If you care and want to read up on it at all, here's a few articles I'd saved when I had lost some out of my litters to issues with megacolon. Pretty dull reading if you ask me but good to know if you raise your own feeders...just something to be aware of more than anything and not something to stress over.
http://ratguide.com/health/digestive/megacolon.php
http://www.spoiledratten.com/highwhitecont.html
http://www.ratfanclub.org/megacolon.html