Ok, we got the idiom "be scared to death" = "feel extremely frightened" (see http://idioms.thefreedictionary.com/scare+to+death)
"be scared to death" does not mean "you are scared that you will be die".
Likewise, I want to express the idea that you are so scared that you almost pee in your pan?
So, can I use the expression "be scared to pee". However, when searching that term in Google, it shows many results like "The 3 years old boy is scared to pee" which means "he is afraid of peeing" but does not mean "he is extremely afraid of something to a level that he almost pees in his pan"
How to express the idea that you are so scared that you almost pee in your pan?