Rectal Cancer Signs and Symptoms

Being able to recognize the signs and symptoms of rectal cancer—colorectal cancers found in the lower portion of the colon near the anus—is more important than ever following a 2017 study.

Researchers discovered that colorectal cancer is increasing significantly in people under the age of 50. This uptick prompted the American College of Gastroenterology to suggest in its 2021 guidelines that colorectal cancer screenings begin at age 45 for people who are considered average risk.

Unfortunately, whether the disease occurs in younger or older adults, a delay in the diagnosis of this disease is a problem. Frequently, this results in these cancers being found at more advanced stages of the disease, when the outlook isn't as good.

The signs and symptoms of rectal cancer are nonspecific, meaning they could have a number of causes—many, though not all, of which are less serious. While the chance that you might have rectal cancer is higher if more than one of the following are present, experiencing just one of these signs or symptoms is reason enough to see your healthcare.

rectal cancer symptoms
Verywell / Gary Ferster

Bloody Stools

Rectal bleeding (either bright red or dark red in color) is a common symptom of rectal cancer. This bleeding may be associated with the passage of mucus in the stool as well.

Bleeding may not always be apparent, however, and sometimes it occurs only on a microscopic scale (meaning you can't see it with the naked eye). A test called a fecal occult blood test (FOBT) detects blood in the stool that cannot be seen.

While rectal bleeding is a symptom of rectal cancer, it is also associated with less severe health problems, such as internal hemorrhoids and anal fissures. There are also some foods, like beets and red licorice, that can cause changes in stool color that resemble blood.

To be safe, always report any suspect changes in stool color to your healthcare provider.

While bleeding due to rectal cancer usually causes bright red or dark red blood (hematochezia), don't dismiss darker stools. Bleeding higher in the colon, as well as in the stomach, often appears black and tarry (melena), or resembles coffee grounds. This symptom can also be a warning sign of serious medical conditions.

Changes in Bowel Habits

Another common symptom of rectal cancer is a change in bowel habits. This can be diarrhea, constipation, or an increase or decrease in the frequency of bowel movements. With rectal cancer, diarrhea is quite common.

The important point with bowel habits is to be alert for a change that represents a change for you personally. Everyone has different bowel habits, and what is normal for one person may not be for another.

Certainly, there are many causes of this, and your symptoms could be due to something as minor as your diet. That said, it's still best to consult with your healthcare provider if you notice any change.

Rectal Pressure

Another common symptom of rectal cancer is the presence of rectal pressure or fullness, or the sensation that you have to empty your bowels, even if you've just finished. A mass in the rectum can give the sensation of incomplete emptying (tenesmus), even if you no longer need to pass stool.

Thin Stools

A change in the pattern of a bowel movement to thin or ribbon-like stools may indicate a problem. A growth in the colon or rectum that is partially obstructing the bowel can change the size and shape of the stool as it exits the body. Other conditions may also cause thin stools, such as a large benign polyp or hemorrhoids.

While some sources describe thin as "pencil thin," there really isn't an accepted definition. If you notice that your stools are thinner than normal for you, see your healthcare provider.

Cramping and Constipation

When a tumor in the rectum is large, it may obstruct the rectum partially or completely. This can lead to severe constipation and progressively worsening cramping. Small amounts of liquid stool may be able to pass through the obstruction, but the sensation of constipation will persist.

If you are passing liquid stool and feel like you need to expel more waste, but can't, urgent medical care is needed.

Symptoms of Anemia

Microscopic bleeding due to rectal cancer often causes anemia. Anemia, in turn, can cause fatigue (commonly the first symptom people note) or weakness; shortness of breath, often just with activity at first; dizziness; headaches; and an irregular heartbeat.

Most people feel tired at times, but fatigue that is interfering with your ordinary activities could be a symptom of an underlying medical problem.

Unexplained Weight Loss

Many people welcome unexpected weight loss, but if you're losing weight and haven't changed your diet or exercise, there is cause for concern.

Unintentional weight loss is defined as the loss of more than 5% of your body weight over a six- to 12-month period without trying. An example would be a 200-pound person losing 10 pounds over a six-month period.

Rectal cancer is only one of the possible causes of this symptom, however, so unexplained weight loss always deserves a visit to your healthcare provider.

A Word From Verywell

Colorectal cancer is increasing in people under age 55, with a significant increase in 30- to 39-year-olds being noted since 1995, and an increase in 40- to 54-year-olds noted since 2005. Experts cannot pinpoint the reason. At the same time, the diagnosis of these cancers is often delayed. Consequently, the tumors are often more extensive, making treatment more difficult.

Having an awareness of the signs and symptoms of rectal cancer, and seeking attention if you note any of them, is important in order to detect and treat these cancers as early as possible.

Frequently Asked Questions

  • What causes colorectal cancer?

    Risk factors for colorectal cancer that cannot be controlled include being older, a history of colorectal cancer or polyps, certain genetic conditions, a history of inflammatory bowel disease, and your racial and ethnic background. Risk factors that can be modified include being overweight or obese, sedentary lifestyle, a diet high in red or processed meat, low vitamin D levels, smoking, and excessive alcohol use.

  • What is the survival rate for colorectal cancer?

    The five-year relative survival rates for colon cancer that remains localized, spreads regionally, or spreads to distant areas of the body are 91%, 72%, and 14%, respectively. The five-year survival rate for rectal cancer that remains localized, spreads regionally, or spreads to distant areas are 89%, 72%, and 16%, respectively.

  • Can you do anything to self-check for colorectal cancer at home?

    Certain colorectal cancer screening tests come as kits in which you take a stool sample at home and send it in for analysis. These include a fecal immunochemical test and a guaiac-based fecal occult blood test, both of which look for blood in stool; and a stool DNA test, which looks for certain DNA markers that can indicate cancerous changes in cells.

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15 Sources
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