Colon and rectal cancers do not usually produce symptoms in the early stages of disease. As the tumor grows, symptoms will depend on the location of the primary tumor within the intestine.
Patients with colon cancer or rectal cancer may experience one or multiple symptoms. These may include the following:
Blood in the Stool
You may notice obvious blood the stool, or darker colored bowel movements, which may indicate that there is bleeding within the intestinal tract or rectum. Sometimes bleeding may be present but not visible. This is called occult (hidden) blood and may not be discovered until a blood test indicates a low red blood cell count.
Bright red blood in the stool typically indicates that there is bleeding in the rectum or colon, which may be a sign of colon or rectal cancer. Rectal bleeding can also be caused by hemorrhoids. Typically, patients with hemorrhoids experience symptoms that come and go with flare-ups, whereas rectal bleeding caused by cancer usually continues or worsens and is more likely to be accompanied by pain.
Changes in Bowel Habits
Changes in bowel habits that can indicate colon or rectal cancer include the following:
New-onset constipation or diarrhea
Changes in frequency or size and caliber of bowel movements
A bowel that doesn’t seem to empty completely
Stool that is narrower than normal (even as thin as a pencil)
Occasional bowel changes can be caused by a dietary change, disagreeable food or a viral/bacterial infection. However, if you are experiencing something new and unexplained—and it lasts more than a couple of days—see your doctor.
More Information About Colon Health from Johns Hopkins Medicine
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Ever curious what bowel changes could signal about your health? Poop may be a gross topic that no one likes to talk about, but taking a quick peek before you flush may give you clues about your health.
Abdominal Pain and Bloating
Stomach bloating, distention, cramps or pain in the abdominal or bowel region can be symptoms of colon or rectal cancer. These are common issues that can also be caused by a number of conditions, including diet-related gastrointestinal distress, Crohn’s disease or ulcerative colitis. See your doctor if you experience frequent abdominal pain and bloating that does not have an obvious cause.
Nausea and Vomiting
Nausea and vomiting can occur if a colon or rectal tumor is obstructing the bowel and inhibiting the passage of liquid or solid waste or gas. Bowel blockage can also be accompanied by painful abdominal cramps, bloating and constipation.
Nausea and vomiting are symptoms of a range of conditions, which may be benign or serious. If you experience persistent nausea, signs of dehydration or vomiting that lasts for more than 24 hours, seek immediate medical treatment.
Anemia is a blood disorder characterized by a deficiency of red blood cells or hemoglobin. In patients with colon or rectal cancer, intestinal bleeding may cause anemia. Depending on the location of the bleeding within the colon, anemia can be the first sign that blood loss is occurring.
Common symptoms of anemia include skin pallor (paleness), increased heart rate, fatigue, dizziness and irregular menstruation.
Unexplained Weight Loss, Loss of Appetite and Feeling Weak
Losing weight, losing your appetite or feeling weak are all possible signs of colon or rectal cancer along with many other unrelated conditions. In patients with colon or rectal cancer, these symptoms are usually related. Persistent diarrhea can cause weight loss. Stomach pain and nausea can reduce your appetite so that you don’t consume enough food to maintain your weight. All these issues, as well as anemia, can lead to weakness.
Pain in the pelvic area is not common in patients with colon or rectal cancer. If it occurs, it may indicate that the cancer has spread to the pelvic area.
More Information About Colon Cancer in the Health Library