Rats- Puffy cheeks

Question
QUESTION: I have a two and a half year old rat, Noel, with puffy cheeks that sort of resemble a chipmunk. She has one benign mammary tumor but other than that she's has healthy as can be. She is still very active and doesn't act like she's in pain, she's also still eating and drinking. When I noticed it today I got out my younger rat who is over a year old and her cheeks were normal. I currently have three rats but Noel lives alone in one level cage due to bullying by the younger rats and clumsiness in her old age.
I've looked all over the Internet and all I can find is information about abscesses and such. I don't think it's an abscess because both her cheeks are puffy and she's not acting painful. I also haven't changed her diet so I don't think it's an allergic reaction.
I have had five rats in total and never seen anything like this. Please help

ANSWER: Hi Faith,
Since it is symmetrical, it seems unlikely it is abnormal. Sometimes my rats' cheeks look bigger than normal, but then I realize it's just the way I'm looking at them. Have you felt them to see if the actually feel bigger? Could it just be the fur that's fluffed out?
Deb

---------- FOLLOW-UP ----------

QUESTION: No, her fur is actually really thin. My mother also said they seemed swollen and she's the one that usually tells me I'm overreacting when it comes to my rats. I felt them and they're just squishy like normal skin. Should I just wait it out and see if it goes away?

Answer
I'm thinking some things that might possibly cause it would be an allergy, or maybe kidney failure. Have you fed her anything unusual lately? If it's an allergy it should go away fairly quickly.

For kidney failure, you want to reduce the amount of protein and salt they get and encourage them to drink a lot of liquids. You can also do this by feeding a lot of fresh fruits and veggies, and soaking rat blocks in water.