Grapes and Their Dried Products (Raisins, Sultanas, and Currants)
Grapes, the fruits of Vitis vinifera, and their dried products (raisins, sultanas, and currants) have been reported to cause renal failure in dogs. The fruits may be ingested raw or cooked as ingredients of fruit cake, mince pies, malt loaf, snack bars, scones, and other baked goods (28). The toxic syndrome has also been observed with consumption of marc (the residue of grapes after pressing).
The toxic principle(s) and the exact mechanism of grape-induced nephrotoxicity are still unknown. The latter appears to involve a nephrotoxic agent or an idiosyncratic reaction, leading to hypovolemic shock and renal ischemia. There is considerable variation in the susceptibility of dogs to grapes and their dried products. In a recent study that reviewed 180 reports recorded by the VPIS between August 1994 and September 2007 on the ingestion of Vitisfruits by dogs, some animals were reported to remain asymptomatic after ingesting up to 1 kg of raisins while others died following the ingestion of just a handful. Published case reports have identified renal failure in dogs following the ingestion of estimated doses of raisins as low as 2.8 mg/kg and as little as four to five grapes in a dog weighing 8.2 kg. Therefore, ingestion of any quantity of these fruits should be considered as a potential clinical problem. Vomiting within 24 h of ingestion is the typical clinical sign observed. Diarrhea, anorexia, lethargy, and abdominal pain have also been reported. Partially digested grapes and grape products may be present in the vomit, fecal material, or both. This is followed by signs of renal insufficiency or failure (oliguria, anuria, polydipsia, proteinuria, and elevated serum concentrations of creatinine and urea) within a short period. In cases of dogs with oliguria or anuria, the prognosis is generally poor. The time taken to administer treatment may also play a significant role in the outcome.
Given the large variability in the tolerance exhibited by dogs, the ingestion of any quantity of grapes or grape products by dogs should be handled aggressively. Following recent ingestion, prompt decontamination using emetics and repeated doses of activated charcoal is highly recommended. All dogs should receive aggressive intravenous fluid therapy for a minimum of 48–72 h, and their renal function should be monitored for at least 72 h.