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Home of Sidney Kimmel Medical College

Bloody Stool: Is It Colon Cancer or Is It Something Else?

It can be alarming to see blood in the toilet or when wiping after a bowel movement, but in most cases, it isn't a sign of a life-threatening disease.

Finding blood in your stool can be an incredibly frightening experience, and it is likely more common than we know. Bloody stool can indicate something minimal, such as a hemorrhoid, or something much more worrisome, such as an inflammatory bowel disease or even cancer.

If you’re stumbling upon this article, you may have already read that different colors and presentations of blood can indicate different conditions. This is true–sometimes, according to gastroenterologist Dr. Donald McMahon.

Decoding the colors and presentations of blood

Bright red blood typically comes from a source lower down in the gastrointestinal tract (colon or rectum) and can point to hemorrhoids, fissures, colon cancer, ulcerative colitis, diverticulosis, or a Crohn’s disease flare, Dr. McMahon states.

Black and tar-like blood usually comes from higher up, such as in the esophagus or the stomach, and often points to ulcers, Dr. McMahon adds. He says that some sources suggest that the consumption of certain foods–such as blueberries or cranberries–as well as certain medications, can also mimic a blood-like color.

The bottom line is there are countless causes for GI/rectal bleeding, says Dr. McMahon. “If you see any blood in your stool, you should seek a medical opinion as soon as possible.* You shouldn’t just assume you’re okay when you could have something serious going on.”

Unfortunately, colon cancer, like most cancers, develops silently. It’s rare to have symptoms until it’s metastasized, or spread, adds Dr. McMahon. “In my 13-plus years of experience, I can actually remember the specific patients who’ve had cancer present with symptoms; that’s how rare it is.”

Knowing the warning signs of colon cancer

Warning signs of late-stage colon cancer, aside from bloody stool, may include persistent abdominal pain; unexplained weight-loss; pencil-like stool; changes in overall bowel habits; anemia from chronic blood loss (typically due to occult/hidden blood in the stool); chest pain; and shortness of breath upon exertion.

How would a diagnosis be made? An individualized approach is taken for everyone, but the key factors looked at are age and presentation, says Dr. McMahon. “If you come to me at 20-years-old with abdominal pain and rectal bleeding, we’re going to look into chronic conditions like inflammatory bowel disease, such as ulcerative colitis. If you come to me at 45-years-old with these same symptoms, I’m going to recommend a colonoscopy.”

The good news: colon cancer is one of the most preventable cancers there is. “All we need to do is listen to our bodies, our doctors, and the recommended screening guidelines,” said Dr. McMahon.

The American Cancer Society recommends colon cancer screening starting at age 45, or earlier if you have a family history. Colonoscopies are the standard for colon cancer screening, as they can discover and remove polyps–or abnormal growths–before they become cancerous. If and when cancer is found, at an early stage, it is completely treatable/curable.

If you have a history of one of the GI conditions discussed above and start to notice anything out of the ordinary, it may be a cause for concern (although not definitively colon cancer) and should be discussed with your doctor sooner, rather than later, notes Dr. McMahon.

The next time you experience rectal bleeding–or any suspicious GI symptoms, for that matter–Dr. McMahon says to keep these three things in mind:

  • Immediate answers are desirable, however, they’re not realistic (or safe) when it comes to our health. The internet is not your GI specialist; we’re here and available to do the appropriate work-up.
  • Do not ignore or brush off your symptoms out of hesitance over having testing done. You may not always need a colonoscopy.
  • Even if you do need a colonoscopy, the procedure itself is painless; the prep is the worst part, and the risk of having one done isn’t as nearly as great as the risk of what can potentially develop if you don’t have one.

*If you experience a large amount of blood coming from the rectum, you may be hemorrhaging and should call 9-1-1 or head to your local Emergency Department. 

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From the Experts, Healthy You