fbpx Colorectal Cancer Screening, Symptoms and Diagnosis

Colorectal Cancer Screening, Symptoms and Diagnosis

March is the Awareness Month for one of the most common types of cancer in the United States.
Kurtis Bright
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Kurtis Bright

"Raising awareness" is such a tricky phrase.

It's a nice idea. Loads of well-meaning people have the best intentions when trying to raise awareness for this issue or that issue by signing online petitions, clicking the "like" button or retweeting something.

But let's be real: The vast majority of the time, being aware of issues facing us isn't what stands in our way. We know what the problems are. The question is, what are we going to do about them?

Colorectal Cancer Awareness Month in March gives everyone an opportunity to answer that question. Raising awareness of the third most common type of cancer for men and women in the United States can save lives—not tomorrow, not someday, not theoretically, but today, for you or someone you love.

That's not hyperbole or exaggeration. Certain types of screening for colorectal cancer can remove the threat of it in real-time.

"The nice thing about colorectal cancer—well, there's nothing 'nice' about cancer—but colorectal cancer is one that you can actually screen for and prevent to a large degree, which is not something that's true of all cancers," said Shahrad Hakimian, M.D., a gastroenterologist with UCLA Health in Los Angeles. "We can basically prevent cancer from happening or catch it at a much earlier stage where it's more easily treatable and even curable."

Here's what you need to know about colorectal cancer screening, symptoms and diagnosis.

Colorectal cancer just hits different

As the name implies, colorectal cancer is cancer of the colon or rectum, which consists of the upside-down-U-shaped part of the large intestine and continues into the rectum, terminating with the anus.

Anomalous growths called polyps develop in the colon over many years in 15 percent to 40 percent of people. These polyps subsequently develop into cancer in 4 percent to 5 percent of the population.

Both men and women can develop colon polyps and colon cancer, but men are at a slightly higher risk.

Here are some risk factors for colorectal cancer:

  • Being older than 45
  • Family history of colorectal cancer, especially in a first-degree relative, such as a parent or sibling
  • Having an inflammatory bowel disease, such as Crohn's disease or ulcerative colitis
  • Eating too much red meat and certain processed meats and not enough fiber
  • Being overweight or obese
  • Lack of physical activity
  • Smoking
  • Being African American—they have the highest rates of colon cancer incidence and mortality of all racial groups in the United States
  • Being Jewish of Eastern European descent—they have one of the highest colon cancer rates of any ethnic group worldwide

Some other potential risk factors include being a heavy drinker, cooking meat at high temperatures (such as when frying or grilling) and having diabetes, but the evidence supporting these factors is less clear.


People often experience no visible symptoms of colorectal cancer. If symptoms do appear, that's usually bad news, because it means the cancer has progressed.

"More advanced cancer can cause blockages in the colon, bowel obstruction, distention, vomiting and things like that, but that is typically very advanced and indicates a very large mass," Hakimian said. "The vast majority of people don't get that."

Some other symptoms include:

  • Changes in the bowels, such as constipation or diarrhea that lasts for more than a few days
  • The diameter of your stool gets narrower
  • A feeling like you need to poop that doesn't go away even after you've gone
  • Bleeding bright-red blood from the rectum
  • Bloody stool that may look dark brown or black
  • Abdominal pain or cramping
  • Overall fatigue and weakness
  • Unintentional weight loss
How does screening work?

Let's talk colonoscopy, the most common, accessible and effective kind of screening available.

"So the whole purpose of colorectal cancer screening is to identify anybody at risk, which basically means now, anybody over the age of 45 should do a colonoscopy so we can go in and take out those polyps preemptively, so they don't turn into colon cancer," said Niket Sonpal, M.D., a gastroenterologist, internist and assistant professor at Touro College of Osteopathic Medicine in New York City.

As Sonpal alluded to, the amazing aspect of colorectal cancer screening is that it is simultaneously colorectal cancer prevention.

Here's how it works: The procedure takes 30 to 60 minutes. Depending on the gastroenterology center you visit, you receive either twilight sedation or full sedation, so you're drowsy or asleep through the procedure.

