Colonoscopy is a method we frequently use especially in the diagnosis and treatment of blood in faeces and rectal disorders. It is a method in which the large intestine is examined from the rectum with a camera under anaesthesia and lesions such as polyps are removed during the procedure. Polyps are precursor lesions, located especially in the large intestine, that occur as a result of the change of normal cells, sometimes as a precursor of cancer. With colonoscopic polypectomy, polyps are cleaned and microscopically examined by pathologists and evaluated for cancer. Special diet and medication should be used before the colonoscopy procedure. Especially for patients with kidney disease, it is more appropriate to perform these preparations in a hospital environment.