A visualization of an image data record of an organ enclosing a cavity, in particular a CT image data record of a colon, that is reliable and has a low level of computational complexity, is performed according to a method. In at least one embodiment of the method a virtual viewer position outside the organ tissue is defined; an interface between the organ tissue and the cavity is defined with the aid of the image data record; from the middle of the cavity local gradients, that specify the rise in the absorption behavior between a gas contained in the cavity and the organ tissue, are determined; starting from the viewer position, a search beam is defined and an angle between the search beam and the gradients is determined; and a transparency value is allocated to the organ tissue as a function of the angle during visualization.