Elizabeth Kingston

Measurement of Gallbladder Emptying Sequentially Using a Single Dose of 99mTc-Labeled Hepatobiliary Agent

The gallbladder emptying response to a single large (20 ng/kg) and four equally divided sequential small (5 ng/kg each) doses of octapeptide of cholecystokinin at 20-min intervals was measured in a paired study in six normal subjects noninvasively and quantitatively by a nongeometric method using a gamma camera, computer, and 99mTc-labeled hepatobiliary agent. The gallbladder mean (+/- SD) ejection fraction after a single large dose (20 ng/kg) of octapeptide of cholecystokinin was 34 +/- 24% and after four sequential small (5 ng/kg each) doses was 42 +/- 14%, 45 +/- 28%, 37 +/- 22%, and 32 +/- 27%, respectively (p greater than 0.05). The results of this study indicate that the first part of the 5 ng/kg sequential octapeptide of cholecystokinin dose is as effective as the single 20-ng/kg dose. The gallbladder emptying requires continued presence of high levels of octapeptide of cholecystokinin in the serum closer to levels that initiate contraction and in the absence of which the gallbladder ceases to empty further despite the fact it has inherent capacity to do so. Each of four equal octapeptide of cholecystokinin doses given sequentially elicits, on the average, an equal degree of emptying response. The method has potential for application in the study of the pharmacological effects of drugs on the biliary dynamics using a single dose of 99mTc-labeled hepatobiliary radiopharmaceutical.

Comparison of biokinetics and biliary imaging parameters of four Tc-99m iminodiacetic acid derivatives in normal subjects.

The biokinetics (blood clearance, urinary excretion, hepatic peak time, uptake, and excretion t-½) and the imaging parameters (the time of appearance of the common bile duct, gallbladder, and duodenum) were determined in 34 normal subjects using Tc-99m diethyl (EIDA), Tc-99m dimethyl (HIDA), Tc-99m paraisopropyl (PIPIDA), and Tc-99m parabutyl (PBIDA) iminodiacetic acid derivatives. The blood and hepatic clearance of the four agents were significantly different (P < 0.05) from each other. The 24-hour urinary excretion of PBIDA was significantly lower (P < 0.05) than the urinary excretion of the other three agents. There was no difference among the four agents in the time of appearance of the gallbladder and duodenum. The time of appearance of the common bile duct was significantly delayed with PBIDA. The maximum intensity of the common bile duct usually occurred between 20 to 40 minutes with all four agents. However, gallbladder intensity continued to increase up to 3 hours. It is concluded that in the presence of normal liver function, all four Tc-99m IDA agents show definite differences in biokinetics but these differences do not have a major effect on biliary imaging parameters. If imaging alone is the primary goal, the selection of any one of the four agents will meet the clinicians need satisfactorily.