A sigmoidoscope is a medical instrument used to examine the lower part of the large intestine, specifically the sigmoid colon and rectum. It is a flexible tube equipped with a light and camera, allowing doctors to visualize the inner lining of these areas for signs of disease, inflammation, or abnormalities. During a procedure called a sigmoidoscopy, the sigmoidoscope is gently inserted into the rectum. This examination can help diagnose conditions such as colorectal cancer, inflammatory bowel disease, and polyps. It is typically performed in a doctor's office and can provide important information about a patient's digestive health.