Endoscopy vs. colonoscopy: Which test is best for bowel cancer screening?

In this article, a consultant gastroenterologist and endoscopist outlines the differences between endoscopy and colonoscopy, explains how they work, and helps you understand which might be the most suitable option for bowel cancer detection.

What is endoscopy?

Endoscopy is a general term for a procedure in which a thin, flexible tube with a camera is used to examine the inside of the digestive tract. There are different types of endoscopy depending on which part of the gut is being examined.

• Upper endoscopy (gastroscopy) looks at the oesophagus, stomach, and first part of the small intestine.
• Lower endoscopy can include sigmoidoscopy, which examines the rectum and lower colon.

Endoscopy allows doctors to spot abnormal tissue, inflammation, and early signs of cancer. It is usually done under mild sedation and typically takes less than 30 minutes. One of the main advantages is that small tissue samples (biopsies) can be taken for testing without major discomfort.

What is colonoscopy?

Colonoscopy is a type of endoscopy that specifically examines the entire large bowel, from the rectum to the caecum. It is considered the gold standard for bowel cancer screening because it allows doctors to both detect and remove polyps (small growths that can develop into cancer over time).

What to expect

A colonoscopy usually requires bowel preparation, where you follow a clear liquid diet and take a laxative to empty the bowel. The procedure is typically performed under sedation and can last between 30 and 60 minutes.

Benefits of colonoscopy

• Complete examination of the colon.
• Ability to remove polyps immediately.
• High accuracy in detecting early bowel cancer.

Differences between endoscopy and colonoscopy

While both endoscopy and colonoscopy are important for detecting bowel cancer, they differ in the following areas.

Area examined

Endoscopy can look at either the upper or lower digestive tract, depending on the type of procedure. Colonoscopy examines the entire colon and rectum, making it the most comprehensive test for bowel cancer.

Cancer detection

While endoscopy can detect abnormalities in the areas examined, colonoscopy is far more accurate for bowel cancer screening because it allows a full inspection of the colon and removal of potentially pre-cancerous polyps.

Preparation and sedation

Most endoscopy procedures require minimal preparation, whereas colonoscopy needs thorough bowel cleansing. Sedation is usually mild for endoscopy and mild to moderate for colonoscopy.

Biopsy and treatment

Both procedures allow biopsies, but colonoscopy has the added benefit of removing polyps during the same procedure, reducing future cancer risk.

Which test is right for you?

For most people at average risk of bowel cancer, colonoscopy is preferred if a full examination of the colon is needed. Sigmoidoscopy or other forms of lower endoscopy may be offered in certain screening programmes, or if only the lower bowel requires evaluation. Upper endoscopy is rarely used for bowel cancer screening, but may be important if you have symptoms affecting the upper digestive tract.

A specialist gastroenterologist will guide you based on your age, family history, and any previous findings such as polyps or inflammatory bowel disease.

Both endoscopy and colonoscopy are valuable tools in detecting bowel cancer early, but they serve different purposes. Understanding the differences helps you make an informed decision, ensuring that any potential issues are detected and treated as early as possible.