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The consumption of grapes and raisins presents a potential health
threat to dogs. Their toxicity to dogs can cause the animal to
develop acute renal failure (the sudden development of kidney
failure) with anuria (a lack of urine production). The phenomenon
was first identified by the Animal Poison Control Center (APCC),
run by the American Society for the Prevention of Cruelty to
Animals (ASPCA). A trend was seen as far back as 1999.[1]
Approximately 140 cases were seen by the APCC in the one year from
April 2003 to April 2004, with 50 developing symptoms and seven
dying.[2]


Cause and pathology

The reason some dogs develop renal failure following ingestion of
grapes and raisins is not known. Types of grapes involved include
both seedless and seeded, store bought and homegrown, and grape
pressings from wineries.[3] A mycotoxin is suspected to be
involved, but one has not been found in grapes or raisins ingested
by affected dogs.[4] The estimated toxic dose of grapes is 32 g/kg
(1.1oz/kg) (grams of grapes per kilograms of mass of the dog), and
for raisins it is 11-30 g/kg. (0.39 - 1.06 oz/kg) [5] Dogs suffer
acute renal failure after ingesting 3 grams per kilogram of raisins
or dry matter of grapes. (Dry matter is calculated as 20% of grape
weight).[6] The most common pathological finding is proximal renal
tubular necrosis.[7] In some cases, an accumulation of an
unidentified golden-brown pigment was found within renal epithelial
cells.[6]

Symptoms and diagnosis

Vomiting and diarrhea are often the first symptoms of grape or
raisin toxicity. They often develop within a few hours of
ingestion. Pieces of grapes or raisins may be present in the
vomitus or stool. Further symptoms include weakness, not eating,
increased drinking, and abdominal pain. Acute renal failure
develops within 48 hours of ingestion.[4] A blood test may reveal
increases in blood urea nitrogen (BUN), creatinine, phosphorus, and
calcium.

Treatment

Emesis (induction of vomiting) is the generally recommended
treatment if a dog has eaten grapes or raisins within the past two
hours. A veterinarian may use an emetic such as hydrogen peroxide
or apomorphine to cause the dog to vomit. Further treatment may
involve the use of activated charcoal to adsorb remaining toxins in
the gastrointestinal tract and intravenous fluid therapy in the
first 48 hours following ingestion to induce diuresis and help to
prevent acute renal failure.[1] Vomiting is treated with
antiemetics and the stomach is protected from uremic gastritis
(damage to the stomach from increased BUN) with H2 receptor
antagonists. BUN, creatinine, calcium, phosphorus, sodium, and
potassium levels are closely monitored. Dialysis of the blood
(hemodialysis) and peritoneal dialysis can be used to support the
kidneys if anuria develops. Oliguria (decreased urine production)
can be treated with dopamine or furosemide to stimulate urine
production.[5]

The prognosis is guarded in any dog developing symptoms of
toxicosis. A negative prognosis has been associated with oliguria
or anuria, weakness, difficulty walking, and severe hypercalcemia
(increased blood calcium levels).[7]

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