Many owners are unaware of the potential toxicity of grapes, raisins and grape seed extracts to their dogs.  This seemingly harmless fruit can kill a dog with just a very small amount ingested.  Certain elements of the grape become toxic to the canine kidney and cause the pets to go into acute kidney failure.  Why this affects dogs versus people is based on species-specific differences in how the grape metabolites are handled.  

We don’t have a lot of specific information on what quantity of grapes or raisins it takes to kill a dog, but in general  0.05 ounce of raisins per pound of body weight is enough to be toxic and potentially lethal.  That means that an average 2 oz box of raisins can kill a 40 pound dog.  A small 10 pound dog could be killed by as little as a ¼ of a box.    For grapes, 0.35 oz per pound would be toxic  or about 3.5 oz per 10 pounds of body weight would be toxic. 

How do we treat grape/raisin toxicity?

The first line of defense in treating this problem is to get the offending fruit out of the body if the ingestion has occurred within 4-6 hours of presentation.  We can induce vomiting using various drugs.  Next we introduce activated charcoal by mouth to help absorb the toxins and reduce the amount that is taken into the body.    We take blood tests at the time of admission to find out what the resting levels of the kidney function and rest of the organ systems are at.   Once this is complete, we must administer intraveneous fluids to help improve blood flow through the kidneys so that the toxin has less time to affect the kidney cells.  After 2 days, we recheck the kidney function. If it is normal, there is a good chance that the pet will do all right.  If the kidney enzymes are climbing, the prognosis becomes guarded.  Continued fluid therapy and supportive care will be effective in some cases and not in others. 

What is the prognosis for pets that survive treatment?

If the dog responds to therapy and survives the treatment, the prognosis depends on whether or not the kidneys have sustained significant damage from the toxin.  If the kidney blood values are normal at the time of discharge, the pet will probably do fine.  Unfortunately, the blood tests we track to follow kidney function are not that precise.  In fact, they do not tend to rise until at least half of the kidney function has been impaired.  This means that even with “normal” blood values, there may have been significant damage to the kidneys.  This may lead to premature kidney failure later in life. 

Because of this potential sub-clinical damage, we normally check the kidney function 5-7 days after going home and then at 1 month and 6 months after the toxic insult.