What causes yellow vomit in dogs?
Intestinal problems, usually involving vomiting, are some of the most common reasons for consultation at veterinary clinics. More often than not it is because the patient has eaten a foreign object that causes irritation in the stomach or intestines and in 89% of cases the signs resolve spontaneously in under 2 days, as indicated in a study published in The Journal of Small Practice1. Yellow vomit is less common, although it is often very worrying for owners and is sometimes indicative of a more serious pathology.
The most common cause of yellow vomit in dogs: bilious vomiting syndrome
In most cases, yellow vomit in dogs simply indicates that they have an empty stomach. The yellowish colour is due to the presence of bile, a digestive fluid produced in the liver and stored in the gallbladder before being released into the small intestine.
Food stimulates gallbladder contraction, which empties part of its contents. On the contrary, fasting facilitates filling of the gallbladder and consequently the gallbladder absorbs most of the water in the bile which becomes more concentrated.
Whenever the stomach is empty, duodenal–gastric reflux is more likely to occur in the gastric lumen, causing bile to irritate the mucosa and induce vomiting, which normally has a foamy appearance due to the mucus in the stomach. This is known as bilious vomiting syndrome.
A sudden change in diet involving an increase in the time between meals can cause this type of vomiting. Indeed it is more frequent in the morning, when the dog has not eaten for hours. However, the side effects of medications or stress can also cause yellow vomit in dogs. A diet based exclusively on a low-quality feed with many chemical additives can also compromise the dog’s gastric health and trigger this vomiting.
Medical problems associated with yellow vomit in dogs
A study conducted at Colorado State University2 in 17 dogs with yellow vomit revealed that 12 had bilious vomiting syndrome and improved with treatment, but three cases were diagnosed as having gastric adenocarcinoma, dietary indiscretion and liver disease. In fact, other causes of yellow vomit that should be considered during the differential diagnosis are:
- Gastrointestinal disorders. Yellow vomit can be a sign of other problems that affect the digestive system, such as inflammatory diseases, ulcers, parasitic infections and even some types of cancer. For example, gastritis, an inflammation of the stomach lining which is quite common in dogs, can cause vomiting and stomach acidity, in which case the vomiting usually occurs a few hours after eating.
- Bowel obstruction. Toys, bones or any other object that the animal has ingested may cause bowel obstruction. In these cases, the vomit becomes bilious once a series of regular vomiting episodes have emptied the stomach. This clinical picture is accompanied by an extreme lack of energy and intense abdominal pain.
- Allergies. Dogs that consume anything to which they are allergic may produce yellow vomit. This usually occurs after a change in the diet. The products most likely to cause an allergy are dairy products, wheat, maize, soya, fish, lamb and pork.
- Pancreatitis. Whenever the pancreas is inflamed, it releases enzymes and other substances that trigger localised inflammation with potentially fatal outcomes in the most acute cases. In addition to vomiting, the clinical picture is usually accompanied by fever, dehydration, anorexia, diarrhoea and abdominal pain. If the pancreatitis is due to the patient consuming fatty foods, the vomiting may occur 24–48 hours after consumption.
- Liver disease.The liver plays an important role in various metabolic processes, so any impairment of its function is usually reflected in the digestive, nervous and renal systems. In some cases, yellow vomit in dogs is accompanied by diarrhoea, acholic faeces due to obstruction of the bile ducts and coagulation disorders.
In cases of bilious vomiting, the clinical signs usually improve if the patient follows an easy-to-digest, low-fat and high-fibre diet such as the Advance Veterinary Diets Gastroenteric. It is also important to feed dogs with smaller but more frequent rations spread out over the course of the day.