Dogs frequently vomit bile, and unless the condition becomes chronic, there is usually nothing to worry about. Bile is formed in the liver and secreted into the intestine, where it aids in the digestion of fats. Because vomiting empties the contents of the stomach and small intestine, the bile will be visible in the vomitus, especially if no food is present.
If the dog is vomiting bile, the vomitus will contain a bright, almost fluorescent yellow liquid. Mucus or white foam may also be present. Unlike regurgitation, where undigested food is present, the dog will not try to eat vomit containing bile, as it is very acidic.
The fact that the dog vomited bile simply means that he vomited on an empty stomach. The problem is the vomiting itself, which can have many causes. Vomiting that occurs regularly is usually a case of too much excitement, and infrequent, sporadic vomiting usually means that the dog ate something it shouldn't have. If the vomiting is frequent and irregular, it could be caused by an underlying illness. Thyroid issues, kidney or liver failure, gastrointestinal disorders and inner ear infections can all cause vomiting, and if the dog is unvaccinated, distemper and parvovirus are also a concern.
Treatment depends upon the particular cause, and the vet will run a series of tests to discover what that is. Vomiting from excitement usually involves behavioural modification, and in rare cases, sedatives. Cases stemming from eating something improper usually resolve themselves as long as no bowel obstruction is present, but if a more serious disease is the cause, more intensive treatment is needed. In many cases, the vet will withhold food for 24 hours to mitigate the irritation and dehydration caused by the vomiting itself, and to prevent the regurgitation of medication. The dog's diet will often be temporarily switched to a bland food, and reintroduced slowly.
In cases of mild vomiting, the prognosis is good, and most dogs make a full recovery. When an illness is to blame, however, the outcome depends upon the specific cause and the effectiveness of the treatment. Because vomiting is a symptom rather than a disease, it will stop as the disease is treated. In some cases, a permanent diet change is necessary to prevent recurrence.
All dogs vomit, and there is no way to prevent it. However, some careful attention can limit the frequency with which it happens. First, keep your dog current on his vaccinations. This eliminates the possibility of distemper, parvovirus or coronavirus. Second, make sure your dog does not have access to garbage, and keep small objects off the floor. Some dogs are like vacuum cleaners, and will swallow anything they can find, which can lead to major medical bills. Feed your dog a quality diet, and stay on top of his health with regular checkups and routine blood work. This way, you can catch a problem before it develops into something serious.