What is the primary diagnostic procedure for direct visualization of the upper GI tract and for colon cancer screening?

• A. Endoscopy; esophagogastroduodenoscopy (EGD) for the upper GI tract and colonoscopy for the colon.
• B. Barium swallow.
• C. Ultrasound.
• D. CT scan.

Answer: (A)

Direct visualization of the GI mucosa is achieved with endoscopy. For the upper GI tract, this is esophagogastroduodenoscopy (EGD), where a flexible endoscope is inserted through the mouth to inspect the esophagus, stomach, and duodenum and to obtain biopsies if needed. For the colon, a colonoscope is introduced through the rectum to visualize the entire colon; this is the standard method for colon cancer screening because it can detect polyps and allow removal or biopsy in the same procedure. Other imaging tests like a barium swallow, ultrasound, or CT scan image structures without directly viewing the mucosal lining, so they’re not the primary method for direct visualization or for colon cancer screening.