The visualization of the gallbladder for diagnostic purposes was made possible through the observation of Abel and Rowntree1 that halogen compounds of phenolphthalein are excreted almost wholly by the liver. Application of this principle to cholecystography was first made by Graham and Cole,2 who found that by injecting intravenously tetraiodophenolphthalein and tetrabromphenolphthalein the gallbladder could be rendered opaque to roentgen rays and therefore visible.
Tetra-iodophenolphthalein was first condemned by Graham and Cole as being too toxic for clinical use; probably they employed an impure product. Observations from this laboratory, however, have shown that with a more purified salt the toxicity of both compounds is the same. But since the opacity to roentgen rays of sodium tetra-iodophenolphthalein is twice as great as that of tetrabromphenolphthalein a good shadow of the gallbladder can be obtained by a dose only one-half as large. This means that the iodin salt is practically only one-half