Cats vomiting: what’s normal, what isn’t

Cats vomiting is not unusual, but it can also be a sign of disease so cat owners need to know what’s normal and what isn’t.   When it occurs more than two times a month, if the frequency is increasing, or if your cat is losing weight, it needs to be investigated.

Cats vomiting: possible causes

There are many causes of cats vomiting. Sometimes it is a diet intolerance that can be diagnosed with a change in food or a formal food trial with a hypoallergenic diet. Cats that eat grass or other hard-to-digest plants will frequently vomit. Cats may vomit up hairballs from time to time. However, sometimes vomiting it is due to a more serious disease that needs to be diagnosed and treated specifically.

Diagnostic tests

There are many diagnostic tests that can be performed to establish the causes of frequent vomiting. Some are blood tests, and some involve taking x-rays with or without barium. The most useful test for most cats is an ultrasound of the stomach and small intestine. Increased thickness of the stomach or small intestinal wall is the most significant finding. If thickening is found, there are two primary possible diagnoses: inflammatory bowel disease (IBD) and cancer, although about 5% of the time another disease will be found.

The only way to diagnose either is by obtaining biopsy samples of the small intestinal wall, usually by performing abdominal surgery. With that sample, a veterinary pathologist can determine if IBD or lymphoma is present and can classify the type of each. This information is needed to make a treatment plan and determine the prognosis.

Inflammatory bowel disease

When the small bowel wall is significantly thickened, there is about a 50% chance it will be due to IBD. This disease is caused by a chronically irritated stomach and intestinal lining. It may be caused by an irritant in the diet, or it may be just an abnormal immune system overreacting to normal food or things in the food. However, the speci c cause is not usually determined.

Inflammation interferes with digestion and absorption of nutrients. Therefore, cats with advanced disease are losing weight and often have an increase in their appetites as they attempt to make up for the weight loss. Poor motility of the thick intestines is associated with vomiting.

Treatment includes immunosuppressive drugs (usually corticosteroids), special diets, probiotics, and vitamin B12 injections. Often, cats get an initial short course of anti-parasitic drugs and antibiotics. IBD is not considered a curable disease, but proper treatment can control it and stop or slow the vomiting and weight loss. Overall, the prognosis is very good.


Lymphoma is cancer that involves lymphoid tissue. Lymphoid tissue is found in lymph nodes, the tonsils, the spleen, the stomach, and the intestine. The greatest concentration is in the small intestine, so lymphoma is common in this location. Lymphoma accounts for about 45% of the cases of intestinal wall thickening, and it occurs in two forms: small cell lymphoma and lympho blastic or large cell lymphoma. Biopsy is needed diagnose lymphoma and to distinguish between its forms.

Treatment for either form of lymphoma seeks to achieve remission, not a cure. Even in people with lymphoma, the word ‘cure’ is not used for lymphoma. The disease may be in remission for many years, and the patient may be symptom-free, but it can always return. Remission in cats means that vomiting or diarrhoea stops, their appetites return to normal, lost weight is regained, and the small intestinal wall returns to normal thickness.

Treatment for the two types of lymphoma carries different prognoses. Cats with lymphoblastic lymphoma have a lower success rate; fortunately, there are fewer cases of this type. Although many cats respond well to treatment, the prognosis is always guarded. Cats with small cell lymphoma have a much better success rate; approximately 70% to 75% will go into remission with thee average time of remission is around two years, although we have seen cats live more than four years in remission.

Is vomiting hairballs really normal for cats?

There is a common belief that the vomiting of hairballs is common and insignificant because it is normal in cats. Consequently, you might purchase diets and medications that can be used to prevent frequent vomiting of hairballs. The diets are usually high in soluble fibre that attracts fluid to itself as it goes through the digestive tract. This softer, moister stool will carry hair through the digestive tract and out with the stool. The medications are lubricants or stool softening agents that also help to move hair through the digestive tract.

Our newer understanding of hairballs questions the wisdom of using these products without first knowing if a cat has disease of the stomach or small intestine. IBD and lymphoma create a motility disorder. e thickened stomach wall and intestinal loops do not move hair through the digestive tract at its normal speed. This slower movement results in abnormal hair collection in the stomach or intestines, resulting in hair-ball formation.

Some cats, especially long-haired cats, swallow so much hair during their normal grooming process that hairballs can develop and be considered normal. However, a cat’s stomach and intestines need to be examined with ultrasound if the cat is not long-haired, the cat is a poor groomer, or vomiting of hairballs occurs more than twice a month. If they are found to be normal, a hairball diet or a hairball medication is definitely indicated.

Another important reason not to ignore hairballs is that there is mounting evidence that untreated IBD may transform into lymphoma. If a cat has IBD and that is what is causing hairball formation, delaying treatment for IBD may allow IBD to transform into cancer.

Many cats that have been vomiting for months to years are found to have lymphoma. The ultrasound study is usually performed because either weight loss becomes substantial or the frequency of vomiting increases to a troublesome level for you or your veterinarian. In reality, most of the time that vomiting was occurring the cat had IBD, but then it transformed to lymphoma. When lymphoma developed, the signs became severe enough to seek a cause.

Therefore, treating hairballs with special diets or medications may reduce vomiting and control hairballs when the underlying disease is IBD, but that is the time when the cat needs to be diagnosed and treated for IBD so it does not become lymphoma.

Information provided by Gary D. Norsworthy, DVM, DABVP (feline); Jen Olson, DVM; and Loren Gassler, DVM, Alamo Feline Health Center, San Antonio, Texas. – DVM


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