Sigmoidoscopy in Pune A sigmoidoscopy is a diagnostic test used to check the sigmoid colon, which is the lower part of your colon or large intestine. This section of your colon is close to your rectum and anus. A sigmoidoscopy can help diagnose the following symptoms: Diarrhea. Belly pain. What is a sigmoidoscopy test used for? Cancer screening Sigmoidoscopy is used to screen for colon cancer or polyps that can lead to cancer. The U.S. Preventive Services Task Force recommends a first screening at age 45. People with a higher risk of colon cancer may have a first test at age 40. Is sigmoidoscopy painful or not? The procedure isn't painful, though you may feel some gas pain or cramping when the sigmoidoscope is advancing into your intestine. The sigmoidoscope blows carbon dioxide gas into your intestine to inflate it for better viewing. This will pass after the test.