Sequential changes in the CT numbers of the normal canine kidney following intravenous contrast administration. II: The renal medulla.

Following the intravenous administration of sodium and meglumine salts of both diatrizoate and iothalamate (at doses of 310-880 mg I/kg body weight) sequential changes in computed tomographic (CT) numbers of the inner medulla were determined in three dogs, using a 30-second CT scanner. Peak medullary enhancement was greater than, and usually occurred 1-2 minutes after, peak cortical enhancement. The CT number of the medulla increased linearly with increasingly large doses of the contrast agent. At peak enhancement, the meglumine salts produced a significantly lower (p less than 0.025) mean CT attenuation value of the medulla than did the sodium salts. The difference in mean attenuation values between the sodium salts and meglumine salts was maximum (50-60 HU)at peak enhancement. Our data indicate the known difference in renal handling of the meglumine and sodium salts is readily detectable by CT.