A critical evaluation of real-time ultrasonography for the study of gallbladder volume and contraction

Abstract Methods for investigating the physiology of the gallbladder in intact man are generally limited by their inconvenience and hazards, which include repeated exposure of the patient to radiation, nasoduodenal intubation, and complicated or time-consuming chemical techniques. We have carefully evaluated real-time ultrasonography for measuring gallbladder volume and contraction. We determined the validity and accuracy of ultrasound in assessing gallbladder volume and emptying in response to a stimulus. Gallbladder volume, calculated from sonography by a method which assumes gallbladder volume is equal to the sum of a series of cylinders, was 0.95 (SD = 0.01) times the true volume of bile instilled into a human gallbladder in vitro. With a rubber balloon model, containing small volumes (3–17 ml), the true volumes were overestimated by ~17% (0.5–3.1 ml). The intra- and interobserver variation in measurement of gallbladder size was usually within 10%. In 16 subjects we compared the fasting gallbladder volumes and response to a standard liquid meal on 2 successive days. The coefficients of variation in fasting volume, maximum percent emptied after meal-stimulated contraction, residual volume, and rate constant of emptying were 15.0, 12.8, 25.3, and 23.8%, respectively. In 15 consecutive subjects gallbladder volume was determined simultaneously by oral cholecystography and by real-time ultrasonography. Using the sum of cylinders technique, ultrasound volumes were 1.03 (SD = 0.11) times the cholecystogram volumes. We conclude that real-time ultrasonography is a simple, accurate, noninvasive and potentially valuable means of studying gallbladder size and emptying in intact man.