Iodinated Organic Compounds As Contrast Media for Radiographic Diagnoses

Abstract

In the course of testing o-(4-hydroxy-3,5-diiodobenzyl)-benzoic acid (I) as a cholecystographic agent in dogs, it was observed that the extrahepatic biliary ducts were visualized as well as the gallbladder. Since duct visualization would be a desirable addition to cholecystography, a comparison was made against the standard cholecystographic media to determine whether this property was unique with the benzoic acid derivative. Dogs were used as subjects, and comparisons were made both by oral administration and by intravenous injection. Only the new compound (I) consistently gave good visualization of the extrahepatic ducts after oral administration, Injected intravenously in the form of their sodium salts, the benzoic acid derivative (I), iodoalphionic acid (Priodax) (II), tetraiodophenolphthalein (III), and phenoltetraiodophthalein (IV), all delineated the ducts. There were marked differences, however, in the rate and degree of visualization achieved with each preparation. Delineation was most rapid with o-(4-hydroxy-3,5-diiodobenzyl)-benzoic acid, and slowest with the iodinated derivatives of phenolphthalein. The time interval for initial duct visualization was in the range of ten to forty minutes. To eliminate the effect of the gallbladder on the secretion of the cholecystographic media, a number of examinations were made on dogs both before and after cholecystectomy. Intravenous injections of the benzoic acid derivative (I) and of iodoalphionic acid (II) gave satisfactory duct delineation. Anatomy The dog is the most satisfactory of the laboratory animals for the study of chole cystographic media, and is particularly suitable for the investigation of the secretion of such media into the biliary tract. The liver of the dog is divided into five chief lobes which are separated by deep fissures and drained by three main hepatic ducts. Although in situ the lobes overlap, the fresh specimen may be spread out so that all lobes and the main parts of the extrahepatic duct system are visible, as shown in Figure 1A. The gallbladder lies in a cleft between the two parts of the right central lobe and empties into the middle hepatic duct. The duct system varies greatly from dog to dog, but usually the right hepatic duct drains into the union of the left and middle branches a short distance from the entrance of the common duct into the duodenum. On roentgenograms the biliary system is best shown in lateral views, with the animal lying on its right side. Figure 1B is a lateral roentgenogram made after the injection of the biliary tract with ethyl iodophenylundecylate emulsion (1). For this illustration 7 c.c. of bile were replaced with 8 c.c, of emulsion through the cannulated common duct of a dead dog weighing 8.2 kg. Experimental Subjects: Stock dogs in apparent good health and weighing from 6 to 25 kg. were used in the preliminary studies.