10 Symptoms of Colon Cancer

Colon cancer is the presence of cancerous tumors in the colon or rectum. The third most commonly occurring form of cancer in the world, it usually begins with small, precancerous polyps, which may turn cancerous if they remain unchecked. Screening colonoscopies can help detect these polyps before they become malignant. Full recovery from colon cancer is possible, particularly if the infection has only spread as far as the wall of the colon.

Change in Bowel Movements

Almost all people with colon cancer experience changes in bowel movement patterns. They may begin to have recurrent bouts of diarrhea or constipation for no identifiable reason. Given the non-specific nature of randomly occurring bowel disturbances, these signs are often not taken seriously, and people may choose to treat them using over-the-counter medications, rather than seeking medical input. However, if the symptom does not resolve quickly, it is essential to see a doctor.

Abnormal Stool Quality

Stool quality tends to change once an individual develops colon cancer. Some people have long, thin “pencil stool,” which is thinner than usual stool. In some cases, the stool’s color may also be abnormal, sometimes appearing dark due to bleeding in the digestive passage; it may also contain visible blood. Such signs are hard to miss, especially if this unusual stool quality is not a one-time occurrence but persists for a long time.

Rectal Bleeding

Colon cancer may cause bleeding in the lower digestive passage. In some cases, bleeding can even happen in the rectum. In the case of rectal bleeding, blood is visible as a separate discharge in the stool. Rectal bleeding is common in individuals who have more bouts of constipation than diarrhea as the disease progresses. Bleeding in the lower digestive passage above the rectum can change the color of stool. Look out for black, tar-like stools, which can indicate bleeding higher in the colon. Bleeding lower in the colon and from the rectum is often bright red.

Abdominal Discomfort

People with colon cancer often experience abdominal pain, sometimes on a daily basis. The disease can cause feelings of excessive fullness and bloating, even if one has not eaten. Pelvic pain and stomach cramps, and even gas and belching, can develop. These symptoms are common signs of several other conditions, such as GERD, IBS, and frequent indigestion, and thus tend to be misdiagnosed.

Nausea and Vomiting

Not all of those who develop colon cancer experience nausea and vomiting. In some cases, however, abdominal discomfort is accompanied by the urge to vomit, which may or may not provoke the physical reaction.

Loss of Appetite

In a significant number of colon cancer cases, people lose their appetites. This reaction is not entirely understood. One possibility is that abdominal discomfort puts people off food, so they instinctively avoid eating much. In cases where there aren’t many symptoms, like abdominal pain, bloating, and gas, the reason for the loss of appetite is difficult to pinpoint.

Decrease in Weight

Doctors attribute weight loss associated with colon cancer to various factors, including appetite loss leading to under-consumption of nutrients. Cancer cells divide more rapidly and require more calories than normal cells due to their rapid growth rate. The body also expends additional energy and resources trying to fight the tumor. In some people, this leads to weight loss.

Unexplained Fatigue

Colon cancer takes a toll on energy levels. The immune system kicks into overdrive, thus leading to increasing energy consumption in the body. Cancer cells are more energetically demanding and use up more resources than normal cells. Fatigue may also occur due to loss of red blood cells that contain iron from the colon or rectum; this degree of bleeding may be microscopic and not visible. People with colon cancer who do not eat enough to offset this increased consumption are likely to feel weak, lethargic, and sleepy for no obvious reason.


Older individuals with colon cancer, especially men and women over the age of 50, tend to develop iron-deficiency anemia after the onset of the condition. Anemia produces another range of symptoms, including weakness and general malaise. In very severe cases, cardiac problems such as palpitations and angina may present, though these are rare.

Shortness of Breath

Some individuals with colon cancer report frequently feeling short of breath. In most instances, this occurs in older adults who also have anemia. Shortness of breath implies increasing pressure on the cardiovascular system, which in itself is a serious health hazard. Such a symptom calls for prompt medical attention.