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Why Is My Dog Vomiting?

Ron Hines DVM PhD 10/25/03
Many cats and dogs and ferrets are brought to my animal hospital by frowning owners because they have found a mess on the floor.

Sometimes it is a rather straightforward project deciding why the pet vomited but it can be quite difficult. Vomiting, like fever, has a myriad of causes. In this article I touch on some that come to mind.

I am always jubilant when owners actually bring me a sample of the material. Many folks can’t bear to do this but the material vomited is often the clearest indication of the cause. Material that is high in mucus tells me that the stomach or high intestine is inflamed. Undigested food can indicate food poisoning, anxiety, or simply over eating. Bile is often present when vomiting is caused by inflammatory bowel disease or pancreatitis. Flecks of bright blood tell me that the stomach is lacerated. If the blood is brown and caramelized I know that the problem is farther down the intestine. Strong digestive odors suggests intestinal obstruction. Bits of aluminum foil, Christmas tree tinsel, Big Mac wrappers, etc. tell me that this is a dietary indiscretion that will be easy to manage. Another important clue is the relationship of vomiting to the pet’s last meal.

When I examine these pets I am careful to look in their mouth for foreign bodies like bones wedged in the throat or enlarged tonsils. I check the color of their gums to be sure they are not shocky and look for the dry gums of dehydration. I take the pet’s temperature (normal dog & cat=101.5-102.5F,normal ferret=103-103.5) and carefully palpate the abdomen to detect an inflamed intestine or abdominal pain. If I develop the opinion that this is probably no more than a passing incident I limit the pets intake to clear fluids for forty eight hours and have the owners bring me collected stool samples from over this period. Many objects that initially cause vomiting are eventually passed in the stool. Vomiting can be curative in itself in that it purges spoiled food and toxins from the stomach and intestine. If I do not think the vomiting is helpful, I send these pets home with trimethobenzamide or Reglan pediatric suppositories to stop the vomission. The following list are some common and not so common causes of vomiting in dogs and cats. Within their groups, they are listed in the order that I encounter them; the most common ones first.

Causes Associated With Things Eaten:

Dietary Indiscretions

The most common cause of vomiting in dogs and ferrets (not so in cats) is dietary indiscretions – the eating of garbage, grass, plant leaves, etc. It is amazing the things pets will eat. Many of these are actually separation anxiety cases where a panicky pet eats everything in sight (see article on separation anxiety). Placing these pets on a large dose of petrolatum-based cat laxative helps slide this material out with the stool. These pets need to be monitored carefully for seventy-two hours to be sure the intestine does not block. At the first sign of abdominal distress, depression, general weakness, fever or blood in vomitus or stool, they should be taken to a veterinarian for further testing.

Diet Change

For reasons that have never been clear to me, changing a dog or cats and ferret’s diet from one brand to another often causes a few days of vomission. This problem is worse when the diet is changed to a bargain-priced generic chow high in indigestible protein, rendering plant meal and roughage but it occurs even when the change is from one name brand to another. This problem can be avoided by making the change gradually.

Eating Too Rapidly

Dogs, cats and ferrets that are not fed frequently enough or feel competition from other pet members may vomit undigested food soon after eating. Feed these pets smaller, more frequent meals and feed them in separate rooms of the house.

Intolerance to Specific Food Items

Pets love to beg at the dinner table. The fact that you seem to relish a food item makes it fair game to your pets. Hot dogs, pastrami, pizza, deviled ham and the like get wolfed down fast – but often come back up just as fast. No harm is done. These pets are not actually allergic to these foods. Dogs and cats have a very easy vomit reflex and the slightest irritation of the stomach brings these items back up. If you cannot bear to stop feeding table scraps, feed them in smaller portions. Pleasure is in the eating – not in the portion size.

Food Allergy

Veterinary textbooks speak of vomission due to food allergies but I do not recall a true case that I have encountered. Food allergies in cats and dogs generally manifest themselves as itchy skin disease. If the gastrointestinal tract is affected it is much more likely to cause diarrhea.

