Rectal Cancer Symptoms and Signs

In the early stages of the disease, rectal cancer symptoms may not be present. As it progresses and symptoms do appear, they can include: 

• Vague abdominal pain
• Blood in the stool
• Changes in the shape of the stool
• Persistent diarrhea or constipation
• Fatigue
• Unexplained weight loss

Many of the signs of rectal cancer, however, are nonspecific. This means they can be caused by many other conditions—not just cancer.

It is important to see a healthcare provider if you notice them. If it does turn out that you have rectal cancer, an early diagnosis can improve treatment outcomes. When diagnosed at an advanced stage, the prognosis is usually much worse.

Read on to find out more about the signs and symptoms of rectal cancer, which tend to be the same in both males and females.

Changes in Bowel Habits

A change in bowel habits is a common sign of rectal cancer. 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 your healthcare provider if you notice any change occurring more than a few times.

Constipation or Diarrhea

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.

Narrow or 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 isn't an accepted definition. If you notice that your stools are thinner than normal, see your healthcare provider.

Abdominal Pain or Cramping

The most common presenting symptom of colorectal cancer is abdominal pain; however, it's very vague and non-specific. There are many reasons why a person may have abdominal pain or cramping, and much of the time the reason is not cancer. This is why it may not be worrisome at first.

With colorectal cancer, the pain can be occasional or constant. It can be localized or general discomfort. Many times, there will be other symptoms like blood in the stool.

If you are having abdominal pain or cramping for no reason, and it persists, call your healthcare provider. Take note of other symptoms that may also be present, like bloody stools or pain with bowel movements.

Bloody Stools

Rectal bleeding (either bright red or dark red) is a common symptom of rectal cancer. Sometimes, there is mucus in the stool as well.

Bleeding may not always be obvious, but 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 some foods, like beets and red licorice, can cause changes in stool color that resemble blood.

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.

Rectal Pressure

Another common symptom of rectal cancer is 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 cause this sensation of incomplete emptying (tenesmus), even if you no longer need to pass stool.

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, it could be a sign of rectal cancer.

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, but unexplained weight loss always warrants a visit to your healthcare provider.

Conditions With Similar Symptoms

The symptoms of rectal cancer can sometimes be mistaken for the symptoms of common, less serious conditions such as hemorrhoids or irritable bowel syndrome (IBS).

There are subtle differences, however, in the way these conditions present.

For example, hemorrhoids usually get better with home care, while rectal cancer causes worsening symptoms over time. Hemorrhoids also come and go and don't happen alongside other symptoms like fatigue or weight loss.

Similarly, IBS does not cause bleeding, fatigue, or weight loss.

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. These symptoms can also occur with many other diseases.

Awareness of the signs and symptoms of rectal cancer is important to detect and treat these cancers as early as possible. If you notice any of the symptoms discussed in this article, talk to your healthcare provider, even if you think you are too young to have colorectal cancer.

A Word From Verywell

Colorectal cancer is increasing in people under age 55, with a significant increase in 30- to 39-year-olds noted since 1995 and a rise in 40- to 54-year-olds noted since 2005. Unfortunately, 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.