The need for more study of gastrointestinal contrast media.

After four score years of alimentary tract radiology based on barium sulfate, we have little agreement on the proper characteristics of the contrast agent for visualization of the esophagus, stomach, duodenum, and colon, nor have we had any viable replacements, organic or inorganic, for barium sulfate. A number of characteristics of barium sulfate preparations have been examined. A positive charge on the particle is not of advantage in mucosal coating, but viscosity seems to be important. Particle size is probably not important. Suspension stability is probably overrated. Much, if not most, of the properties of barium sulfate preparations depend on the surface active agents, the so-called additives. The thickness of barium sulfate coating necessary for surface visualization under clinical conditions is defined. Some preliminary data on a new barium preparation is reported.