Colonoscopy vs. Sigmoidoscopy: What’s the Difference?
Colonoscopy is most used for colon cancer screening
Colonoscopy is most used for colon cancer screening
Key Takeaways
- Colorectal cancer screening can save lives.
- Start screening at age 45 if you’re at average risk.
- Colonoscopy is the most common screening test.
- Sigmoidoscopy is less common, but less invasive.
Colorectal cancer is one of the most common cancers in the United States. Also called colon cancer or rectal cancer depending on where it starts, it remains a leading cause of cancer-related death in both men and women.
The good news? Screening tests can detect colon cancer early and even prevent it.
“A screening test can find precancerous polyps in the colon or rectum that can be removed before they turn into cancer,” says Walter Coyle, MD, a gastroenterologist at Scripps Clinic and Scripps Cancer Center. “It can also help find colorectal cancer at an early stage when it is easier to treat and cure.”
Why colorectal cancer screening is so important
Screening works. Colorectal cancer incidence and death rates have declined over the past several decades, according to the American Cancer Society.
The decline has occurred mainly among adults 50 and older. This is significant because the risk for colorectal cancer increases with age and the disease is much more common after age 50.
However, cases among adults younger than 50 have increased in recent years. That rise is one reason screening guidelines now recommend starting earlier.
When should you start screening for colorectal cancer?
The American Cancer Society recommends routine colorectal cancer screening for people at average risk:
- Screening should start at age 45 and continue through age 75.
- For adults 76 to 85, screening decisions should be based on personal preferences, overall health, life expectancy and prior screening history.
- Screening may begin before age 45 for people at increased or high risk.
Who is at higher risk for colorectal cancer?
You may need earlier or more frequent screening if you have:
- A family history of colorectal cancer
- A personal history of colorectal cancer or certain types of polyps
- Inflammatory bowel disease (Crohn’s disease or ulcerative colitis)
- A family history of hereditary colorectal cancer syndromes
- A personal history of radiation to the abdomen or pelvic area
If any of these apply, talk with your doctor about the best screening plan for you.
Colonoscopy vs sigmoidoscopy: What’s the difference?
Both colonoscopy and sigmoidoscopy are visual screening exams that allow a doctor to look inside the colon using a thin, flexible tube with a camera and light.
The main difference is how much of the colon each test examines. Another difference is whether the procedure may require sedation.
What is a colonoscopy?
A colonoscopy uses a long flexible tube called a colonoscope to examine the rectum and entire colon (large intestine).
Because it views the whole colon, it is the most complete visual screening test. It can detect colorectal cancer. It can also help prevent cancer by finding and removing polyps during the procedure.
How often is a colonoscopy done?
For people at average risk with normal results, colonoscopy is typically recommended every 10 years.
Do you need sedation?
Yes. Colonoscopies typically require sedation to keep you comfortable during the procedure. Because of this, someone will need to drive you home afterward.
How do you prepare for a colonoscopy?
The colon must be completely clean so the doctor can see clearly and remove any polyps found.
Preparation usually includes:
- Avoiding solid foods the day before the procedure
- Drinking only clear liquids
- Taking a bowel prep solution to empty the colon
What is a sigmoidoscopy?
A flexible sigmoidoscopy is a less invasive procedure that looks at the rectum and the sigmoid colon (the lower part of the colon). Because it examines only the lower part of the colon, it does not evaluate the entire large intestine.
How often is sigmoidoscopy done?
If used for screening, sigmoidoscopy is typically done every five years.
Do you need sedation?
Sedation is usually not required. Most people can return to normal activities shortly after the procedure.
How is preparation different?
The bowel prep is typically less extensive than a colonoscopy because only the lower colon needs to be cleared.
Is sigmoidoscopy still used for colorectal cancer screening?
Sigmoidoscopy is not widely used for colorectal cancer screening in the U.S., compared to colonoscopy and stool-based screening tests.
However, your doctor may recommend a sigmoidoscopy to help evaluate symptoms such as:
- Abdominal pain
- Rectal bleeding
- Changes in bowel habits
- Chronic diarrhea
- Other intestinal concerns
If a pre-cancerous polyp or cancer is found, the next step is typically a follow-up colonoscopy to examine the entire colon.
What about other colorectal cancer screening tests?
In addition to colonoscopy and sigmoidoscopy, there are other recommended screening options, including:
- FIT (fecal immunochemical) yearly at-home stool test
- Stool DNA test — usually every one to three years
- CT colonography — usually every five years
Your doctor can help you choose the best screening option based on your age, risk factors, and personal preferences. The most important step is choosing a test and completing it.
Raising awareness about screening
Seven in 10 adults ages 50 to 75 are up to date with colorectal cancer screening, according to the American Cancer Society, though screening rates vary by age, group, race and ethnicity, insurance status and the type of test used. Rates are lower among adults ages 45 to 49, who became newly eligible under updated guidelines.
Many people delay screening because they are unaware that screening now begins at 45, are unsure which test to choose or feel nervous about the preparation or procedure. Research has consistently identified lack of awareness, fear, embarrassment and confusion about options as common barriers to screening.
“However, it is a small price to pay for a procedure that can be life-saving,” Dr. Coyle says.
Ready to schedule a screening?
If you’re 45 or older, talk to your doctor about colorectal cancer screening options and which test may be right for you.
Scripps offers a full range of colorectal cancer screening options — including stool-based tests and colonoscopy — with services available at clinics throughout San Diego County.