A colonoscopy is a medical procedure used to examine the inside of the large intestine (colon and rectum), typically performed by a gastroenterologist.

From a gastroenterologist’s point of view, it’s one of the most important tools for both prevention and diagnosis of gastrointestinal disease.

What is a colonoscopy?

A colonoscopy involves inserting a thin, flexible tube with a camera (called a colonoscope) through the rectum to visualize the entire colon. The camera transmits real-time images, allowing the physician to closely inspect the lining of the bowel.

Why is a colonoscopy done?

Gastroenterologists use colonoscopy to:

• Screen for colorectal cancer (this is the gold standard screening tool)

• Detect and remove polyps (small growths that can become cancerous over time)

• Investigate symptoms like:

  • Rectal bleeding

  • Chronic diarrhea or constipation

  • Abdominal pain

  • Unexplained anemia

• Diagnose conditions such as:

  • Inflammatory bowel disease (IBD) (Crohn’s, ulcerative colitis)

  • Diverticulosis/diverticulitis

  • Colorectal tumors or strictures

What makes a colonoscopy an important procedure?

• It’s both diagnostic and therapeutic — meaning we can find issues and treat them during the same procedure (e.g., remove polyps, take biopsies).

• It allows direct visualization, which is far more accurate than imaging alone.

• It can prevent cancer, not just detect it early, by removing precancerous polyps.

What can patients expect from a colonoscopy?

• Done under sedation, so patients are comfortable and typically don’t remember the procedure

• Usually takes 20–45 minutes

• Requires a bowel prep beforehand to clean out the colon for clear visibility

​

From a GI standpoint, colonoscopy isn’t just a test—it’s a preventative, life-saving intervention that plays a central role in maintaining long-term digestive health.