Doctors can diagnose proctitis by looking inside the rectum with a proctoscope or a sigmoidoscope. Also, air may be injected through the proctoscope to help make viewing easier. A proctoscope is another instrument that is used to visualise the rectum. The proctoscope also has a hollow channel through which other instruments may be inserted. The proctoscope is inserted into the anal canal with the patient in Sims' position.