Disorders Of the Stomach and Small Intestine:

Obstructing objects

Anything that blocks the exit from the stomach will eventually cause vomiting.

I never cease to be amazed at what pets will eat. During my thirty-seven years of practice I have removed tennis balls, Christmas ornaments, coins, fishing gear, socks, acorns, rocks, rubber duckys, stage props, jewelry, and bones of all sizes from the stomachs of dogs and cats. Ingestion of foreign objects the most common cause of vomiting in ferrets. Most bones dissolve rapidly in gastric aids without surgery if we can manage the patients long enough. I suppose the most interesting thing I ever removed from an animal was the urethane foam “last will and testament” of Uncle Shmedley, a one thousand pound walrus used in the Sea World Kooky Castle production. Most of these objects I remove with an endoscope, a fiber optical instrument that is passed through the mouth to the stomach. If the object will not easily budge or is too far down the intestine, I remove it surgically.

Acute Gastroenteritis of Ferrets

Several bacteria cause infections of the gastrointestinal tract of ferrets that appear as bloody diarrhea, vomiting and dehydration. Stress is often the precipitating factor in these conditions. Ferrets that vomit and pass fluid stools rapidly dehydrate. Dehydration can be fatal in these pets. The first thing I do is give the ferrets large doses of intravenous and subcutaneous fluid. (5% dextrose). I place them on injectable antibiotics, keep them warm and withhold all food and oral liquids. Bacteria most often associated with this problem are salmonella, helicobacter and campylobacter. Because diarrhea and vomission remove these bacteria and their toxins from the body I rarely attempt to lessen them. Instead, I replace the fluids and nutrients as they are lost.

Inflammatory Bowel Disease of Ferrets

In this condition the lining of the stomach and small intestine becomes inflamed and may also ulcerate. Some feel that this problem is a form of autoimmune disease - others that it is due to allergies to various ingredients in a ferret diet (possibly chicken). Perhaps both can play a part. Ferrets with this condition pass frequent loose watery stools and may also vomit. They become very thin. Diagnosis of this condition is often made by elimination of other causes. Exact diagnosis can only be made from biopsies of the pet’s intestine, which may require surgery. Because these symptoms are quite similar to acute and chronic bacterial gastroenteritis of ferrets, stool samples need to be cultured for the bacteria that cause them. When these causes of similar disease have been eliminated, the ferrets usually improve on a regimen of amoxicillin, metronidazole (Flagyl) and prednisolone. This disease is rarely cured but it can be managed. I usually put these pets on Pepto-Bismol and Tagamet as well. It is hard to put weight on them because food moves too rapidly through their intestines and much of the absorptive power of the intestinal lining has been lost. This is why additional vitamins help these pets.

During flare-ups, liquid diets such as AD can be feed. Then, feeding one of the bland diets marketed for similar conditions in cats (i/d, EN, ZD, etc.) often minimizes this problem. Bland diets marked for cats have sufficient protein but those manufactured for dogs contain less than the optimal amount for ferrets. If dog products are used, I suggest that they be supplemented with vitamins, cooked egg whites and cottage cheese. Low intermittent oral doses of corticosteroids such as prednisone are also helpful.


Immature dogs and cats that have large numbers of roundworms or hookworms may vomit. These kittens and puppies usually have as large potbelly. Hookworms cause vomission by inflaming the lining of the small intestine but roundworms just block the intestine by their mechanical presence. The owners often see long spaghetti-like roundworms in the material vomited up. Hookworms are too small to see. Both these parasites are quickly and safely eliminated with oral pyrantel pamoate (2.5-10mg/lb). Stomach worms of dogs and cats exist but I have never encountered them. I have never seen hookworms or roundworms in ferrets.

