Gallstones are rare in dogs. They consist mostly of calcium bilirubinate and/or cholesterol, and are therefore usually radiolucent.
Gallstones may enter the common bile duct and occlude it to cause extrahepatic and bile duct rupture. The signs are usually those of extrahepatic cholestasis from obstruction of the common bile duct.
Sometimes more acute signs of epigastric pain and vomiting are evident. Occasionally, secondary cholangitis or cholecystitis results in perforation. Gallstones are, however, often asymptomatic.
Gallstones are best diagnosed by ultrasonography and, if clinically significant, should be removed surgically rather than dissolved medically.