Which diagnostic procedure provides direct visualization of the colon for cancer screening?

• A. Endoscopy
• B. Capsule endoscopy
• C. Ultrasound
• D. Colonoscopy

Answer: (D)

Direct visualization of the colon for cancer screening is achieved with colonoscopy. A flexible instrument is inserted through the rectum and advanced through the entire colon, allowing the clinician to view the mucosal lining in real time, identify polyps or suspicious lesions, and perform biopsies or remove polyps during the same procedure. The other options visualize different parts or aspects of the GI tract: endoscopy targets the upper GI tract, capsule endoscopy uses a swallowed camera to survey the small intestine, and ultrasound images tissues with sound waves rather than directly inspecting the colon lining. Because it both visualizes the colon and enables immediate intervention (polyp removal or biopsy), colonoscopy is the preferred method for colorectal cancer screening.