Grape and raisins – why dogs are at risk

In this article we take a look at grape and raisin toxicity in dogs, a problem we often face at this time of year. Grapes and raisins of all types have been associated with acute renal failure, a problem that in some cases can be fatal.

Posted: 15 December 2018

Grape and raisins – why dogs are at risk

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The Christmas period is a particularly risky time of year with so many food offerings containing these fruits. Mince pies, Christmas pudding, Christmas cake, Stollen bread, fruit loaf and many chutneys all contain lots of raisins. It’s therefore so important to get the message spread to avoid accidental snacking by our canine friends.

Why are raisins so dangerous?

At the moment, pathologists and clinicians don’t know why the fruit is toxic, but some of the potential reasons include;

  • Mycotoxins
  • Pesticide residues
  • Salicylate chemicals
  • Tannins

How much is too much?

Clinical experience shows that a dog is more likely to be affected when large quantities of fruit are eaten. It also appears that some individuals are more sensitive than others. Some dogs appear to tolerate small doses of the fruit without consequence whilst others can show signs of toxicity after the ingestion of just a few grapes or raisins. However, there is no sure way to predict which dogs may be more sensitive, so the advice is always to keep dogs away from foods containing these fruits.

What are the signs of toxicity?

Any animal with a history of having eaten raisins and then found to be in early, mid or advanced renal failure should be considered suffering from this form of toxicity, especially if the renal failure is unexpected. Look for some or all of the following signs.

Vomiting is the most common initial presenting sign

Within the first 24 hours, most affected dogs will show signs of vomiting.

In the following 1-2 days after eating the fruit, dogs may go on to develop;

  • Lethargy
  • Dehydration
  • Abdominal pain
  • Anorexia
  • Uraemic breath
  • Diarrhoea
  • Hypercalcaemia
  • Hyperphosphataemia
  • Azotaemia
  • Oliguria
  • Anuria

Diagnosis and treatment

When presented with a suspected grape poisoning, it’s wise to recommend a full complement of diagnostic tests such as a haematology report, a serum biochemistry profile, and a urinalysis to assess the amount of damage to the kidneys. These test results will help determine the prognosis.

Treatment options include;

  • Apomorphine - grapes and raisins can remain in the stomach for prolonged periods of time, so by inducing emesis, even several hours after being ingested, you will still be able to remove potential lethal absorption.
  • Activated charcoal – these fruits tend to be broken down and absorbed slowly in the gastro-intestinal tract. One dose of activated charcoal can help prevent absorption of the unknown nephrotoxin.
  • Intravenous-fluids – this needs to be aggressive to treat and reverse acute renal failure.
  • Monitoring – serial blood tests and urine output should be performed at regular intervals during the treatment and recovery period.
  • Peritoneal dialysis – this may be necessary in extreme cases.
  • Anti-emetics - drugs to control nausea and vomiting also help control blood pressure and maintain blood flow to the kidneys.

Even asymptomatic patients that have been adequately decontaminated should have a renal panel and electrolytes monitored for 2-3 days post-ingestion.

What is the prognosis?

Overall, the prognosis varies significantly from one individual to another. It will depend on the time before decontamination and the response to treatment. Dogs that go on to develop oliguria or anuria generally are much more of a concern and have a poorer prognosis. Fortunately around half of all dogs that eat grapes and raisins never develop any clinical signs, though in practice it’s still wise to start early treatment for all animals.

Are cats and rabbits at risk?

At present, grape and raisin poisoning has only been identified as a problem in dogs. However, since there are still many unknowns associated with this poisoning, it would be sensible to avoid feeding grapes and raisins to other animals.

Get help and advice

If you’re presented with a case this winter, don’t forget to get help and advice from the Veterinary Poisons Information Service.

The Veterinary Poisons Information Service >

If you’re not already a member then maybe it’s time you joined

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