Sorry to hear you are in the hospital. A low residue diet usually consists of no raw fruits, veggies, salads,seeds, nuts, coconut, popcorn, stringy meats, etc. The hospital will probably give you a list of foods that you shouldn't eat, just ask. You can also get a list if you google it.
It's really not that hard to follow and you just get used to it especially when you know what the alternative can be . I've followed the diet since my subtotal last July due to diarrhea issues and the only thing that I really miss is salad and watermelon but after reading about all of the obstructions on here, I'll just stay on the diet.
I hope you feel better soon,