Which procedure involves visual examination of the sigmoid colon by endoscopy?

• A. Thoracentesis
• B. Pulmonary Angiography
• C. Sodium Levels
• D. Sigmoidoscopy

Answer: (D)

The main idea is performing an endoscopic look at a portion of the large intestine to inspect its inner lining. When the target is the distal colon, specifically the sigmoid region, the procedure is called sigmoidoscopy. It uses a flexible scope inserted through the rectum to view the sigmoid colon (and sometimes the lower rectum) to check for abnormalities such as polyps, inflammation, ulcers, or bleeding. This differs from the other options, which are not endoscopic examinations of the sigmoid colon: thoracentesis samples fluid from the chest, pulmonary angiography images the blood vessels of the lungs, and checking sodium levels is a laboratory test.