"The day before the procedure, you're on a clear liquid diet, so you don't allow your body to have any food that's solid or fatty—just clear liquids," Sonpal said. "And then we give you a solution to clean out your colon, a laxative. When you come in the next day, we use a camera that's at the end of a long tube. We have medicine that makes you comfortable—asleep or sleepy—then we go in through the rectum and we go all the way around the colon."

Once the scope reaches the upper end of the colon, the gastroenterologist begins working backward, drawing it back toward your rectum. Using the camera, they look for polyps, which are often as tiny as a few millimeters across up to a centimeter and a half.

Included within the scope's tube is an instrument channel that contains a snipping tool that can be extended when the doctor finds a polyp. Then they simply snip it off, and the polyps are then collected and sent off to a pathologist for analysis.

After the procedure, you're given time to recover from the sedative, but you must have someone drive you home. You're no longer on any diet restrictions, and most people go back to work the next day.

The tropes surrounding colonoscopy—and the fact it involves the butt—make some people hesitant to get one. They may believe the procedure is highly uncomfortable or even painful.

Gastroenterologists, however, are quick to debunk these views.

"I can assure people we do these with a good amount of sedation," Hakimian said. "Most patients feel absolutely no discomfort during the procedure. Many wake up after the procedure and ask when we're starting, they're so comfortable through the whole thing."

Other screening tools

Stool tests can be used to check your fecal matter for evidence of cancer. You can get a kit and instructions from your healthcare provider to collect samples at home and mail them in for analysis.

Fecal immunochemical test (FIT)

The FIT test looks at a stool sample for hidden blood that's not visible to the naked eye, which is often an indication of a larger polyp or full-blown cancer. This test should be done annually.

Guaiac-based fecal occult blood test (gFOBT)

The gFOBT test also looks for hidden blood in your stool, but uses a chemical reaction to do so. It's another one that should be done annually.

Stool DNA test

This test searches your stool for abnormal DNA that has been shed by a polyp or cancerous cells and also checks for hidden blood. Every three years is the suggested frequency for the stool DNA test.

CT colonography (virtual colonoscopy)

A virtual colonoscopy can be used on people who can't have or don't want a typical colonoscopy. It involves using a computer-assisted combination of X-rays and computed tomography (CT) scans to get a 3D image of the colon and rectum.

An important fact to remember about all the alternatives to a standard colonoscopy is that while they're good at detecting lesions that have developed into cancer, they're less useful for the early detection of polyps. For some clinicians, the tests fall short.

"[These] tests are not as good as the colonoscopy," Sonpal said. "And if you don't do a colonoscopy-based test and something is found, then you still have to get a colonoscopy. The whole point is that we stop the cancer before it happens. You can reduce, some statistics say, the incidence of colon cancer by 90 percent."

Diagnosis and staging

But let's say the worst happens, and someone develops colon or rectal cancer. How is it diagnosed and evaluated?

The first step is for the doctor to use the colonoscope and its embedded snipping tool to take a biopsy of any suspicious-looking lesions and send the sample to a pathologist for evaluation.

The next step is to determine whether the cancer is localized or has spread. This usually means the patient goes in for a CT scan to get a better idea of the extent of the cancer.

A very nuanced and specific set of staging criteria categorizes cancer based on precisely how far into the colon wall it has grown and whether it has spread to nearby lymph nodes or distant parts of the body.

"Normally, after you detect the cancer, you proceed with some kind of imaging to see if we see distant spread," Hakimian said. "Usually, with just colonoscopy and biopsy and pathology, we can diagnose the cancer itself. But to kind of truly know the stages of cancer, you need surgery to remove some of the colon to look at the whole thing under a microscope to determine if there's evidence of spread."

Consultations with an oncologist and a closer study of the colon and surrounding structures determine the path forward.

What's next?

The second part of this series during Colorectal Cancer Awareness Month will go into more detail about treatment, side effects and life after colorectal cancer.

The important takeaway is that gastroenterologists urge people to understand how useful screening for precancerous polyps is for preventing cancer from developing in the first place.

"Prevention is the best treatment in many cases," Hakimian said. "It being a fairly common cancer and a common cause of cancer death, it's very important for people to pay attention to this and undergo the proper screening. We have such good tools."

Taking advantage of those tools could save you and your loved ones a great deal of unnecessary loss and heartache.