A gastroenterologist discusses differences between colon cancer diarrhea and the diarrhea caused by IBS.
Do they look the same? How are they different?
You may have read that “constipation alternating with diarrhea” is a possible symptom of colon cancer.
The alternating feature here is a red flag (though benign conditions can also cause this).
But what about just plain diarrhea…without any constipation?
“Diarrhea is a rare symptom of colon cancer,” says Pankaj Vashi, MD, Lead National Medical Director, National Director, Gastroenterology/Nutrition/Metabolic Support, Cancer Centers Treatment of America.
“Diarrhea is usually related to travel, food allergy/intolerance or inflammation/infection in the bowel. Chronic diarrhea can be seen in IBS.
“Every patient with diarrhea should have a thorough evaluation including a detailed history and physical, stool, radiological and endoscopic studies before labeling it to be secondary to IBS.
“Diagnosis of IBS in a patient is usually made after excluding other treatable conditions.”
Don’t accept a diagnosis of irritable bowel syndrome until every other possible cause of your diarrhea has been ruled out, and that will require extensive testing.
Sudden-onset diarrhea, in the absence of having recently traveled or taken a new medication that can cause the side effect of diarrhea, can be alarming.
This happened to me. Where did my diarrhea suddenly come from? And it looked really weird, too.
Right away, the gastroenterologist’s nurse, as I was being prepped for a colonoscopy, mentioned that it could be IBS.
He also mentioned that it could be stress related, and he told me that his divorce had caused him to have diarrhea for three weeks.
But I was betting that his diarrhea didn’t look abnormal like mine did.
A doctor needs to look inside your colon, among other tests, before it’s determined that you have IBS.
Diarrhea, even weird looking, is a common symptom in the mass of population, though it CAN be caused by colon cancer. But it’s not a hallmark feature of colon cancer.
My diarrhea turned out to be caused by microscopic colitis (colon tissue samples are viewed under a microscope for diagnosis), a benign condition that does NOT increase the risk of colon cancer.
For 20 years 
