Gallbladder sludge during total parenteral nutrition may be related to abnormal gallbladder motility. To test this hypothesis, gallbladder motility was assessed in 15 parenterally fed patients and in 22 controls using ultrasonography. Parenteral infusion was continuous in 10 cases and cyclic in 5 cases (6 PM to 10 AM). Gallbladder was simulated to a cone and gallbladder volume was calculated after ultrasonographic measurement of the greatest length and diameter. Six to 12 gallbladder volume measurements were performed between 8 AM and 11 PM in the parenteral nutrition group. In controls gallbladder volume was measured hourly between 8 AM and 8 PM. Thus maximal diurnal gallbladder volume and maximal diurnal gallbladder emptying, expressed as a percentage of maximum gallbladder volume, were determined. Maximal gallbladder volume was identical in the two groups. Gallbladder emptying was significantly reduced in parenterally fed patients (p less than 10(-9)) during both continuous and cyclic infusion.