You may know that colorectal cancer, which includes colon cancer and rectal cancer, is one of the most common types of cancer in adults. You may also know that as colorectal cancer progresses, signs can include changes in bowel habits and digestion. So, perhaps you’re wondering if you should be concerned about symptoms like bloody poop, constipation or stomach pain.
The first thing you need to know is that if you’re experiencing any strange symptoms, it’s likely not cancer. A range of different conditions can cause these types of symptoms, and most aren’t serious. But it’s also important to not ignore what you’re feeling.
What are possible colon cancer symptoms and how might you be able to tell them apart from other conditions? How is colorectal cancer diagnosed? We answer these questions and more below.
Early signs of colon cancer and rectal cancer may not be noticeable
Like with most cancers, many people don’t experience colorectal cancer symptoms early on. That’s because colorectal cancer usually starts as polyps (clumps of tissues) that form inside the colon or rectum, and polyps don’t typically cause symptoms.
This is why routine colorectal cancer screening is recommended, usually beginning at age 45. Screenings can find and remove polyps that could be cancerous or become cancerous.
Common symptoms of colon cancer and rectal cancer include changes in bowel habits and digestion
As colorectal cancer progresses, it can start to cause noticeable symptoms. Most commonly people will notice changes to digestion and bowel habits, but symptoms can depend on the size of the cancer and where it is in the colon or rectum.
If you notice any of the following symptoms, they’re likely caused by something else. But it’s still a good idea to make a primary care appointment and talk to your doctor since these symptoms can be signs of other conditions that should be treated.
Rectal and colon cancer can cause rectal bleeding, leading to bloody poop
Rectal bleeding is the name for blood that leaves the body through your anus or rectum, but the blood can originate higher up in your digestive system. Signs of rectal bleeding can be bloody poop, blood in the toilet water and blood on toilet paper. Depending on where and when the bleeding happens, poop may look bright red, dark red or even black.
Changes in bowel habits or poop shape can be a sign of cancer in the colon or rectum
Healthy poop comes in different shapes, sizes and frequencies. It’s also common to have days where you’re in the bathroom much more or much less than you’d like. But you shouldn’t ignore changes in bowel habits that last more than a couple of weeks.
Colorectal cancer can cause frequent diarrhea and chronic constipation. It may also cause poop to suddenly be thin like a pencil. But keep in mind that medicines, lifestyle and medical conditions can also affect bowel habits, and chances are that your symptoms aren’t caused by colorectal cancer.
People with colorectal cancer may lose weight without trying
Unexplained weight loss can be a sign of colorectal cancer and other medical conditions. While it’s normal for weight to go up and down, it can be concerning if a person’s weight trends down over a period of 6-12 months.
How much weight loss may be concerning? If your starting weight was over 200 pounds, talk to your doctor if you lose more than 10 pounds in a short period of time, without trying. If you weigh less than 200 pounds, let your doctor know if you lose more than 5% of your body weight.
Fatigue from colorectal cancer can feel like whole-body tiredness
It’s normal to feel worn out from time to time, especially if you’ve had a stressful day or have been especially active. But your body should feel better once you’ve had time to recover. Fatigue that’s caused by medical conditions like cancer may not go away, even after you sleep or rest.
Colorectal cancer can make it feel like bowels aren’t totally empty after pooping
Incomplete bowel emptying can make a person’s bowels feel full after they poop. This can be caused by digestive disorders, chronic constipation and pelvic floor disorders. Colorectal cancer is a less likely cause, but it can sometimes happen if a tumor is blocking part of the colon or rectum.
If you experience this symptom occasionally, it’s most likely caused by your diet. But if you frequently feel like your bowels remain full after going to the bathroom, it’s time to talk to your doctor.
Stomach discomfort from colorectal cancer includes bloating and cramping
If your tummy hurts, it’s probably not cancer. Stomach discomfort is incredibly common and can be caused by eating habits, medical conditions and even emotions. Abdominal discomfort – such as abdominal cramping and a dull stomachache – caused by colorectal cancer doesn’t go away and may worsen over time. Some people may feel full or bloated, even after eating small amounts of food.
Depending on the location of the cancer, there may also be pain in a specific area. For example, tumors on the right side of the colon may cause pain in the upper right abdomen, while those on the left side of the colon may cause pain in the lower left abdomen.
Symptoms of more advanced colorectal cancer can affect other organs
As colorectal cancer progresses, it spreads throughout the body. Most often it spreads to the liver, but it can also spread to the brain, bones and lungs. And when it spreads, it can cause symptoms related to other organs and tissues affected by the cancer. Possible Stage 4 colon cancer symptoms include:
- Liver symptoms – Jaundice (yellowing of the skin and eyes), abdominal swelling and pain
- Lung symptoms – Shortness of breath, a cough that won’t go away and chest pain
- Bone symptoms – Bone pain, fractures and swelling
- Brain symptoms – Headaches, vision changes and neurological symptoms
If you start to notice any of these symptoms, seek medical care right away.
Symptoms of colorectal cancer in women vs. men
You may have heard that colon cancer symptoms in men are different than colon cancer symptoms in women, but that’s not the case. Colorectal cancer symptoms are the same for everyone.
However, women are more likely to experience some of these symptoms for other reasons. Women are naturally more likely to be constipated. And during menstruation, they can experience cramping and bloating. Plus, they are more likely to have digestive disorders that share symptoms with colorectal cancer.
