Greenies dog treat lawsuit settled

[snopes]

The makers of Greenies, one of the nation's best-selling dog treats, have settled a class-action lawsuit claiming the teeth-cleaning product injured or killed close to a dozen dogs.

http://www.businessweek.com/ap/finan.../D8RNH0V00.htm

[franjava]

My friend's Shih Tzu (sp?) swallowed one whole (to keep another dog from getting it) and ended up in kidney failure. Friend had to inject saline under the dog's skin so many times a day (2?-3?) to keep her hydrated. When the dog finally died about two years later, she was skin and bones (having been overweight before hand) and trembled all the time. I can't believe the dog lived as long as she did.

ETA: Friend was not in on the lawsuit.

[Xia]

I'm a little confused. How did swallowing the treat whole cause kidney failure?