Determinants of gallbladder kinetics in obesity.

Obese subjects are at risk of developing gallstones both by being overweight and by reducing their body weight. The aim of the present study was to investigate factors related to disturbances in gallbladder emptying measured by ultrasound. Detailed information about weight loss attempts, age at onset of obesity, parity, presence of menopause, use of contraceptive or hormonal replacement drugs, and phase of menstrual cycle was obtained. Smoking habits, alcohol use, dietary intake, and physical activity were recorded. Body composition and fat distribution were assessed by anthropometry. Blood samples were taken for CCK, lipids, glucose, and insulin. Mean (SD) fasting gallbladder volume was 30.0 (12.6) ml. The residual volume was 12.5 (9.8) ml 90 min after a test meal. CCK levels increased from a basal 1.64 (0.8) pM to a peak value of 2.9 (1.0) pM. Fasting gallbladder volumes were closely related to residual and ejection volumes. Body weight and fasting insulin levels explained 35.2% of the variance in fasting volume, lean body mass and insulin explained 28.1% of the residual volume, and waist circumference 23.6% of the ejection volume. None of the other factors were related to gallbladder emptying. Subjects with the largest fasting gallbladders had the largest residual and least emptying gallbladders, scored the highest in every aspect of body size, composition, and fat distribution, and also had the highest insulin levels. Body weight, lean body mass, central fat distribution, and insulin levels were the main determinants of gallbladder kinetics. Fasting and residual gallbladder volumes were closely related and both determined by obesity and its metabolic complication of hyperinsulinemia.