CCKAR and gallstones: In contrast, in CCK-1R(-/-) female mice, aging increased the frequency of sludge and gallstone formation significantly (χ2 = 6.258, p = 0.012), and diet was not a significant factor in this: 4 of 9 CCK-1R(-/-) female mice fed CRF-1 and 9 of 15 CCK-1R(-/-) female mice fed OA-2 had sludge and gallstone formation at 12 months of age (χ2 = 0.548, p = 0.459).