 We assumed a 40 prevalence rate of esophageal varices, and a 20 rate of large varices 2,8. To detect a 15 difference in detection rate of esophageal varices between CT and endoscopy, 95 patients would require to be studied for an alpha of 0.05 one tailed test, or alpha of 0.10 two tailed test, and beta of 0.20. 