Recursive uninstall?

Howdy. Is there a way that I can recursively uninstall a port and its dependencies? Somehow I have gnome-session installed with a zillion dependencies -- most of which have no other dependents. I don't know why it bugs me, but I want to uninstall all this mess that I don't use. a) Is there a hidden uninstall option that recursively removes dependencies if said port has no other dependents? b) Assuming not, can someone point me to the database describing the dependencies, so I could write a script to traverse the dependency tree? Recursively calling "port deps" is slow. If anyone else is interested in this script, I'll post it. Thanks