Ultrasonographic determination, in vitro and in vivo, of canine gallbladder volume, using four volumetric formulas and stepwise-regression models.

Twelve resected canine gallbladders (in vitro) and the gallbladder in each of 14 dogs (in vivo) were ultrasonographically examined. Gallbladder volume was calculated from ultrasonographically measured geometric dimensions, using 4 volumetric model formulas: cone, ellipse, biplanar ellipse, and prolate ellipse. Calculated volume was compared with true gallbladder volume, as measured by water displacement. All examined models for calculation of gallbladder volume were closely associated with true gallbladder volume (P < 0.005), and all models provided accurate predictions of true gallbladder volume (r2 > 0.80). Calculated volumes can be corrected mathematically by use of the regression coefficient and constant for each model. Body weight was not significantly associated with gallbladder volume in any of the models considered. Use of ultrasonography to accurately measure gallbladder volume could be combined with synthetic cholecystokinin-stimulated gallbladder emptying to provide information about biliary function and patency in icteric animals. Such information could aid the clinical decision between surgical or medical treatment. Correction of calculated volumes would not be necessary in association with induced emptying studies, because volume change is more important than absolute volume.