The size and contractility of the gallbladder in infants.

The size of the gallbladder and the common bile duct as well as the contractility of the gallbladder were measured in infants under the age of 1 year. A total of 43 healthy infants were studied at their routine visit to the well-baby clinic at the ages of 6 weeks, 4 months, 8 months or 12 months. Gallbladder size was measured before and after a test meal. Fasting gallbladder size increased with the age of the infants. However, when the size was corrected for the infant's weight, no age-related variation was found. The contraction index (CI) was determined as a percentage decrement of planimetric gallbladder size from the initial size. The mean CI declined with age from 75% (+/- 27%) (mean (+/- SD)) at the age of 6 weeks to 24% (+/- 28%) at the age of 12 months. Overall CI varied from -44% to 100%. An increase in gallbladder size after the test meal was observed in 4 infants. Gallbladder volumes were also calculated, but two-dimensional measurements were regarded as more accurate in infants. A large variation was found in the size as well as in the contractility of the gallbladder in infants less than 1 year of age.