Signs of Colon Cancer

It is important for a person to recognize the signs of colon cancer early in the course of the disease so that prompt treatment is initiated. However, in many instances, there are no symptoms of colon cancer in the early stages or they are very non-specific. The signs of colon cancer are usually dependent on the site of the cancer.

Signs of Colon Cancer on Right Side

The bowel on the right side has a thicker lumen and is more spacious compared to the bowel on the left side. Therefore, bowel cancer of the right side grows to a large size before producing any noticeable symptoms. The most common sign of the right sided bowel cancer is:

  • Iron deficiency anemia: This symptom is a result of blood loss over a long period of time. Small amount of blood loss occurs from the tumor site, which gets mixed with the feces, and may be detected only on the chemical analysis of stools. This gradual loss of blood may lead to anemia which, in turn, may result in shortness of breath, weakness and lethargy. It is only when the tumor has grown to a big size that the loss of blood in stools is substantial leading to dark colored stools called as melena.

Signs of Colon Cancer on Left Side

The colon on the left side is narrower. Therefore, any abnormal growth on the left side may cause obstruction of the bowel. The signs on the left side include:

Change in bowel habits: The most noticeable signs of colon cancer of the left side include a distinct change in the bowel habits. The patient may experience days of constipation followed by bouts of diarrhea. The stools may become narrowed and string like, what in medical parlance is termed as “pencil stools.” The patient may complain of a sense of urgency or get a feeling of incomplete evacuation. There may be mucus in the stools.
Complete bowel obstruction: The cancer may grow so large that it may completely obstruct the bowel’s lumen. This may lead to severe pain in abdomen associated with vomiting.
Perforation: The cancer may erode the entire thickness of the bowel wall making a hole and causing a perforation. In such a scenario, the feces may leak into the abdominal cavity leading to symptoms of shock.
Rectal bleeding: A tumor in the lower part of the bowel or the rectum may bleed leading to blood tinged stools. In this case, the blood in the stools is often bright red in color and may be confused to be a symptom of hemorrhoids.
As the cancer increases in size, the patient may complain of other associated signs of colon cancer. The symptoms of bowel cancer in the late stage may include:

Severe pain in the lower abdomen.
A palpable lump in the lower abdomen.
Extreme fatigue.
Unexplained weight loss.
Bloating of the abdomen.
Heavy bleeding in the stools.
All the signs of the colon cancer in early stage like altered bowel habits, anemia, shortness of breath and weakness but much more exaggerated than before.

Other Signs of Colon Cancer


The symptoms of colon cancer are often confused with those of other diseases like irritable bowel syndrome, peptic ulcer disease, ulcerative colitis, Crohn’s disease and diverticulosis. Because of this confusion, valuable time is lost and the cancer is often diagnosed very late. It is important for the people to recognize the signs of colon cancer and they should meet their doctors as soon as they notice any of these signs. Although bowel cancer can strike at any age, people above the age of fifty are at a higher risk of developing this cancer. It has been noticed that while women are more likely to suffer from colon cancer, men are more predisposed to be afflicted by cancer of the rectum.

There are certain other factors which increase the likelihood of developing colorectal cancer. These include:

  • A family history of bowel cancer: The chances increase if either of the parents or any sibling has a history of colorectal cancer.
  • Personal history: Patients of breast, ovarian or uterine cancer are at an increased risk. A person who developed bowel cancer before the age of 60 is more likely to develop it a second time.
  • Diabetes: Patients suffering from diabetes have 30% to 40% more risk of developing this cancer.
  • History of adenomatous polyps: A patient with history of developing adenomatous polyps or a positive family history of familial adenomatous polyposis is at an increased risk of developing colon cancer.
  • Diet: People eating a diet poor in fibers are more likely to suffer from bowel cancer.

People who are at a higher risk of developing colon cancer are advised to go for regular colorectal screening tests. This is done to detect the disease at an early stage where it is easier to treat. These screening tests include colonoscopy, barium enema, sigmoidoscopy and CT colonography. Such people are also advised to go for regular fecal occult blood test to detect any blood loss in the stools. The importance of early recognition of the signs of colon cancer cannot be stressed enough.

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