it would be considered proctosigmoiditis or proctitis if it's not up into the sigmoid...depending on your own rectal/colon measurements.. Left-sided is definitely past the sigmoid and up to the splenic flexure...some may have it somewhere between.
Nonspecific means not determined as of yet. Sounds like UC, and hopefully the doc took biopsies, which will help in the diagnosis by making sure there are no other culprits for the severe inflammation. There are a few things that can mimic UC.
CD can also happen in the pattern of UC and in the early stages will look exactly like it until it affects deeper than the mucosal/submucosal layer.
quincy