What type of visual examination does a sigmoidoscopy provide?

A sigmoidoscopy is a diagnostic procedure specifically designed for the direct visualization of the anus, rectum, and sigmoid colon. This examination allows healthcare providers to assess and diagnose conditions affecting these areas of the lower gastrointestinal tract, such as inflammatory bowel disease, polyps, or other abnormalities. During the procedure, a flexible tube with a light and camera at its end is inserted into the rectum, enabling a clear and detailed view of these specific segments.

The other options describe broader or different scopes of examination. For instance, visualizing the entire gastrointestinal tract would involve a full colonoscopy rather than a sigmoidoscopy, which is confined to a shorter segment. Additionally, visualization limited to the descending colon falls outside the focus of a sigmoidoscopy since it does not extend beyond the sigmoid colon. Lastly, direct visualization only of the stomach pertains to an upper endoscopy (EGD), which is unrelated to the aims of a sigmoidoscopy. Thus, the specific focus of a sigmoidoscopy on the anus, rectum, and sigmoid colon makes the correct answer a precise choice.