Shih Tzu dogs will vomit yellow bile if they have bilious vomiting syndrome, according to PetMD. This happens when stomach bile inters the intestines from the stomach in the wrong way which causes the dogs' digestion to become irritable, thus making the dog vomit up the bile.
Stomach bile is important to the functions of the digestive system including digesting food, and removing waste, notes PetMD. It is a substance formed in the liver, which is then sent to the gallbladder where it is stored until food is ingested. Once food has been ingested, the bile moves to the small intestine where it aids in digesting food so the body can use it appropriately.
Vomiting of bile is mainly seen when the dog eats, which is typically in the morning or late at night, and is most common in dogs only fed once a day. This could be due to longer periods between meals, or related to the stomach being inactive which provokes bile reflux.
Both male and female dogs are equally affected by bilious vomiting syndrome. Although is does occur mainly in older aged dogs, it can occur at all ages. If your dog is vomiting bile, then it should be taken to a veterinarian for proper diagnosis and treatment.