Rectal Cancer Signs and Symptoms

Rectal cancer is a type of colorectal cancer found in the lower portion of the colon near the anus.

It's important to be able to recognize symptoms of rectal cancer. This is because the longer it takes to get a diagnosis, the more likely it is that the cancer will be found at an advanced stage of the disease, when the outlook isn't as good. (However, symptoms of rectal cancer are nonspecific. This means they could have a number of causes besides rectal cancer. )

While people over 50 are generally at higher risk of colorectal cancers, the number of cases in people under 50 has been rising significantly. Because of this, the American College of Gastroenterology revised its guidelines 2021. Instead of being screened for the disease at age 50, the guidelines now recommended screening at age 45 for people who are considered average risk.

This article will describe signs and symptoms that could be caused by rectal cancer. If you notice one or more of them, contact your healthcare provider.

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. Sometimes, there is mucus in the stool as well.

Bleeding may not always be obvious, 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. Keep in mind that 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 unusual changes in stool color to your healthcare provider.

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

Changes in Bowel Habits

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

The important thing to remember is that a change in bowel habits means a change for you personally. Everyone has different bowel habits, and what is normal for one person may not be for another.

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 that occurs more than a few times.

Rectal Pressure

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

Thin Stools

A change in the size and shape of a bowel movement may indicate a problem, especially if you notice thin or ribbon-like stools.

A growth in the colon or rectum that is partially obstructing (blocking) 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 cramping that worsens over time. Small amounts of liquid stool may be able to pass through the obstruction, but you will still feel constipated.

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. Other symptoms include shortness of breath, 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 habits, 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.

Summary

Symptoms of rectal cancer include blood in the stool, a noticeable change in your bowel habits or shape and size of your stool, and unexplained weight loss.

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. Delaying a diagnosis can make it more likely that the disease will have time to become more advanced.

A Word From Verywell

Having an awareness of the signs and symptoms of rectal cancer is important in order to detect and treat these cancers as early as possible. If you notice any of the symptoms discussed in this article, talk to your doctor, even if you think you are too young to have colorectal cancer. Your doctor can refer you to a specialist for evaluation if they think the symptoms are concerning. Even if you aren't having symptoms of rectal cancer, a healthcare provider can advise you on how and when to be screened for the disease.

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, having a 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 rates 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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13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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