Grapes Toxicity in Dogs – far less sweet than it should be

by | Mar 31, 2022

Grapes, raisins and sultanas are healthy right?  Nice little bite sized treats?  Unfortunately, this group of fruit can cause kidney failure in our dogs, sometimes resulting in irreversible damage and even death.  Whilst the toxicity concern for all three of these sweet fruits are the same, raisins can commonly be found in combination with other foods, therefore potentially increasing the risk of exposure as compared with grapes and sultanas. Foods containing grapes, raisins, and sultanas (such as raisin bran cereal, trail mix, granola mix, baked goods etc.) are all potential sources of poison.

Unfortunately, there is no well-established toxic dose for any of these fruits but there are two principles to keep in mind:

1) Dogs are more likely to become poisoned if they ingest large amounts of this fruit and,

2) there appears to be ‘individual’ sensitivity in dogs. Some dogs appear to be able to  tolerate small doses of these fruits without consequence, whilst other dogs may develop poisoning after eating just a few grapes or raisins.

Currently, it is not known why these fruits are toxic. Over the years, there has been speculation as to whether the toxicity may be due to a mycotoxin (a toxic substance produced by a fungus or mould) or a salicylate (aspirin-like) drug that may be naturally found in the grape, resulting in decreased blood flow to the kidneys. More recently, it has been considered that tartaric acid may be the cause. However, to date, no specific toxic agent has been clearly identified. Since it is currently unknown why these fruits are toxic, any exposure should be a cause for potential concern.

If you suspect that your pet has eaten any of these fruits, contact us here at the hospital immediately.  If we are not open, any emergency centre will be willing to provide advice over the phone and will likely recommend a consultation at the very least.  Since there are still many unknowns associated with this poisoning, it is better not to take any risks when it comes to your dog’s health. As with any toxin, the sooner the poisoning is diagnosed and treated, the less dangerous it will be for your pet, and the less expensive treatment will be for you in the long run.

So, what to watch for?

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 diarrhoea 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 damage has already begun. Signs of acute kidney failure include nausea, lack of appetite, vomiting, uremic (ammonia odour) breath, diarrhoea, abdominal pain, excessive thirst, and excessive urination.  As poisoning progresses, the kidneys will stop functioning and the dog may not be able to produce urine.  Following this, the dog’s blood pressure often decreases dramatically.  The dog may lapse into a coma due to a build up of substances which the kidneys usually eliminate from the body through urine.  Once the kidneys have shut down and urine output has dropped, prognosis is very grave.

Unfortunately it is difficult to diagnose grape toxicity as the symptoms are non-specific and early signs are similar to a variety of things including simply eating foods that should not be eaten.  More severe signs are similar to kidney failure from other causes. A veterinarian will base a diagnosis of this poisoning on a history from the owner, or the presence of pieces of grapes or raisins in the dog’s vomit.

How do we treat it?

Your veterinarian will recommend diagnostic tests such as a complete blood count (CBC), a serum biochemistry profile, and a urinalysis to assess the amount of damage to the kidneys. The test results will help determine the dog’s likelihood of recovery.

The goal of treatment is to block absorption of the toxins and prevent or minimize damage to the kidneys.  The best treatment is to decontaminate the dog right away by inducing vomiting and administering activated charcoal. This helps to prevent absorption of the toxin from the stomach or intestines. As grapes and raisins stay in the stomach for a prolonged period of time, inducing vomiting is very important (even up to 4-6 hours after ingestion). Following decontamination, more treatment will likely be necessary, including aggressive intravenous fluids to help support/protect the kidneys in hopes of minimizing damage to them. Drugs used to control nausea or vomiting, to help maintain blood flow to the kidneys, and to control blood pressure may also be administered.

Ideally, dogs should be hospitalised on intravenous fluids for 48 hours following ingestion.  Affected animals may need to be hospitalised for several days.  During treatment, your veterinarian will monitor the dog’s kidney function levels daily to assess the response to treatment and determine whether the treatment needs to become more aggressive.  Blood work may also be repeated 1-2 days after going home.  This is to make sure the kidney function levels have not increased.

So, how likely is survival?

Prognosis depends on many factors, including how significant the ingestion is, how soon the patient was decontaminated, whether or not the patient has already developed kidney failure, how soon treatment was initiated, and whether the clinical signs and kidney function levels have improved since treatment began. If a dog only ate a few grapes or raisins (depending on the size of the dog) and received immediate treatment, the prognosis is excellent. If the kidneys are damaged and no urine is produced, the prognosis is poor, and death is likely. The kidneys have very little ability to regenerate or repair themselves. Once they are damaged, they will not function as well as they did before the episode. When in doubt, seek treatment right away by contacting us. A veterinarian will estimate the prognosis for your dog based on symptoms, individual situation, and response to treatment.

Grape and raisin poisoning has only been identified as a problem in dogs. Since there are still many unknowns associated with this poisoning, it would be a good idea to avoid giving any grapes and raisins to your dog or any other pet.

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