Grapes are certainly a popular fruit here in America (both as a fruit and the fermented juice variety) and while this is a healthy snack for people, kidney failure is associated with eating grapes and raisins in dogs. Any type of grape or raisin, as well as pulp from wine pressings, can pose a hazard.
What causes grapes to be dangerous?
All breeds of dogs are susceptible to grape and raisin toxicosis. Ingestion of as few as 4-5 raisins can be dangerous depending upon your dog's size and other factors. Grapes/raisins induce acute renal (kidney) failure by an unknown cause—frustrating, I know. Several theories exist including fungal, pesticide, and heavy metal toxins, but none have been proven. It appears from recent unpublished data that the toxic component is water-soluble, and within the flesh of the grape or raisin, not the seed itself.
Are cats affected too?
Good question, and if you learn the answer, let the vet world know! Most cats will not readily eat grapes or raisins, but we don't know if cats are susceptible to grape/raisin toxicity. To be safe, keep them away from cats for now.
What are the clinical signs?
Dogs may develop vomiting, with or without diarrhea, within the first 6-8 hours following ingestion. Your dog may also be extra jittery initially. It won't be long before the vomiting is closely followed by a decrease in that energy overload and a lack of appetite. Affected dogs may drink and urinate more. As the disease progresses, the kidneys may stop producing urine, and death can result.
What sort of tests would my vet want to do?
Diagnosis of grape or raisin poisoning is based on a history or evidence of ingestion and consistent clinical signs. While there are no specific tests available to confirm grape or raisin poisoning, basic laboratory tests reveal abnormal kidney function. Evidence of grapes or raisins may be found in the vomit or stool.
What is the treatment?
Ingestion of grapes or raisins should be considered a medical emergency and treated immediately! If you know your pet ate grapes or raisins, talk to your vet. If you have an idea of how many your dog ate, we can do some calculations and see if your pooch is in danger.
Veterinarians may recommend vomiting be induced if the ingestion was recent - within the last four hours. Activated charcoal may be given by mouth to bind with the material and prevent absorption into the body. Furthermore, your vet will likely carry out a treatment plan consisting of the following:
Baseline blood work and urinalysis to evaluate extent of renal damage
IV fluid diuresis
Monitoring of urine production
Treatment for GI ulcers with GI protectants
Careful observation for clinical signs of fluid overload such as nasal discharge, increased respiration rate, coughing, peripheral edema (swelling of the extremities)
Careful daily monitoring of blood gases, electrolytes, kidney blood tests, and urine output
Stimulating urine production if needed
Your vet will keep a close eye on your pet for 3-4 days to watch for any changes in kidney function that warrant further treatment. In severe cases, your veterinarian may recommend referral to a specialty facility for dialysis treatment.
After your dog is sent home, laboratory tests are repeated periodically to monitor the recovery of kidney function. Monitoring may be required for days to weeks as kidney function returns to normal. If chronic kidney failure develops, long-term monitoring is usually needed.
What is the outcome if my dog ate grapes?
If treated early, dogs with no clinical signs have a good prognosis. If treatment is delayed or if evidence of kidney failure develops, then the prognosis is uncertain. Recovery of kidney function may take days to weeks, and in some dogs it sadly never returns to normal.
What about grape juice or grape seed extract?
The problem is we don't know what the toxic principle is at this time, and therefore we don't know if the toxic agent is heat stabile or not. While most commercial grape juice is pasteurized, there is no way I would give my dog grape juice.
There is no known toxicity associated with grape seed extract but until we know more about grapes and raisins, I don't see enough of a compelling reason to give it to my pets.
Interestingly enough...
Not every dog (or cat) is susceptible - many animals can tolerate large quantities of grapes or raisins without problems. Nobody knows what the patient’s risk factors are (other than ingestion). Until we learn more hard facts about this mysterious fruit, simply keep it away from both your dogs and cats or be prepared for your veterinarian to answer your grape questions with more questions.