Which type of endoscope is used for visualizing the lower part of the large intestine?

The best choice for visualizing the lower part of the large intestine is the sigmoidoscope. This specific type of endoscope is designed to examine the sigmoid colon and part of the rectum, making it ideal for assessing conditions in these lower sections of the large intestine.

While the colonoscope also examines the lower part of the large intestine, it extends further and allows for visualization of the entire colon, which includes the ascending, transverse, descending, and sigmoid sections. The gastroscope is utilized for examining the upper gastrointestinal tract, including the stomach and esophagus. The duodenoscope is specifically designed for the duodenum, part of the small intestine and would not be used for the lower part of the large intestine.

Thus, the sigmoidoscope is the correct instrument for this specific task, as it focuses on visualizing the lower section effectively, while the other options are intended for different areas of the gastrointestinal tract.