According to the CNN website scientists and veterinarians have discovered that a mixture of two compounds have caused the kidney failure that has led to almost 4000 pets.  The melamine found in the tainted foods are not at levels that would normally kill and animal but mixed with another compound, cyanuric acid, can produce crystals that may have been a deadly combination. 

"What we've done is experiments that show if you take cat urine and you add melamine to it and cyanuric acid, the crystals will form in the cat urine in a test tube as we're watching them, so it happens within a matter of hours," said Alan Wildeman, vice president of Canada's University of Guelph, which is renowned for its veterinary research center.

Crystals blocked the tubes leading from the kidneys to the bladder in one cat operated on recently at the Bergh Memorial Animal Hospital inside the ASPCA's New York headquarters, according to Dr. Louise Murray, the group's director of medicine.

"The cat's kidneys were completely obstructed, and when we went to surgery to relieve the obstruction, there was no normal stone. Instead, the ureters were completely full of these melamine-type crystals," she said.

The FDA said Friday it had received more than 17,000 consumer complaints about the tainted pet food, including the deaths of 1,950 cats and 2,200 dogs.

The FDA has officially tallied 16 animal deaths related to the pet food recall, which spread to include more than 60 million packages of nearly 100 brands of pet food.

Another poison that can cause kidney failure because of crystals in the ingestion of antifreeze by pets.  I will post more on that tomorrow.