Why are grapes toxic to dogs? Specifically, what is the toxic compound within grapes (and raisins), what is the mechanism of action that causes kidney failure in dogs, is it dose-dependent and if so, what’s the toxic dose, are all dogs equally susceptible or are some breeds or individual dogs more prone to grape/raisin toxicity, and what are the immediate and long-term treatment options for grape/raisin toxicity in canines, including supportive care and potential interventions like dialysis?

Answer

The exact mechanism of grape and raisin toxicity in dogs remains unknown, despite extensive research. However, it’s widely accepted that grapes and raisins can cause acute kidney failure in dogs.

Here are some of the details surrounding grape toxicity in dogs:

• The Toxic Agent is Unknown: Researchers have explored various potential toxins within grapes, including mycotoxins (toxins produced by fungi), pesticides, heavy metals, and tartaric acid, but no single substance has been consistently identified as the culprit. The toxic principle is likely present in the fleshy part of the grape, but the seed and skin cannot be ruled out.

• Idiosyncratic Reaction: It’s believed that some dogs are simply more susceptible to grape toxicity than others. Not all dogs that ingest grapes will develop kidney failure. The toxic dose varies significantly among individuals, making it difficult to predict the effect on any given dog. This variance suggests that the toxicity might be due to an individual dog’s metabolic or genetic predisposition.

• Kidney Damage: The primary effect of grape toxicity is acute kidney failure. This means the kidneys suddenly lose their ability to filter waste products from the blood. Signs of kidney failure include increased thirst and urination (early stages), followed by decreased urination, loss of appetite, vomiting, diarrhea, lethargy, abdominal pain, dehydration, and ultimately, coma. Histopathological findings in affected dogs show acute tubular necrosis (damage to the kidney tubules), suggesting direct damage to the renal tissues.

• Possible Involvement of Tartaric Acid and Potassium Bitartrate: A recent study suggests tartaric acid and potassium bitartrate might be a component in grape toxicity. This is however not confirmed.

• No Dose-Response Relationship Clearly Defined: There isn’t a clear-cut dose-response relationship established for grape toxicity. Meaning, there isn’t a certain amount of grapes per kilogram of body weight that is guaranteed to be toxic. Even small amounts of grapes or raisins can cause severe kidney failure in susceptible dogs.

• All Types of Grapes Are Potentially Toxic: Green, red, purple, and processed grapes (raisins, sultanas, currants) have all been implicated in cases of toxicity. Organic and non-organic grapes appear equally hazardous.

• Treatment: If a dog ingests grapes or raisins, immediate veterinary intervention is crucial. Treatment typically involves inducing vomiting (if the ingestion was recent), administering activated charcoal to absorb any remaining toxins in the gastrointestinal tract, and providing intravenous fluids to support kidney function and flush out any absorbed toxins. Blood work is essential to monitor kidney values and electrolyte balance.

• Ongoing Research: Research into the specific toxic agent in grapes continues, with scientists exploring different avenues to identify the underlying cause of this serious condition.