Penning et al’s paper is a brain-teaser (see page 264). It clearly shows is that, in the laboratory, the gall bladder behaves abnormally in patients with chronic constipation. What is much less clear, but very intriguing, is what the findings mean. Recently, the state of the gall bladder in patients with constipation has been attracting attention because of growing evidence that cholesterol gallstones can result from slow intestinal transit.1-3 Slow transit allows the colon to absorb excessive amounts of bacterially degraded substances, including the toxic bile acid, deoxycholic acid (DCA). When DCA reaches the liver, it makes it secrete more cholesterol into bile and when it reaches the gall bladder it hastens the crystallisation of cholesterol.2 ,4 So, patients with slow transit constipation should be at high risk of gallstones. Puzzle number one is that the patients in Penning et al’s study seem to have escaped gallstones (although this is not …