The efficacy of ultrasound-guided cholagogue-induced gallbladder emptying for differentiating obstructive from non-obstructive hepatobiliary diseases was studied in icteric dogs. In 7 healthy Beagle dogs, Lipofundin 20% infusion (2 ml/kg orally) evoked a vigorous gallbladder contraction of 44.2% (range: 35.3–57.6%) and proved to be a useful, well-tolerable meal for routine use. In 24 icteric dogs, gallbladder contraction was evoked by different cholagogues: the maximum reduction in gallbladder volume (%) for the three non-obstructive icteric dogs was 43.9% (range, 39.0–46.5%). The average gallbladder contraction of the 21 dogs with biliary obstruction was less than 5%. In conclusion, the stimulation of gallbladder contraction with orally applied magnesium sulphate (MgSO4) or Lipofundin can be well demonstrated by ultrasound in dogs. The examination of cholagogue-induced gallbladder emptying is a valuable technique in icteric patients to indicate surgical intervention.