CLAIM

The ingestion of raisins or grapes can produce acute renal failure in dogs.

Mixture

RATING

Mixture

WHAT'S TRUE

Many anecdotal reports link the development of acute renal failure in dogs after those canines ingested grapes or raisins.

WHAT'S FALSE

Many dogs can ingest grapes or raisins with no harmful effects, and the putative mechanism behind the consumption of grapes and raisins resulting in acute renal failure in canines is unknown.

ORIGIN

A sad tale about raisin toxicity in dogs began circulating on the Internet in April 2004:

WARNING Dog Owners

This week I had the first case in history of raisin toxicity ever seen at MedVet. My patient was a 56 pound,5 yr old male neutered lab mix who ate half a canister of raisins sometime between 7:30 AM and 4:30 PM on Tuesday. He started with vomiting, diarrhea and shaking about 1 AM on Wednesday but the owner didn’t call my emergency service until 7 AM.

I had heard somewhere about raisins AND grapes causing acute renal failure but hadn’t seen any formal paper on the subject. We had her bring the dog in immediately. In the meantime, I called the ER service at MedVet, and the doctor there was like me—had heard something about it, but…. Anyway, we contacted the ASPCA National Animal Poison Control Center and they said to give I V fluids at 1 1/2 times maintenance and watch the kidney values for the next 48-72 hours.

The dog’s BUN (blood urea nitrogen level) was already at 32 (normal less than 27) and creatinine over 5 (1.9 is the high end of normal). Both are monitors of kidney function in the bloodstream. We placed an I V catheter and started the fluids. Rechecked the renal values at 5 PM and the BUN was over 40 and creatinine over 7 with no urine production after a liter of fluids.

At the point I felt the dog was in acute renal failure and sent him on to MedVet for a urinary catheter to monitor urine output overnight as well as overnight care. He started vomiting again overnight at MedVet and his renal values have continued to increase daily. He produced urine when given lasix as a diuretic. He was on 3 different anti-vomiting medications and they still couldn’t control his vomiting.

Today his urine output decreased again, his BUN was over 120, his creatinine was at 10, his phosphorus was very elevated and his blood pressure, which had been staying around 150, skyrocketed to 220. He continued to vomit and the owners elected to euthanize.

This is a very sad case—great dog, great owners who had no idea raisins could be a toxin. Please alert everyone you know who has a dog of this very serious risk. Poison control said as few as 7 raisins or grapes could be toxic. Many people I know give their dogs grapes or raisins as treats. Any exposure should give rise to immediate concern. Feel free to contact me if you have any questions.

Laurinda Morris, DVM
Danville Veterinary Clinic
Danville, Ohio

Unlike many of the pieces being forwarded from one inbox to the next, this one seemingly had some truth to it.

According to the ASPCA, around 1989 a disturbing trend began to emerge from the AnTox database used by its Animal Poison Control Center: dogs reported to have eaten grapes or raisins developed acute renal (kidney) failure. The ASPCA’s Animal Poison Control Center reported receiving hundreds of calls over a three-year span regarding adverse exposure to grapes or raisins in dogs:

Dogs are exposed to grapes and raisins in many ways. Frequently, dogs will eat fruit off the vine, steal from plates, and even eat wine pressings. Grapes and raisins have been recommended
as treats and training aids because fruit is tasty and relatively low in calories. Unfortunately, dogs can have dangerous reactions to grapes and raisins. Between January 2001 and August 2004, over 200 calls were made to the ASPCA Animal Poison Control Center involving potential exposures to grapes or raisins in dogs. Sensitive dogs have a risk of initial gastrointestinal upset followed by acute renal failure (ARF).

These cases were noted all across the USA, with the amount eaten varying widely, from over a pound of grapes to as little as a single serving of raisins:

The database showed that dogs who ate the grapes and raisins typically vomited within a few hours of ingestion. Most of the time, partially digested grapes and raisins could be seen in the vomit, fecal material, or both. At this point, some dogs would stop eating (anorexia), and develop diarrhea. The dogs often became quiet and lethargic, and showed signs of abdominal pain. These clinical signs lasted for several days — sometimes even weeks.

