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Ask the Expert: Colon Cancer Signs, Symptoms and Screening

Dr. Douglas Purdy, gastroenterologist with St. Luke’s Gastroenterology, shares what you need to know about colon cancer signs, symptoms and screening.

What is colon cancer and how does it start?

Colon cancer is a malignant tumor of the lower gastrointestinal tract. It starts as a small, benign pre-cancerous polyp. Polyps can be as small as a millimeter in size and can slowly develop into colon cancer overtime.

What are common colon cancer symptoms people should watch for?

Symptoms can vary and many people may not have symptoms until the disease is in an advanced stage, which is why screening is vital. However, if you experience rectal bleeding, changes in bowel habits or persistent abdominal pain, talk to your doctor.

Why is the colonoscopy the gold standard in colon cancer screening?

Colonoscopies are unique in that we can not only find colon cancers, but we can prevent colon cancers as well. When performing the procedure, if we find a pre-cancerous polyp in an early stage, we can remove it, which prevents it from turning into colon cancer. Other methods of screening, such as a FIT Test or Cologuard, can miss a significant percentage of cancers and polyps. This is why you should schedule your colonoscopy as soon as you are eligible.

Is it true that colon cancer is becoming more common in younger people?

We’ve always thought of colon cancer as a disease of older people, but over the past several years, we’ve noticed people under 50 are developing colon cancer a lot more often. In people over 50, incidence of colon cancer over the past several years has been decreasing about two to three percent a year. However, over the same period of time, the incidence in patients younger than 50, specifically in the 45-50 age group, has increased by two percent a year.

Hear From Our Experts

Colon Cancer Screening


Dr. Douglas Purdy, gastroenterologist at St. Luke’s Gastroenterology, joins Dr. Arnold to discuss colon cancer signs and symptoms, the importance of screening, how to reduce your risk and more.


What are common risk factors, and how can people reduce their risk?

I like to group risk factors into two groups: modifiable and non-modifiable. You can’t do much about non-modifiable risk factors, which include age and family history of colon polyps. African Americans are at a higher risk, as well as those with type 2 diabetes, ulcerative colitis and Crohn’s disease.

Modifiable risk factors are things we can control, including sedentary lifestyle, obesity, diets low in dietary fiber and high in red or processed meats, smoking and moderate to heavy alcohol use. Staying active, eating healthy and reducing or eliminating tobacco and alcohol can greatly reduce your risk for colon cancer.

How can readers schedule their colonoscopy appointment?

If you are 45 years or older, talk to your doctor today about colon cancer screening. If you’ve been diagnosed with colon cancer or any type of cancer, call the Nassif Community Cancer Center at (319) 558-4876 or visit

Douglas Purdy

Douglas Purdy, MD, is a physician at UnityPoint Health – St. Luke’s Gastroenterology and is a practicing physician at the Helen G. Nassif Community Cancer Center.

He graduated from medical school at Southern Illinois University and completed his residency in internal medicine at the Southern Illinois University School of Medicine. He completed his fellowship in Gastroenterology at Ohio State University College of Medicine. Dr. Purdy is board certified by the American Board of Internal Medicine.


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