For one thing, many people with colon and rectal cancers (known as colorectal cancer) don’t experience symptoms at all until the disease has reached a more advanced stage, when it is more difficult to treat. This is why screening tests for seemingly unaffected people are of such vital importance. The drop in colorectal cancer deaths over the past few decades is due in part to increased screening efforts that are identifying asymptomatic cancers. A screening test can also identify abnormal growths called colorectal polyps, some of which may be precancerous. When doctors remove potentially dangerous polyps, they are stopping cancer before it starts. Another complication in colon cancer diagnosis and rectal cancer diagnosis is that even when symptoms develop, people with cancer and doctors may both blame other common conditions, such as hemorrhoids or irritable bowel syndrome. What’s more, many younger people assume that colorectal cancer only affects the elderly, so they are liable to ignore symptoms. (1) However, while the vast majority of colorectal cancer is still found in older people, rates in men and women below age 50 are climbing sharply. An American Cancer Society study, published in 2017 in the Journal of the National Cancer Institute, found that people born in 1990 had double the risk of developing colon cancer and quadruple the risk of rectal cancer as someone born in 1950. (2) In response to this disturbing trend, the American Cancer Society changed its guidelines in 2018 to recommend that regular screening tests for people at average risk of colorectal cancer begin at age 45, rather than 50. (3)
Colon and Rectal Cancer Symptoms and Signs
Whatever your age, the following colon cancer symptoms should prompt a visit to the doctor:
A change in bowel habits — such as persistent diarrhea, constipation, or narrowing of the stool (feces) — that lasts for more than a few daysA feeling that you need to have a bowel movement that’s not relieved by having oneRectal bleeding with bright red bloodBlood in the stool, which may make it look darkCramping or abdominal (belly) painWeakness and fatigueUnintended weight loss
Although people with colorectal cancer may not have rectal bleeding or blood in the stool, these are, for many people, the most identifiable signs of the disease. These symptoms occur when cancer bleeds into the digestive tract. This may occur very slowly over years, and as such, it may not even be noticeable that there is blood in the stool. Over a period of time, this continuous blood loss can lead to a low red blood cell count, a condition called anemia. Blood tests that diagnose anemia may be the first step in the process of getting a colon cancer diagnosis or a rectal cancer diagnosis. (4)
Discussing Symptoms With Your Doctor
Once you describe symptoms to your doctor, they will likely give you a medical exam to ascertain the cause. The doctor will likely question you about your medical history and ask if any of your family members have colorectal cancer, especially parents, siblings, or children. While most people who develop colon cancer have no family medical history of the disease, 1 in 5 do. In rare cases, genetic mutations passed down through families, such as Lynch syndrome, can make a person extremely vulnerable to colorectal cancer. Your doctor will want to know whether you have any other health conditions, particularly those concerning the colon and rectum, that can increase colon cancer risk. This can include a history of colorectal cancer or precancerous polyps or an inflammatory bowel disease such as Crohn’s disease or ulcerative colitis. There’s also an association between type 2 diabetes and colorectal cancer. Other risk factors include obesity or excess weight, a low level of physical activity, heavy alcohol use, and smoking.
A Physical Exam and Blood Tests Are Part of the Workup
Once the doctor has your medical history, the next step might be a physical exam of your body that includes carefully pressing on your abdomen to feel for masses or enlarged organs. The doctor may also examine your rectum by placing a gloved and lubricated finger inside to feel for any abnormalities. The doctor might order blood tests to look for changes that indicate the presence of colorectal cancer. These include not only a test to see if you have anemia but also tests measuring liver enzymes and substances called tumor markers. If you haven’t seen rectal bleeding or blood in the stool, the doctor may advise you to take a test that can identify occult (hidden) blood. These tests, which include a fecal occult blood test and a fecal immunochemical test, involve collecting one or more stool samples at home, packing them in a special container, and returning them to the doctor’s office or a medical lab.
Your Doctor May Suggest a Colonoscopy
You may also leave the doctor’s office with a prescription for a diagnostic colonoscopy. During this procedure, a gastroenterologist examines the inside of the colon and rectum via a device inserted through the anus: a long, thin, and flexible lighted tube with a tiny video camera at the end. If the exam reveals any suspicious growths, the gastroenterologist can remove tissue for a biopsy to determine whether or not there are any cancer cells. The night before a colonoscopy, people having the test need to clean out the colon and rectum. This procedure involves drinking a powerful laxative solution. People having a colonoscopy are typically sedated during the procedure. (5)
