Grape and raisin poisonings in Dogs

Recently, there was a letter in the AVMA Journal from Dr. Gwaltney-Brant and others at the ASPCA Animal
Poison Control Center discussing grape and raisin poisoning in dogs. Apparently, grapes and raisins can
be toxic to dogs when ingested in large quantities.

The grapes and raisins came from varied sources, including being eaten off the vine directly. The dogs
exhibited gastrointestinal signs including vomiting and diarrhea and then signs of kidney failure with an
onset of severe kidney signs starting about 24 hours after ingestion of the grapes or raisins. The amount
of grapes eaten varied between 9oz. and 2 lbs., which worked out to be between 0.41 and 1.1 oz/kg of
body weight. Two dogs died directly from the toxicity, three were euthanized due to poor response to
treatment and five dogs lived. Due to the severity of the signs and the potential for death, the veterinarians
at the poison control center advocate aggressive treatment for any dogs suggested of ingesting excessive
amounts of grapes or raisins, including inducing vomiting, stomach lavage (stomach pumping) and
administration of activated charcoal, followed by intravenous fluid therapy for at least 48 hours or as
indicated based on the results of blood tests for kidney damage.

I have fed my dogs a few grapes every now and then for years, so I don't think there is a need to panic if a
dog eats three or four grapes but if the whole bunch is missing from the table one day, it would be good to
think about watching for any signs of a toxic reaction.

Michael Richards, DVM
Are Grapes Toxic
to your Dog?
It has recently been confirmed that grapes and raisins can cause acute renal failure in
dogs. The exact mechanism is not known, nor any means to determine the
susceptibility of an individual dog. However one vet [1] believes it may be an acute
auto-immune response to plant-borne viruses [2] in the same manner as FIP in cats.
While as little as one raisin can be fatal to a susceptible ten pound dog, many other
dogs have eaten as much as a pound of grapes or raisins at a time without ill effects.
The dog usually vomits a few hours after consumption and begins showing signs of
renal failure three to five days later.

Read Below for More information and the opinions of 2 vets

Are raisins toxic to my pet?

Within the last couple of years, the Animal Poison Control Center (APCC) in Urbana, IL has documented
multiple cases of grape and raisin poisoning in dogs. Presumably, this has occurred for years, but sporadic
cases seen by individual veterinarians have probably been discounted and written off to some other cause
of renal problems. By documentation of cases in their database, the APCC was able to establish a
correlation between renal problems and grape or raisin ingestion by dogs.

The source of the problem has been varied. Red, Concord or white grapes obtained in grocery stores or
home-grown have all been implicated. Raisins typically are made from Thompson seedless white grapes.
Other possible types of raisins are probably also toxic, but haven't been named in case reports. Chocolate
covered raisins should also be considered potential renal toxicants.

The toxic principle in either grapes or raisins is unknown. Tannins are present primarily in grape peels. The
peels are still a part of raisins. However, only low to moderate amounts of tannins are present in grapes or
raisins compared to acorns, a known renal toxicant in large animals. Whether or not tannins or their
metabolites are involved in grape/raisin toxicosis in dogs is unknown. Grapes or raisins lack significant
amounts of vitamin D, which is another recognized renal toxicant. It is unlikely that a pesticide residue is
associated with the toxicosis because of the variety of types of grapes and sources of grapes involved.
Since the toxic principles is unknown, the mechanism of action is also unknown.

So far, the vast majority of grape and raisin toxicosis have been in dogs. Based on APCC calls, the
minimum toxic dose of grapes in dogs is approximately 0.3 oz/kg body weight. This would correspond to
about most of their water content. The minimum toxic dose of raisins is approximately 0.1 oz/kg body
weight. This would correspond to about 6 raisins/kg body weight. Feeding grapes or raisins to cats or
ferrets should also be discouraged because the APCC has received a few calls of similar poisonings in
these species.

Onset of clinical signs is usually within 6-24 hours after ingestion with 12 hours being about average. Initial
clinical signs are typically GI followed by renal problems. Vomiting is usually the initial clinical sign. Other
potential clinical signs include diarrhea, depression-lethargy, anorexia, colic, dehydration and
oliguria/anuria. The course of the toxicosis may last from several days to 3 weeks. Dogs that have renal
problems have a guarded to poor prognosis.

Diagnosis is made by a history of recent exposure and compatible clinical signs. Renal clinical pathology
indices are increased. Typically, serum has increased levels of BUN, creatinine, phosphohrus and
potassium. Sometimes calcium is also increased in the serum. The urine will have hyaline casts and will be
either hyposthenuric or isosthenuric (S.G. 1.006-1.010).

Treatment is based on alleviating further absorption, if appropriate, and maintaining urine excretion and
electrolyte balance. If grapes or raisins have been ingested in toxic amounts within the last 2.3 hours, an
emetic may be used followed by activated charcoal combined with an osmotic cathartic. The animal should
be given isotonic saline IV at twice the maintenance rate for 48 hours. Metoclopramide, furosemide,
dopamine or peritoneal dialysis may be needed for some cases.

Dennis J. Blodgett, D.V.M., Ph.D
VA-MD Regional College of Veterinary Medicine
Blacksburg, VA
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