Quantitative cholescintigraphy: selection of random dose for CCK-33 and reproducibility of abnormal results

Dynamic cholescintigraphy (DCG) is a valid technique for evaluating gallbladder emptying. Cholecystokinin (CCK) as a slow infusion is recommended as a contraction stimulus. The normal ejection fraction (EF) has been shown to be reproducible, although the reproducibility of abnormal results has not been investigated. The aims of the present study were to standardize the CCK administration method (phase 1), obtain EF normality values (phase 2), and evaluate the reproducibility of abnormal results in patients with clinically suspected gallbladder dysfunction (phase 3).

Phase 1 included 40 healthy volunteers divided into 4 groups (n = 10) and subjected to intravenous CCK infusion according to 4 different regimens (0.25, 0.30, 0.40, and 0.60 Ivy dog units [IDU]/kg). Phase 2 comprised 33 healthy volunteers for determining DCG normality values, and phase 3 evaluated the reproducibility of abnormal results in 44 patients having clinical manifestations compatible with gallbladder dysfunction and showing an abnormal EF in a previous study.

The most effective CCK infusion regimen was 0.40 IDU/kg (3.07 ng/kg) over 20 min, because it afforded the least variability and a high EF. When this regimen was applied to the healthy population, the EF was found to be 74.2% +/- 17.1% (mean +/- SD); the inferior normality limit was estimated to be 40%. Abnormal results were recorded in 77% (95% confidence interval, 62%-89%) of the patients. When the 2 DCG studies of phase 3 were compared, the EF correlation coefficient between them was 0.439 (P = 0.003).

Slow CCK infusion is the best regimen for stimulating gallbladder contraction; an EF of less than 40% is estimated to represent abnormality. The abnormal results for the EF in patients with clinically suspected gallbladder dysfunction proved to be reproducible.