Review article: gall-bladder motor function in obesity.

A number of epidemiological studies has established obesity as a risk factor for gallstone disease. More recently, studies have suggested a relationship between gallstone disease and the metabolic syndrome linked to central adiposity, whose cardinal feature is represented by hyperinsulinaemia. Studies on fasting gall-bladder volume in obese subjects show that this parameter correlates with weight, body mass index (BMI) and body surface area; however, this is also true for large-sized non-obese subjects. Gall-bladder volume also correlates with abdominal fat and with impaired glucose tolerance. In contrast to the well-established role of bile supersaturation in the pathogenesis of gallstones in obesity, data are controversial on whether gall-bladder motor function is defective in obese subjects. However, studies were heterogeneous for subjects' BMI, emptying stimulus, technique used and parameters assessed to evaluate gall-bladder motor function. Also, differences in baseline gall-bladder volume may lead to wide differences in bile 'washout' effect despite apparently similar percentage changes in volume or content. Although post-prandial plasma levels of cholecystokinin (CCK) are normal in obese subjects, there is some evidence that a sub-group of obese subjects could have decreased sensitivity to CCK, possibly mediated by hyperinsulinaemia. Further studies using standard physiological stimuli and controlling for glucose tolerance, fasting insulin levels and baseline gall-bladder volume are needed to establish the role of gall-bladder motor function in the pathogenesis of gallstone disease in obesity.