ABCB4 and gallstones: These studies identify needle-like “anhydrous” cholesterol crystals and gallstone formation as an important feature of ABCB4 KO mice [105], and these exciting findings further confirm predictions from in vitro studies of model bile with low phospholipid/bile acid ratios that are similar to the lipid composition of gallbladder bile of ABCB4 KO mice [24,106,107].