Toxicity from the combination of multiple food contaminants

Melanine + cyuranic acid -> crystalline nephrophathy. Emphases mine.

Pet food contamination mystery unlocked | KOMO-TV - Seattle, Washington | News

...Scientists from Canada and the U.S. believe they may have unlocked the mystery. They've learned that melamine combined with another contaminant found in the pet food--- cyuranic acid-- forms crystals in the kidneys.

"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," Wilderman said.

The crystals are suspected of killing the pets, and the ASPCA has just seen a case that suggests that's exactly what happened.

"We had one case recently where the cats' 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," said Dr. Louise Murray, with the ASPCA Animal Hospital...

One wonders how many different contaminants have been introduced into the Chinese supplied pet food ingredients. The list keeps growing. I missed this story yesterday, but Google already has over 200 hits on the topic.