Intravenous urography using mixtures of radiopaque agents.

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In recent years increasing efforts have been made to produce intravenous urograms that rival retrograde films. Since some of the organic iodides differ in their mode of excretion, it seemed reasonable that combinations of two radiopaque agents might produce a higher concentration of iodide in the urine without an increase in the total amount of medium injected. Diodrast and Neo-Iopax were selected, since their mechanisms of excretion are entirely different. Most of the Neo-Iopax reaches the urine by glomerular filtration, as Smith (16, 18) demonstrated in 2 patients. In the usual dosage, most of the Diodrast (about 70 per cent) is secreted by the convoluted tubules and only 30 per cent by filtration, although for a few minutes after injection filtration is higher, depending directly on the plasma levels. At first the Diodrast and Neo-Iopax were injected at different times in separate syringes, but after suitable tests it was found that the contrast substances could be safely combined in the same syringe. Thirty consecutive adult pyelograms were obtained with 15 c.c. of 35 per cent Dio-drast mixed with 15 c.c. of 50 per cent Neo-Iopax, injected slowly over a five- to six-minute period. The films were compared with numerous others obtained by exactly the same technic with 30 c.c. of 35 per cent Diodrast or 30 c.c. of 50 per cent Neo-Iopax. A slight but definite increase in density of the roentgen shadow was noted when the mixture of the two iodides was used. Another advantage of the mixture, besides the increase in x-ray density, has also become apparent. It has proved to be safe and to cause very few minimal side-reactions, less than are observed with the unmixed individual drugs. Mild arm pain (vein cramps) still resulted, undoubtedly due to the Neo-Iopax. Nausea and a sensation of warmth occurred in a mild degree. No severe reactions such as vomiting, syncope, or urticaria were produced. At present, higher concentrations and larger amounts of one or both drugs are being used to determine which produces the greatest increase in density with the minimum of side-reactions. Even these large quantities can be given slowly without producing severe arm cramps. If 50 per cent Neo-Iopax is used alone, it is usually injected rapidly to avoid vein irritation. With the mixtures, this is no longer necessary. It is felt that a slow injection will reduce the incidence of severe shock-like complications, although there is no definite proof for this statement. Routine rapid injections are not necessary, even though some workers have claimed an increase in urine concentration by this method (14). Fairly severe reactions have occurred with rapid injections of 50 c.c. of 70 per cent Urokon (3). Barry and Rose (2) observed two extremely severe shock reactions in a series of 1,160 rapid injections of 25 c.c. of 70 per cent Urokon and still another was recorded by Porporis et al. (11), while Zink (20) had one among 350 cases.