In a large saucepan, heat 2 tablespoons of olive oil. Add sausage. Once sausage is just starting to brown, add onion, celery and garlic. Cook together for about 8 minutes until the vegetables cook down and become translucent. Add stock, water and tomatoes. Bring to a boil. Stir in zucchini.
Reduce heat and simmer for 25 minutes, covered.
Add cooked tortellini and spinach. Serve topped with Parmesan.