IBS vs. Colon Cancer: How to Tell the Difference

Digestive issues can be more than just an inconvenience – they can disrupt your daily life, cause persistent discomfort and leave you searching for relief. Symptoms like abdominal pain, bloating and changes in bowel habits are often dismissed or attributed to manageable conditions like irritable bowel syndrome (IBS). However, overlooking these gastrointestinal symptoms could mean missing early warning signs of something more serious, such as colon cancer.

To learn more, we speak to Kaylee Knowles, PA-C, a board-certified physician assistant with INTEGRIS Health Medical Group Gastroenterology in Enid. 

"Although IBS does not increase the risk of developing colon cancer, it is important to be alert to the possibility of developing colon cancer and not write off certain symptoms as part of irritable bowel syndrome,” Knowles says. “Sudden unexplained weight loss, rectal bleeding and narrowing of stool are examples of symptoms that should be evaluated in people with IBS to look for other causes including colon cancer.”

What is IBS?

The basics: Irritable bowel syndrome is a common gastrointestinal disorder that affects the stomach and intestines, causing symptoms such as cramping, abdominal pain, bloating, gas and diarrhea or constipation. 

IBS is a functional gastrointestinal (GI) disorder because it causes significant symptoms – abdominal pain, bloating and irregular bowel habits – without any visible structural abnormalities in the digestive tract. 

• This chronic condition can last for years or even a lifetime, with symptoms that vary in intensity and may come and go.
• IBS affects about 10 percent to 15 percent of people in the U.S., making it one of the most common disorders diagnosed by gastroenterologists.
• It’s different from other types of GI disorders because it doesn’t cause inflammation, ulcers or any permanent damage to the intestines or increase the risk of more serious conditions like colorectal cancer.

More recently, IBS has been labeled as a disorder of gut-brain interaction. 

• The gut and brain communicate through a network of nerves, hormones and signals.
• If this connection is disrupted, it can affect how the intestines function.
• For example, this miscommunication can cause abnormal muscle contractions in the gut, leading to diarrhea or constipation, as well as heightened sensitivity that makes normal digestive processes feel painful.

Three main types of IBS exist based on predominant bowel habits.

• IBS with constipation (IBS-C) causes constipation with hard or lumpy stools, along with abdominal pain and bloating, that leads to infrequent and difficult bowel movements.
• IBS with diarrhea (IBS-D) involves frequent diarrhea, loose stools, urgent bowel movements and abdominal cramping, often disrupting travel and daily routines due to its unpredictability.
• IBS with mixed bowel habits (IBS-M) includes alternating constipation and diarrhea, making bowel habits unpredictable and symptom management more challenging.

What is colon cancer?

At a glance: Colon cancer, also known as colorectal cancer when it includes rectal cancer, begins in parts of the large intestine called the colon or rectum. It typically starts as small, noncancerous clumps of cells called polyps that form on the inside of the colon. Over time, some of these polyps can become cancerous. The slow growth makes colon cancer highly treatable, especially when caught in an earlier stage.

Colorectal cancer is the third most common cancer (when excluding skin cancer) diagnosed in both men and women in the U.S.

• In 2024, the American Cancer Society estimated 152,810 new cases of colorectal cancer in the U.S., with 81,540 cases in men and 71,270 in women.
• Colorectal cancer is the second leading cause of cancer-related deaths in the country, with an estimated 53,010 deaths expected in 2024.

The large intestine contains the colon and rectum, which play a key role in waste processing and removal.

• The colon is divided into four sections: the ascending colon, which travels up the right side of the abdomen; the transverse colon, which crosses the abdomen; the descending colon, which travels down the left side; and the sigmoid colon, which connects to the rectum.
• Colon cancer most commonly forms in the sigmoid colon.

Several types of colon cancer exist.

