Introduction: Static cold storage is the most commonly used preservation method for donated kidneys. One the of mostly used donor organ preservation method currently includes ice, ice box and 3 plastic bags. However, for kidney preserved for a long time, frostbites over donated kidney were noted at times. In our study, we proposed a novel kidney envelope that were used directly covering the donated kidney during kidney preservation.
Method: An animal model including 4 pairs of pig kidneys were used in our study. Each pair of pig kidney were separated into 2 groups. One kidney using the standard static cold storage method. Another we add a kidney envelope covering the kidney before immersing in Histidine-tryptophan-ketoglutarate (HTK) solution. Each pair of pig kidney was assigned into one of the fours groups: fully immersed in 100% HTK solution, partially immersed in 100% HTK solution, fully immersed in 50% HTK solution, partially immersed in 50% HTK solution. The area of frostbite of the pig kidney was observed, while the proportion of frostbite was confirmed by pathology. 
Results: Four pairs of pig kidney was experimented in our study. The enveloped-covered kidney showed a better resistance against frostbite based on our experiment. In the 2 fully immersed group, no grossly frostbite was noted. In the partially immersed groups, frostbite was noted in the 100% and 50% HTK solution group without kidney envelope, while no frostbite was noted in the enveloped group.
Conclusion: The novel kidney envelope may be beneficial in preventing frostbite in static cold storage for kidney preservation based on our pig kidney model.