Hello,

I am still working on this.   My first reaction is that it is kudzu. But that is not correct. Kudzu has 3 lobed leaves- or three distinct leaflets on a petiole. - Now if you see this on the older leaves, the size alone would be consistent with kudzu.

My second impression is that of Moonflower- or ipomeaea alba which is said to be 10-30' but has a distinct white flower- but may not be blooming if it is heavy shade, and the leaves are more deeply cleft at the petiole.

So. what is left.....

I have gotten it down to a species of Dutchman's pipe- Aristolochia sp. It would be unusual for it to grow that large, but it is a possibility.

Is it possible for you to take a sample to your local Extension office or Extension Master Gardener program? 

Good luck.