Recently, veterinarians discovered that grapes, raisins and currants (fruits from Vitis species) can cause kidney failure in dogs.
Poisoning has occurred in dogs following ingestion of seedless or seeded grape varieties, commercial or homegrown fruits, red or green grapes/raisins, organic or non-organic fruits, and grape pressings from wineries. Foods containing grapes, raisins, and currants (such as raisin bran cereal, trail mix, granola mix, baked goods) are all potential sources of poison.
Unfortunately, there is no well-established toxic dose for any of these fruits but two principles seem to prevail: 1) Dogs are more likely to become poisoned if they ingest large amounts of fruit and, 2) there is significant individual sensitivity amongst dogs. Some dogs appear to tolerate small doses of the fruit without consequence while other dogs may develop poisoning after the ingestion of just a few grapes or raisins. There is no way to predict which dogs may be more sensitive.
Some researchers suspect that a mycotoxin (a toxic substance produced by a fungus or mold) may be the cause. Some suspect a salicylate (aspirin-like) drug may be naturally found in the grape, resulting in decreased blood flow to the kidneys. However, so far no toxic agent has been identified.
The most common early symptom of grape or raisin toxicity is vomiting, which is generally seen within 24 hours following ingestion. Lack of appetite, lethargy, and possibly diarrhea can be also seen within the next 12-24 hours. More severe signs are not seen for 24-48 hours after ingestion – often after acute kidney failure has already begun. Signs of acute kidney failure include nausea, lack of appetite, vomiting, uremic breath, diarrhea, abdominal pain, excessive thirst, and excessive urination.
The best treatment is to decontaminate a patient right away via the induction of vomiting and administration of activated charcoal. Following decontamination, more treatment might be necessary including aggressive intravenous fluids to flush any absorbed toxins out of the body as quickly as possible and to help maintain kidney function. Dogs need to be hospitalized on intravenous fluids for 24 to 48 hours following ingestion.
If a dog only ate a few grapes or raisins (depending on the size of the patient) and received immediate treatment, the prognosis is excellent.
Onions, garlic, alcohol, chocolate, cocoa, macadamia nuts, fattening foods, and foods containing the sweetener xylitol can also be fatal.