Proctoscopy is a common medical procedure in which an instrument called a Proctoscope (also known as a Rectoscope, although the latter may be a bit longer) is used to examine the anal cavity, rectum or sigmoid colon.
Colonoscopy is a test that allows your doctor to look at the inner lining of your large intestine (Rectum and Colon). He or she uses a thin, flexible tube called a Colonoscope to look at the colon, A Colonoscopy helps find ulcers, colon polyps, tumors, and areas of inflammation or bleeding
The Sigmoid Colon is the final portion of the bowel that is joined to the rectum. A Sigmoidoscope is a small tube with an attached light source about the thickness of your finger, A doctor or nurse inserts the Sigmoidoscope into the anus and pushes it slowly into the rectum and Sigmoid Colon. This allows the doctor or nurse to see the lining of the Rectum and Sigmoid Colon.