Fluid retention can come from gabapentin and Lyrica.

It also comes from eating too many sweets and carbs.

And there is also a condition, called hereditary angioedema (which I have) which will cause swelling. It can be acquired by using ACE inhibitor drugs for blood pressure. It is very sneaky and a fairly new diagnosis, and many doctors don't know about it.

http://www.haea.org/

Right now I have a swollen left hand...for no reason! (other than some trauma and minor surgery to my toe!).

There are special blood tests for this, described on that site.