Combine the onion, minced garlic and green pepper in a large stockpot. Add in about 1/2 of 1 can of broth and cook for about 7-8 minutes on medium heat. Add the remaining broth, tomatoes, mushrooms and sausage. Heat just until boiling, and then add the salt, Italian seasoning and uncooked pasta. Cover and simmer 20 minutes. Add in water until your desired consistency is achieved. Heat an additional 5 minutes.