When medical care was sought, blood chemistry panels showed consistent patterns. Hypercalcemia (elevated blood calcium levels) was frequently present, as well as elevated levels of blood urea nitrogen, creatinine and phosphorous (substances that reflect kidney function). These chemistries began to increase anywhere from 24 hours to several days after the dogs ate the fruit. As the kidney damage developed, the dogs would produce little urine. When they could no longer produce urine, death occurred. In some cases, dogs who received timely veterinary care still had to be euthanized.

That said, a good deal of mystery and uncertainty still attaches to this subject. Why grapes and raisins seemingly affect dogs but not other animals in this way, why only some dogs are susceptible, and exactly how grapes and raisins lead to renal failure are unknown. Factors such as the presence of external contaminants or toxins (such as pesticides), the ingestion of seeds, and the manner of grape cultivation don’t appear to be determinative:

In cases of grape or raisin toxicosis in dogs, the actual mechanism of action remains unknown. The exact pathophysiology of ARF following the ingestion of grapes or raisins remains undetermined. Theories include metabolic disruption, a nephrotoxic mycotoxin, and an idiosyncratic reaction. Dogs that have developed ARF were exposed in various ways. Ingestions included grapes purchased from a grocery store as well as grapes found in the backyard, grape pressings from wineries, and both the seedless and seeded varieties. Some of the grapes involved were tested for pesticides, heavy metals, and mycotoxins (all findings were negative). It is unclear if the skin of the grape must be ingested for ARF to occur. Currently, grape-seed extract is not considered a threat; only the grape or raisin itself is considered a danger. So far, dogs are the primary species affected. Whether other species are affected remains unknown.

The symptoms typically associated with grape toxicity in dogs are as follows:

o Your dog has lost his/her appetite and refuses to eat its favorite food.

o The pet is unusually still, refuses to play, go out of the house and is lethargic.

o The dog has diarrhea or starts vomiting. This will usually occur within a couple or a few hours after the dog has eaten grapes or raisins.

o The dog’s abdomen is tender when you touch it, which indicate abdominal pain.

o The dog present dehydration signs which often include a dry nose, heavy panting, and very pale gums. The easiest way to test is your dog is suffering from dehydration is to softly pull the skin on the dog’s nape of the neck, which should spring back on the spot.

Pet owners need not live in dread fear of their dog’s keeling over dead after swallowing a grape or two. However, if a canine should down a handful of grapes (or even a smaller amount of raisins), a prompt trip to the veterinarian would likely be in order. Aggressive treatment with intravenous fluids and close monitoring are a canine’s best chance for survival after the ingestion of something toxic.

Grapes and raisins aren’t the only people foods reported as dangerous to man’s best friend. Chocolate and cocoa can prove deadly to them, as can onions and macadamia nuts.

Sources:

Bowen, Jill.   “It’s Wise to Watch What Your Dog Eats.”
    Roanoke Times & World News.   25 April 2004   (p. NRV20).

Dale, Steve.   “Skip Grapes, Raisins As Laxative for Dogs.”
    The Houston Chronicle.   19 August 2003   (p. 3).

Krzeckowski, Cathy.   “Expert Finds Grapes Can Be Harmful to Some Dogs.”
    The [Bergen County] Record.   17 October 2002   (p. F5).

Means, Charlotte.   “The Wrath of Grapes.”
    ASPCA Animal Watch.   Summer 2002   (Volume 22, No. 2).

Sayler, Catherine.   “Kidney Failure and Sour Grapes.”
    Santa Fe New Mexican.   27 July 2003   (P. E6).

Whitcomb, Tiffany.   “Pets.”
    Buffalo News.   30 January 2004   (p. B22).

The Augusta Chronicle.   “Grapes Are a Dangerous Treat for Pets.”
    31 July 2003   (p. D4).

McKnight, Katrina.   “Grape and Raisin Toxicity in Dogs.”
Veterinary Technician.   February 2005.

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