Chronic gastritis

Certain cats, dogs and ferrets vomit frequently due to an inflamed stomach. Two personality types are involved. One is the animal that regularly eats objectionable objects such as dirt, gravel, feces, leaves bark and wood. Sometimes this is a response to boredom. We call this condition pica and I cannot say what is going through these pet’s minds. The second group of pets is high-strung and somewhat neurotic. They are usually thin and often have dry hair coats. They often also have bouts of diarrhea and can never tolerate changes in their diets. When I think of this condition I think of German shepherds and Siamese cats and ferrets of any age. The first group of pets has to be supervised at all times. Some veterinarians give them mega doses of B-vitamins to try to alleviate pica. The second group is best fed a very bland monotonous diet. The corticosteroid drugs, prednisone or prednisolone also helps this second group.

Gastric Dilatation-volvulus

Deep-chested breeds of dogs will occasionally have their stomach flip over on itself causing a kink at either end. When this happens, the stomach quickly over inflates with gas. These dogs try to vomit but cannot. They appear quite ill because circulation to the stomach is cut off. This is a life and death emergency. The animal rapidly goes into shock and becomes toxic. Under light sedation I pass a stomach tube into their stomachs to relive the bloat. Then I open the dogs up, replace the stomach to its proper position and sew it to the abdominal wall so it the problem can not reoccur.

Two other forms of knotting of the small intestine, volvulus and intussuception also cause vomiting. Volvulus is a spinning round of the intestine causing it to kink. Intussusception is a folding in of the intestine upon itself. In both cases food cannot pass and circulation to that portion of the bowel is interrupted. Some people call this a strangulated intestine. I correct both these problems surgically.

Tumors of the Stomach and Intestines

In old debilitated dogs, cats and ferrets vomiting can be a sign of tumors of the stomach or small intestine. These tumors can be large fleshy masses or subtle infiltration of the walls of the stomach and intestine with cancerous cells. I see more of these cases in cats and ferrets than in dogs. Often I can feel the tumor through the abdominal wall (see article on cancer in pets in this series). If I am uncertain of the diagnosis I give these pets oral barium sulfate (contrast medium) and then X-ray them periodically as the barium moves through the stomach and intestines. The contrast medium outlines the shape of tumors that would normally be invisible on X-ray. I usually make the final diagnoses by surgically opening the animal and removing samples of the stomach and intestine to be sent to a pathologist. We call this procedure an exploratory laparotomy. These tumors are usually malignant and not good candidates for surgery. I try to convince the owners to euthanize these pets - it is the least you can do to prevent suffering of an old friend.

Metabolic Disorders:

Kidney Disease And Uremia

In older pets with failing kidneys, toxic products build up in the blood stream causing depression, nausea and vomission. Earlier in uremia, pets keep their bodies cleansed of waste products by drinking and urinating excessively. Although their kidneys have lost much of their ability to concentrate wastes in the urine, the large quantities of dilute urine produced maintain their metabolic equilibrium. Eventually excessive drinking no longer suffices and blood levels of urea and creatinine reach toxic amounts at which vomiting occurs. At this stage of kidney disease, ulcers also form in the stomach and small intestine. Pets with this problem are noticeably ill. They are usually dehydrated, thin and anemic. Administering large quantities of intravenous fluids (diuresis) correct the situation for a while but eventually these pets pass away. Kidney transplantation has been performed successfully in cats to cure uremia. These are cats that suffered acute kidneys loss due to consuming antifreeze.

The procedure is much less successful in cases of chronic kidney disease where other organs have been damaged over time.

Liver Disease

Liver disease in dogs, cats and ferret is another cause of vomission. Liver damage can occurs as the result of eating poisonous products or through bacterial and viral infection. These pets are often jaundiced or yellow. Stool specimens from these animals may be light in color or deep yellow. Blood enzymes associated with liver damage are usually quite elevated. They may also show excessive thirst, weight loss, prolonged bleeding time and fluid buildup in their abdomens. Many of these pets respond to treatment and go on to live relatively normal lives and when they do vomission ceases. Some need long-term specialty bland diets to lessen the workload of the liver

Heat Stroke

Heat stroke is common in dogs with flat faces and longhaired breeds left in the sun too long in the hot summer months. Over heating is extremely common in ferrets but not in cats. These pets are giddy. Their breath is rapid and shallow and they often vomit and produce diarrhea.

