Ask the Vet: Why Do Dogs Vomit Undigested Food?

Dr. Ivana Crnec

When dogs vomit undigested food, dog owners are often concerned considering that the dog risks not obtaining many nutrients especially if the vomiting takes place quite often. An accurate diagnosis is therefore important to ensure the dog doesn't suffer any negative repercussions from such repeated vomiting. Following is information about dogs vomiting undigested food from veterinarian Dr. Ivana Crnec.

We all know that our canine babies are overzealous eaters. They eat in large quantities and sometimes they can even eat non-edible things. These feeding indiscretions are, more often than not, followed by vomiting. In such cases, the vomiting is a useful defense mechanism – the goal is to eliminate the gastric content that is making trouble.

From the above stated, it can be concluded that sometimes vomiting is useful. But how to know in which cases the vomiting is expected and useful and in which cases it is considered a red flag? Generally speaking, the vomiting is considered a red flag and requires further examination if it occurs too often and if the vomiting content includes undigested food. 

How Dogs Digest Food

 The digestion of food in dogs occurs on multiple layers. In the mouth each mouthful of food is prepared for digestion by being grinded by the teeth and softened by the powerful enzymes in the saliva.

 Once the food has been chewed and broken up, it is swallowed and enters the esophagus. In the esophagus, the waves of muscular contractions push the food toward the stomach even against the forces of gravity.

 At the top of the stomach, a tight ring of muscle called the cardiac sphincter opens to allow food in. At the other end of the stomach, another ring of muscle, called the pyloric sphincter, opens at intervals to allow food to pass into the intestines.

 In the stomach, the food mixes with hydrochloric acid and starts breaking down. The muscular waves in the stomach mix and move the food thus contributing to its breakdown. Then, the digested food is passed into the intestines where digestion is completed and the molecular components of food are absorbed.

Dog Vomiting Versus Regurgitation

When the food from the esophagus is almost effortlessly and without retching expelled through the mouth, we are talking about regurgitation. When food that has passed through the esophagus into the stomach is forcefully brought up with the help of muscular contractions we are talking about vomiting. 

Plus, while regurgitation occurs almost immediately after eating and without any signs of distress, vomiting occurs some time after eating and it is almost always announced by signs of distress such as drooling, retching and lip-smacking.

Knowing the difference between vomiting and regurgitation is of paramount importance. Additionally, it is important to know whether vomiting comes on suddenly or slowly and if it is persistent or intermittent.

When a dog regurgitates, the expelled content is undigested food. On the other hand, when a dog vomits, the content can be either digested or undigested food. 

Why Do Dogs Vomit Undigested Food?

Regurgitation occurs almost immediately after eating and it can occur due to a wide range of underlying causes such as: a dog eating too fast, feeling excited while eating, and eating immediately after exercise.

Esophageal problems, may too be a cause as it may happen with foreign bodies in the esophagus, strictures in the esophagus, inflammation of the esophagus

 Megaesophagus, a condition manifested with an enlarged esophagus due to the decreased ability of its muscle layer to control the tone and diameter, which ultimately, leads to the esophagus losing its ability to efficiently push the food into the stomach, can too be a trigger as so are esophageal tumors.

Throwing up undigested food hours after eating is indicative of abnormal emptying of the stomach contents into the intestines. The most common underlying causes include: blockages, ingesting poisonous substances and motility issues that slow down the digestion time. 

What Happens at the Vet?

In most cases, if your dog vomits undigested food, it is wise to contact your vet the same day so that the cause of the vomiting can be diagnosed and treated.

When presented with a dog who vomits undigested food, the vet will perform several diagnostic procedures such as:

Physical examination – in all but the fattest dogs, a vet can feel the intestines and the stomach through the abdominal wall. Physical examination can reveal the consistency of the gastrointestinal contents and show the presence of any obstructions or signs of constipation.

X-rays – plain x-rays are useful when a dog is vomiting and suffering from diarrhea or abdominal pain or if the vet can feel an abnormality. They may reveal gas, foreign bodies, masses and obstructions. Barium contrast x-rays (in which barium, a material opaque to x-rays is used to define the different structures of the digestive tract) are useful for showing defects and observing the passage of food.

Ultrasound – ultrasound scanning reveals masses and can visualize enlarged lymph nodes. It is also useful for calculating the thickness of the wall of stomach and intestines.

Endoscopy – the use of a flexible viewing tube is ideal for looking in the stomach and first part of the small intestines (via an endoscope passed through the esophagus and stomach) or the last part of the large intestines (via an endoscope passed through the anus). Endoscopic biopsies (the removal of tissue samples via instruments passed through down an endoscope) are also useful when diagnosing gastrointestinal issues manifested with vomiting.

Laboratory tests – blood tests and biochemistry panels give a good indication of how well the process of digesting food goes on. 

Treatment For Dogs Vomiting Undigested Food

The course of the treatment depends on the cause for vomiting undigested food.  Mild cases of vomiting undigested food can be treated with simple diet changes. 

Based on the cause and severity of the vomiting, as well as on the age and fitness of the dog, it is advisable to withhold food for 4-24 hours after the vomiting stops. Meanwhile, you can offer your dog small, but frequent amounts of water. To ensure proper hydration it is recommended to use electrolyte solutions formulated specifically for dogs. 

When reintroducing food, keep the food choices simple and avoid overeating – offer small meals but frequently. The ideal meal for troubled stomach consists of one part low-fat cottage cheese with two parts boiled rice.

In more severe cases, keeping the vomiting dog hydrated requires administering intravenous fluids. In such cases, it is also important to use anti-vomiting drugs such as metoclopramide. By controlling the vomiting, you manage the loss of fluids and create conditions suitable for stabilizing the irritated stomach.

Ultimately, in some cases, correcting the underlying cause requires surgery. In those cases, the dog is hospitalized and subdued to proper intravenous fluids, antibiotics and proper pain management. 

About the Author

Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia.

She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.

Ivana’s research has been published in international journals, and she regularly attends international veterinary conferences.

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