[Gaining insight--visualization of the invisible in urology: on the history of the technique and evidence in urological endoscopy].

The tactile inspection of the bladder had a long tradition in urology. Examination results and their interpretation depended heavily on the individual tactile skills of the urologist. Because this examination method (if correctly applied) proved the artistic skills and experience of a doctor, urologists did not see any need to replace tactile examinations with a competing method.Nevertheless, urology as well as many other medical disciplines was receptive to techniques aiming at the visualization of pathology. Visualizations served the purposes of science-oriented medicine to be objective and to document examination results. However, it needed the development of specific technologies to create objective images. One major problem in urology was the question of how to light body cavities. After extracorporeal light sources had proven to be ineffective, attempts were made at bringing light sources into the interior of the body. It needed heated tungsten filaments and later mignon bulbs at the tip of endoscopes to illuminate the bladder to such an extent that images from the interior of the bladder could be produced. The paper examines the status of these images as self-evident and objective. It is argued that the images produced were not self-evident. It is shown how combinations of texts and images were needed to develop an endoscopic viewing technique in order to read endoscopic images properly and to recognize those aspects of endoscopic documentations which were necessary for correct interpretations of the images.