Abstract: Process for maintaining the cleanliness of the inner cavity of a medical operating instrument (I), particularly a surgical instrument used in minimally invasive medicine, having an outer casing (M) and operating or actuating elements (SS, SH) arranged therein, said instrument being used to enter the body of a living person or animal, wherein during its use the instrument is acted upon essentially from its proximal end through a fluid connection (A) with a medically clean fluid (G) in such a way that essentially all the crevices and cavities in the inner space, in fluid contact with the inside of the body, between the operating or actuating elements (SS, SH) or between the latter and the casing (M) are filled with the fluid.