• Adenocarcinoma is the most common type, accounting for about 95 percent of cases, and starts in the glandular cells (responsible for producing mucus and other fluids).
• Carcinoid tumors start in hormone-producing cells in the intestines.
• Gastrointestinal stromal tumors (GISTs) originate in special cells in the wall of the gastrointestinal tract.
• Lymphomas are cancers of immune system cells that can start in the colon.
• Sarcomas start in the blood vessels, muscle layers or other connective tissues in the colon.

How IBS can be confused for colon cancer

At a glance: Irritable bowel syndrome (IBS) and colon cancer can be confused because they share several overlapping symptoms, which can make it challenging to distinguish between the two without medical testing.

Similar symptoms can lead to initial confusion.

• Both IBS and colon cancer can result in diarrhea, constipation or an alternating pattern of both.
• Persistent pain or cramping in the abdomen is common to both conditions.
• Gas and bloating are shared symptoms that may cause a feeling of fullness.
• A sudden need to have a bowel movement can occur in both IBS and colon cancer.
• Feeling like the bowel doesn't empty completely is a symptom shared by both conditions.

IBS is a chronic condition with gradual symptoms that may worsen over time, while colon cancer symptoms develop gradually over time, sometimes leading to confusion.

• The persistent and sometimes worsening nature of symptoms in IBS can mimic the progression seen in colon cancer.
• For example, someone with IBS might feel their discomfort is intensifying or that new symptoms, such as increased urgency or frequent bowel irregularities, are developing.
• Early colon cancer symptoms can be mild, often resembling IBS-related abdominal discomfort.

IBS lacks a specific diagnostic test.

• IBS is diagnosed based on symptoms and by ruling out other conditions, as there is no specific test for IBS.
• This process of elimination can sometimes delay the diagnosis of colon cancer if symptoms overlap.

The main differences between IBS and colon cancer

Why it matters: IBS symptoms are often relieved by bowel movements. In contrast, colon cancer may present with more alarming symptoms such as blood in the stool, unexplained weight loss, persistent fatigue and a change in bowel habits that doesn't improve.

IBS indicators focus on the recurrence of symptoms and symptomatic triggers after certain foods or psychological events.

• There are often long-standing patterns of abdominal pain or discomfort, typically linked to bowel movements.
• Symptoms may worsen after stress, certain foods or hormonal changes, only to improve after bowel movements.
• IBS doesn’t cause physical harm to the intestines and doesn’t lead to tissue changes or bleeding.
• Bowel habit variability is common and may result in alternating episodes of diarrhea and constipation.

Warning signs of colon cancer are typically more pronounced and include bleeding, sudden weight loss and sudden bowel changes.

• Persistent or unexplained rectal bleeding – especially if the blood is dark or tarry – should never be ignored, as it isn't typical of IBS.
• Losing weight without changes in diet or activity level can signal a more serious issue.
• Colon cancer can lead to anemia, which may cause fatigue and weakness.
• Sudden or persistent diarrhea, constipation or narrowing of stools over weeks may indicate a tumor obstructing the bowel.
• Persistent pain unrelated to bowel movements may suggest structural changes rather than functional issues like IBS.

Age can also help give context to symptoms you experience.

• IBS is more common in younger adults, especially for women, and often begins before the age of 50.
• Colon cancer, on the other hand, is more common in people over the age of 50, though cases in younger adults are increasing.

Next steps: Persistent digestive symptoms, such as abdominal pain, changes in bowel habits, blood in the stool, loss of appetite, weight loss, difficulty swallowing or severe heartburn, should never be ignored. If these symptoms last longer than two weeks, it's crucial to consult your primary care doctor without delay and request a visit to a gastroenterologist or a colon and rectal surgeon to have a colonoscopy performed. 

Get a Colonoscopy and Get Peace of Mind

Early detection makes all the difference when it comes to colorectal cancer. Either talk to your primary care physician for a referral or make an appointment with any of our gastroenterologists directly. Schedule your screening today.

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