spread is minimal; however, generally, these cancers are not curable. Treatment consists of chemotherapy and biological agents.

The lowdown

It is important to seek medical attention if you have any concerning symptoms. Colon cancer is treatable when detected at an early stage.

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We make it easy for you to participate in a clinical trial for Colon cancer, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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