Effect of CCK-8 dose levels on gall bladder ejection fraction (GBEF) in 'abnormal' gall bladders

Full text: There is no current consensus on the optimum dose of cholecystokinin (CCK) in hepatobiliary scanning. Two common protocols incorporate 3 minute injection of CCK-8, either 0.01 mcg/kg or 0.02 mcg/kg. For both abnormal GBEF is <35%. Both have been validated empirically. This study examined whether these protocols are equivalent in the clinical setting. Methods: 43 patients received Tc-DIDA IV. At 60 minutes CCK-8 was injected over three minutes: 01 mcg/kg in group A (n=30) and 02 mcg/kg in group B (n=13). GBEF was calculated over 20 minutes. If GBEF was <35% a second injection of CCK was given (group A 0.02 mcg/kg, group B 0.01 mcg/kg ) and GBEF re-calculated. It has been shown previously that serial CCK doses are equivalent to doses administered separately. Results: Group A: nine patients (30%) had GBEF >35% with 0.01; nine (30%) had GBEF <35% with both 0.01 and 0.02; 12 (40%) had abnormal GBEF with 0.01 but normal GBEF with 0.02. Group B: five (39%) had GBEF >35% with 0.02; five (39%) had GBEF <35% with both 0.01 and 0.02; 3 (22'%) had abnormal GBEF with 0.01 but normal GBEF with 0.02. For patients with initial GBEF <35% as a group no predictive relationship was found for GBEF determined using the 2 CCK doses. However, examination of individual patient responses suggests a complex relationship. Conclusion: These 2 CCK-8 doses do not give equivalent results in gallbladder scintigraphy. This has obvious clinical implications. It suggests variability between individuals in the CCK-8 responsiveness of different components of the biliary system. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc