Urographic Contrast Agents

Urographic contrast agents are contrast agents which possess the characteristics of very little enteral absotp-tion, almost no protein binding or uptake into cells, an extracellular (interstitial) distribution and glomerular filtration. These pharmacokinetics are due to very little interaction with the organism, resulting in very low toxicity, preferably nonionic (neutral) molecules. 

Fig. 36.5a,b. DECT for the evaluation of hematuria, a Axial weighted average DECT image in the urographic phase shows contrast agent in the left renal collecting system arrows) in a 63-year-old male imaged for evaluation of hematuria, b In the... 

High Osmolality Contrast Media. An important advance in radiopaques came with the synthesis of aminotriiodoben2oic acid and its acetylated derivative, acetrizoic acid [85-36-9] (5) (8,9). Aqueous solutions of sodium acetrizoate possessed the thermal stabiUty so that they could be autoclaved (10) with minimal decomposition. The higher iodine content, ie, 3 atoms/molecule, increased the contrast efficiency, and the clinical safety of acetrizoate was improved over that of the earlier urographic agents. 

In humans the allergic reactions from contrast media resemble those elicited by histamine injection, and the unpleasant side effects are rarer after fast injection than after slow injection of the same dose of contrast medium (489). Seidel et al. (724) showed that usual doses of chemically different contrast media were able to affect the plasma histamine levels in venous blood of healthy persons. Histamine release ceases when the dose rate is reduced to 0.17 g kg min This may explain the advantage of administering urographic agents by infusion to avoid reactions. 

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