I'm so sorry you're in the hospital with a blockage.
With a low residue diet, think soft and easily digestible. For breakfast, you can have a variety of cereals, like Cheerios, or toast with seedless jam, and for lunch, soup and sandwich is a good choice. For dinner, you can eat non-fibrous cooked veggies with lean meats, like chicken breast. Protein shakes with banana are good any time of day.
I hope the blockage clears soon, so you can go home and start eating soft foods. ((hug))
Be careful with the mushrooms - I do better with canned mushrooms than the fresh ones, and even worse with the dyhydrated then rehydrated ones. Sometimes, I think pizza shops use these and they can be pure hell on my gut. Esp. if I have leftover pizza and reheat it. They do not digest well for me. Now, canned ones that don't get dried out, like if they stay in a marinara sauce, I'm ok with. Love small zuchini chunks (very young zucchini with the skin on but no seeds) in my pasta sauce too. I used to throw in a lot of veggies, but DH has come up with some veggie allergies so I am now limited on his behalf too.
One of the easiest summer pasta dishes uses ranch dressing in place of Italian dressing in making a pasta salad. I use the Mini Bow Tie pasta lately. Tho I did just buy a box of Mini Wheels (piccolini). And shredded cheese. I am a dairy-aholic .. Sorry. And pieces of crispy bacon (but I have used chicken), and about anything else you'd like to throw in it that sounds good. I shredded some raw carrot and thin sliced just a few radishes for color, added some parsley, ground pepper, ground sea salt. A Meal or a sidedish.
How about an olive oil/garlic & dried roasted red pepper or sun dried tomato infused sauce of sorts on linguine or spaghetti. I usually always have a small jar of Olive Oil in the fridge with sundried tomatoes in it... add some salt, basil, garlic and grated parmesan or whatever other topping you might like. Crushed red pepper flakes is what my DH likes.
You got the idea... Marinara pasta is a good idea for you. Can you eat any cheeses? Can you use soy milk to make a cheese sauce? You could use that on Farfelle or Elbows or rotini. Chicken, Tuna, Turkey ... all good meats.
I usually throw stuff together.. I do have some recipes I can look up if you are interested. Let me know. I cook more by method than directly from recipes. Like Rachel Ray says.. once you have the method, you can switch ingredients and make your own! (lol) My husband, when he really likes something, tells me to write the ingredients down. By that point, I don't even remember what all I have added (not really)!!!!