The procedure uses a special tube (speculum) introduced through the rectum to look inside the entire large intestine (the colon). This is done with a narrow, flexible instrument known as a colonoscope, measuring between 130 and 200 cm. The visual tracks in a colonoscope make it possible to present images from inside the gastrointestinal tract at an adequate magnification level on a colour monitor. The purpose of the examination is to assess the mucosal surface of the large intestine. With the use of additional instruments, it is possible to collect mucosal specimens for histopathological examination and perform endoscopic examinations which often help patients avoid surgical interventions.