My vet also feel that it can bear some relation to a camel's hump (don't throw me out for that comment!!). He feels that it can be a fat store that some cats (especially those who come from long lines of feral stock) use to help them carry them through the lean seasons. He ahs also told me that some cat owners are now paying to have these pouches removed for cosmetic reasons - something of which he basically disapproves.
Well at first I would rather it not be there, but now that I understand it, Iím fine with it.
I saw a mountain lion in the wild a few weeks ago and noticed the same pouch. At the time I figured it had just eaten a deer or something.