Site-URL will change: how to keep statistics

Hi, I´m running Piwik in a cms installation, so multiple sites (200+) are tracked.

Until now the urls of the pages contain parameters, so these no path-like url.

example: www.host.com/portal/page.php?navigationid=2&articleid=5

But that will change in the near future.

example: www.host.com/politics/foreign_policy/articlename-5.html

The problem ist (I think its a problem) that until now the url is used as the identifier for tracking. But if that identifier will change, the same pages will be tracked under a new url.

Is there any possibility how to prevent that?

Thanks in advance