Foods allowed for kidney function test

I have been diagnosed with kidney function below 20%, told not to eat almost anything.  I was given list of foods NOT to eat, but was not given a food I can eat.    I need to know what I CAN eat for two weeks prior to test in two weeks?  I cannot eat meat of any kind, no vegetables of any kind (except potatoes).  Can I eat eggs?  What else can I eat?  I am 61 and I have a colonoscopy.