Hen with a puffed up rear end

[viperj82]

Hi everyone
This afternoon we noticed that one of our hens has got a puffed up rear end and she is not moving much and we have not seen her eating. Is there anything we should be looking at or looking for. We are pretty new to having chickens so any help would be appreciated.

 

[karstenwhyte]

Could you possibly post a pic of her vent area so I can check to see if infection is a possibility.