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Background: Chronic Acalculous Symptomatic hyPERkinetic (CASPER) gallbladder is a novel clinical condition. Criteria for diagnosis include biliary symptoms in the absence of gallstones but with a high gallbladder ejection fraction on cholescintigraphy (HIDA scan). Most studies use an ejection fraction above 80% as a cut-off for a gallbladder hyperkinesia diagnosis, but variations in cholescintigraphy methodology can affect the reading. Here, we report a previously undescribed effect where longer fasting times diminish the ejection fraction in gallbladder hyperkinesia patients, that could be explained by presumable gallbladder overdistention that impedes contraction.

Methods: We report a retrospective series of 7 patients whose clinical presentation was suspicious for symptomatic gallbladder hyperkinesia, based on 12 most common symptoms and signs of gallbladder hyperkinesia that we previously identified, but whose gallbladder ejection fraction was less than 80%. We recognized that these 7 patients had all been fasted overnight prior to cholescintigraphy. We therefore repeated cholescintigraphy with only 4 to 6 hours of fasting.

Results: The repeat cholescintigraphy showed a 94% increase in mean ejection fraction from 46.5% to 90.3% when fasting time was shorter, compared to initial cholescintigraphy done with overnight fasting (Paired t-test, p = 0.0017). Six of the 7 patients opted for cholecystectomy and showed substantial symptom improvement and abnormal pathologic findings. One patient with manageable symptoms opted for medical management with dietary control.

Conclusions: Gallbladder ejection fractions from cholescintigraphy done after overnight fasting are diminished and thus misrepresent gallbladder contractility in gallbladder hyperkinesia patients. Cholescintigraphy using shorter fasting times provides more consistent data on gallbladder contractility in these cases. National guidelines for cholescintigraphy need redefinition, especially in the context of gallbladder hyperkinesia.