CT DETERMINED CANINE KIDNEY AND URINE IODINE CONCENTRATIONS FOLLOWING IV ADMINISTRATION OF SODIUM DIATRIZOATE, METRIZAMIDE, IOPAMIDOL, & SODIUM IOXAGLATE

This study was performed to compare investigational urographic contrast agents with a current clinical standard (sodium diatrizoate). Following 24 hour fast and fluid deprivation, four male mongrel dogs were lightly anesthetized with xylazine and sodium pentobarbitol. The bladder was catheterized for baseline urine osmolality and urine iodine concentration. Following baseline renal CT scan, sodium diatrizoate, metrizamide, iopamidol, or sodium ioxaglate was administered as a rapid IV bolus at a dose of 500 mg. Iodine/kg bw. Sequential CT scans were began at the end of bolus injection and every 70 seconds for 12 minutes, and at 15 and 20 minutes. CT scans were performed on a Pfizer 0200FS scanner using a linearized H300 scan mode with a scan time of 30 seconds. CT number of the renal cortex and inner medulla were obtained using an “area of interest” program. CT number of the bladder urine at 10 minutes was obtained by scanning known dilutions of urine in vitro. Peak renal cortical enhancement occurred within 2 minutes of bolus injection and was not dependent on the chemical makeup of the contrast agent. Peak medullary enhancement occurred within 3 minutes of bolus injection. Peak medulla CT number following sodium diatrizoate was significantly less than that following metrizamide (P < 0.025) and iopamidol (P < 0.01). Peak medulla CT number was significantly less following sodium diatrizoate (P < 0.01), metrizamide (P < 0.01), and iopamidol (P < 0.05) than following sodium ioxaglate. Urine iodine concentrations (0–10 minutes) followed a similar pattern with significant differences as follows: sodium diatrizoate < metrizamide < iopamidol < sodium ioxaglate. We conclude the investigational agents, metrizamide, iopamidol, and sodium ioxaglate, have theoretical advantages for excretory urography. Differences in renal handling of these agents is detectable with CT scanning as differences in renal medullary enhancement as well as in differences in urine iodine concentration.