Background: Sonographic diagnosis of acute cholecystitis remains equivocal at times. The variance of gallbladder ejection fraction may be useful in diagnosis. This study evaluated the ejection fraction difference between cholecystitis patients and a control group, and also determined the diagnostic cutoff level. Patients and Methods: Twenty patients with a diagnosis of acute cholecystitis, subsequently confirmed by pathologic findings after cholecystectomy, and 20 control patients with asymptomatic gallbladder stones were included in this study. A commercial formula, 475 Kcal with 43% lipids, was used for the test meal. All subjects received serial sonography to analyze gallbladder volume and ejection fraction before and 15, 30, 45 and 60 minutes after the test meal. Results: Before the test meal, the mean gallbladder volume of the cholecystitis group was larger than that of the control group (54.5 mL vs. 20.1 mL, p=0.002). The cholecystitis group had significantly lower ejection fraction than the control group at all time points after the test meal (15 minutes, -7.8% vs. 48.4%; 30 minutes, -0.9% vs. 65.8%; 45 minutes, 6.5% vs. 62.7%; 60 minutes, 6.6% vs. 71.4%; p<0.001). Using 40% ejection fraction as the cutoff level, patients with cholecystitis could be differentiated entirely from the control group at 45 or 60 minutes after the test meal. Conclusion: Patients with acute cholecystitis have bigger gallbladder volume before a meal and lower ejection fraction after a fatty meal, compared with controls. From 45 to 60 minutes after a fatty meal, 40% ejection fraction can be used as the cutoff level to differentiate patients with acute cholecystitis from those who do not.
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