Figuring out what sparse fields are present in ES index

Hi All,
I am using doc_values for all of my fields in ES 1.7.3, and lately have been noticing disk usage growth. I do have some sparse fields that are contributing to this growth, but I do not know which they are. Is there any tool that can help me figure out what sparse fields are present in my index? Can I run an elasticsearch query etc to figure that out?

Please advice.

Thanks,
Madhav.