They are depressed, have rapid heart rates and may collapse or have seizures. Their body temperatures can be as high as 109F. I lower their core body temperature as rapidly as I can by immersing them in ice water.

Adrenal Gland Disease

Hypoadrenocorticism or Addison’s disease is a condition in which the two adrenal glands produce insufficient cortisone. A common sign of this disease is vomiting – especially during times of stress. The most common form of this disease is probably a form of autoimmunity in which the body destroys its own tissue. Other signs of this disease are depression, diarrhea, hypoglycemia (low blood sugar), low blood pressure, muscular weakness and an increase in white blood cells called lymphocytes. Pets may drink excessively. It is a disease with very vague symptoms, which is why it is frequently misdiagnosed. The problems tends to wax and wane, appearing to be a digestive problem one time and a kidney problem another. Dogs and cats with the problem are usually between 4-8 years old. No one breed is more susceptible to the disease than another, but about 70% of pets with this problem are female.

Other Disease:

Motion Sickness

Many pets vomit when they are first taken on car rides. The best way to prevent this is to not feed them before travel. Rolling a car window down slightly to encourage a dog or cat to look out also helps. After a number of car rides the condition usually ceases. When it continues to be a problem the pet can be given Dramamine (dimenhydrinate at 2-4 mg/pound in dogs and 10 mg per cat or ferret) before travel.

Sudden inflammation of the pancreas causes frequent vomiting. Dogs presented to me with this condition are usually middle-aged and plump. Schnauzers and standard dachshunds are the most common breeds that I see affected. Often they have recently eaten a very fatty meal. I have not encountered this disease in cats or ferrets. These dogs are depressed and their tummies are tight and painful. They are often dehydrated due to vomiting. Some have diarrhea. X-rays of these pets have a hazy “ground glass” appearance characteristic of this disease and peritonitis. When I draw blood from these dogs the plasma is often very milky in color due to increased cholesterol and triglycerides in the blood. High pancreatic enzymes are the signature test for this disease. These tests for pancreatic enzymes (amylase, lipase) are quite elevated and the dogs usually have elevated kidney and liver tests as well as elevated white blood cell counts. Much of the elevation in test results is due to the profound dehydration that accompanies this disease.

My first step in treating pancreatitis is to rehydrate the dogs with intravenous fluids, stop the vomission with medications and decrease pancreatic inflammation with corticosteroids. When I have done this I withhold food and water for 3-4 days to allow the pancreas to “rest”.

Most veterinarians, including myself, place these dogs on antibiotics of the penicillin/cephalosporin class. I cannot explain the rational for this – we just do it. After 3-4 days I being them back on oral fluids and foods very slowly. Relapses months and years later are common. The best way to prevent them is to feed these pets a high carbohydrate, low fat diet.

Middle and Inner Ear Disease

Ear infections that have migrated to the inner ear affect the organs of balance and can cause vomiting. A much more common sign is head tilt to the affected side (see articles on ear infections and surgery in this series).

Physical Disorders:

Diaphragmatic hernia
Sometimes vomiting is the only sign of a tear in the diaphragm. A disrupted diaphragm can be a congenital disease that the pet was born with or it can occur as the result of a car accident. Dogs and cats with this problem tend to vomit shortly after eating. They vomit when portions of the stomach or small intestine become trapped in the tear. X-rays pick up this problem. I become suspicious of diaphragmatic hernias when a pet is reluctant to lie down and becomes agitated when its rear end is elevated higher than its shoulders. Diaphragmatic hernias are surgically repaired.