Colon Cancer & Your Poop: What to Watch For and When to Get Help

Changes in your bowel movements, such as blood in your stool, or looser and more frequent stools, can sometimes signal colon cancer. Abdominal pain is another common symptom.

It's important to remember that these changes don't always mean colon cancer; other gastrointestinal issues can cause similar symptoms. Also, some people with colon cancer might not show any symptoms at all and can have perfectly normal-looking stools [1].

This article will explain the link between colon cancer and your bowel movements, outline the specific signs to look out for, and advise you on when to seek medical help if you have concerns about colon cancer.

Colon Cancer and Poop: Early Warning Signs

One of the first clues of colon cancer can be a noticeable shift in your bowel movements or stool appearance. Stools linked to colon cancer might look thinner and vary from your usual in color and consistency.

Unexplained changes in your stool, especially if they worsen or continue, should raise more concern about colon cancer than almost any other symptom.

Here are some early indicators of colon cancer:

• Narrow, "Pencil" Stools: This can happen as a tumor grows, narrowing the passage in your intestines.

• Pain During Bowel Movements (Dyschezia): This symptom is often associated with rectal cancer.

• Feeling of Incomplete Bowel Emptying (Tenesmus): Commonly seen with early-stage rectal cancer.

• Rectal Bleeding: More frequent with rectal cancer or cancer in the lower bowel.

• Abdominal Pain: Occurs when local inflammation triggers pain receptors in your organs called visceral nociceptors.

• Fatigue: This can be due to intestinal bleeding, leading to a loss of red blood cells and the development of anemia [2].

Poop Changes in Regional Colon Cancer (Stage 3)

By stage three, colon cancer has spread to nearby lymph nodes. As the tumor grows deeper into the intestinal tissues and constricts the intestinal tract (known as the lumen), changes in bowel habits and stool tend to become more obvious.

The following additional symptoms often point to progressing colon cancer:

• Constipation: Partially due to increasing bowel obstruction.

• Diarrhea: Caused by intestinal fluid flowing around a partial blockage.

• Alternating Constipation and Diarrhea: This can be a more telling sign of colon cancer.

• Blood in Stool (Hematochezia): This can be bright red if the tumor is near the rectum, or dark red/maroon if it's higher up in the colon.

• Tenesmus: Can persist as colon cancer advances due to ongoing and increasing inflammation.

• Abdominal Bloating and Cramps: Partly because you can't pass gas when the bowel is obstructed.

• Symptoms of Iron Deficiency Anemia: This affects about 48% of people with colon cancer [3].

Eventually, scar tissue and strictures can lead to a partial or total bowel obstruction. Bleeding is typically more severe at this stage, even if it's not always clearly visible in the feces.

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Poop Changes in Advanced Colon Cancer (Stage 4)

Stage 4 colon cancer is defined by the spread of cancer to distant organs, a process called metastasis. At this most advanced stage, as intestinal blockage and bleeding worsen, symptoms can become more pronounced.

At this point, your poop might appear viscous and dark, often called melena. This is more commonly seen with right-sided malignancy and happens when oxygen and hemoglobin in the blood react during the blood's long journey to the rectum [6].

Other symptoms at this stage can include:

• Nausea and Vomiting: Usually occur when the obstruction becomes severe.

• Unexplained Weight Loss: A common result of advanced cancer, where widespread inflammation leads to muscle and weight loss, as well as a reduced appetite [7].

Sometimes, the overly strained tissues can rupture, leading to bowel perforation. Additional symptoms may also appear if the cancer spreads to common areas like the liver, lungs, or bones [8].

While symptoms are more common in stage 4 colon cancer, not everyone experiences them. In fact, many patients with metastatic colon cancer may be entirely symptom-free if there's no blockage, perforation, or bleeding [9].

In Summary

Colon cancer can cause changes in the color, content, and frequency of your bowel movements. These changes include blood in the stool, flat or narrow stools, diarrhea, and more frequent bowel movements. In later stages, poop can become thick and black.

Remember, other gastrointestinal issues can also cause these changes in bowel habits and stool consistency. However, you should always have these symptoms checked by a healthcare professional. Colon cancer is highly treatable if caught in its early stages.