How to tell if symptoms are from colorectal cancer or another condition
Colorectal cancer symptoms can also be signs of other medical conditions. There are some differences, which we highlight below, but they can be hard to spot. Talk to your primary care doctor if you have symptoms that last more than two weeks, even if you think they are caused by another condition.
Symptoms of hemorrhoids vs. colorectal cancer
Hemorrhoids are swollen veins around your anus. They’re not usually serious and are much more common than colon cancer. In fact, about half of people over 50 have inflamed hemorrhoids. In contrast, about 4% of people are diagnosed with colorectal cancer.
Symptoms of hemorrhoids can be similar to symptoms of colon cancer. For example, both can cause rectal bleeding and lumps in the anus. Hemorrhoids are the most common cause of rectal bleeding or bright red blood in the toilet. Hemorrhoids also cause itching and pain around the anus. However, hemorrhoids are unlikely to cause belly discomfort, changes in bowel habits or unexpected weight loss.
Symptoms of irritable bowel syndrome vs. colorectal cancer
Irritable bowel syndrome (IBS) is a common digestive disorder that causes a range of gastrointestinal symptoms. When a person has IBS, their symptoms usually have one or more triggers, such as certain foods, stress, medications, hormones or eating large meals. About 10-15% of adults experience symptoms of IBS, but only half of them have been diagnosed.
Symptoms shared by IBS and colon cancer are constipation, diarrhea, abdominal pain, bloating and incomplete bowel emptying.
There are some key differences as well. IBS symptoms often go away after a bowel movement, and there can be periods where you have no symptoms at all. When the cause is colon cancer, the symptoms are more likely to develop slowly and get worse with time. You’re also unlikely to experience rectal bleeding or unexplained weight loss with IBS.
Symptoms of inflammatory bowel disease vs. colorectal cancer
Inflammatory bowel disease (IBD) is a condition involving chronic inflammation of the digestive tract. This inflammation causes mild to severe symptoms and can make it more likely that you develop other conditions, including colon cancer. About 1.3% of the U.S. population has been diagnosed with IBD.
Symptoms common to both IBD and colorectal cancer can include abdominal pain, cramping, diarrhea, fatigue and unexplained weight loss. Symptoms more likely with colorectal cancer include rectal bleeding and incomplete bowel emptying. Symptoms more likely with IBD include fever, bloating and loss of appetite.
When symptoms begin can be a clue to the cause. IBD is usually diagnosed before the age of 30, though it can be diagnosed at any age. Colorectal cancer is usually found in people older than 50 years old, but it’s becoming more common in younger adults.
People with IBD may also have periods of remission, where they have no symptoms at all. Symptoms of colorectal cancer are ongoing and worsen over time.
Symptoms of female reproductive health vs. colorectal cancer
Cramping, bloating and bleeding are routine complaints for women who menstruate. So how do you know what’s routine and what’s cause for concern?
Listen to your body and talk to your doctor if your symptoms seem different than usual. Let them know if the pain is worse, occurs when you don’t expect it or shows up in a different location.
If you’re seeing blood in the toilet between cycles, talk to your doctor about that too, even if you’re pretty sure it’s not rectal bleeding. You may be part of the 10% of reproductive-age girls and women who have endometriosis, a chronic condition that causes endometrial tissue to grow outside the uterus. This condition can cause bleeding between periods and digestive symptoms, and there are treatments that can help.
Colorectal cancer is diagnosed using one or more of the following tests:
- Colonoscopy – A diagnostic colonoscopy is the main test used to diagnose colon cancer. During this procedure, your doctor uses a camera attached to a long tube to visually examine the lining of your colon for growths, inflammation and sores. If the doctor finds any small polyps, they’ll remove them.
- Proctoscopy – If your symptoms could be caused by rectal cancer, your doctor may recommend a proctoscopy. During this procedure, your doctor examines your rectum using a thin, lighted tube with a camera at the tip. If your doctor finds cancerous tissue, they’re often able to remove it during this procedure.
- Biopsy – During a colonoscopy or a proctoscopy, your doctor may remove a sample of tissue for testing, this is called a biopsy. The sample is sent to a lab, where a doctor examines it for signs of cancer.
- Imaging tests – Your doctor may use imaging tests (such as X-rays, ultrasounds or MRI scans) to help find where the cancer is located in the colon or rectum.
- Blood tests for colon cancer – There’s no blood test that can diagnose colon or rectal cancer. However, blood tests may be able to detect changes that could be signs of cancer. Your doctor may do blood tests to check your blood count and liver enzymes, and to see if your blood contains chemicals produced by colorectal cancer.
At-home stool tests for colon cancer aren’t used for diagnosis
At-home stool tests can’t diagnose cancer and are rarely used if you have colorectal cancer symptoms. They can be useful as a first step in the colorectal cancer screening process, and if the test finds hidden blood, it’s followed by a colonoscopy.
If you have symptoms of colorectal cancer, your doctor will likely recommend that you start with a colonoscopy or proctoscopy since this can help you get answers (and any necessary treatment), sooner.
See a doctor if you think you have symptoms of colorectal cancer
While your symptoms are unlikely to be cancer, it’s best to know as soon as possible. Colorectal cancer treatment is more effective when cancer is found earlier. Plus, it’s likely that there are treatments to help with your symptoms, no matter the cause.
So if you’re experiencing changes with digestion or bowel movements, see a primary care doctor as soon as you can. If you have severe abdominal pain, vomiting or heavy rectal bleeding, seek emergency care.
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