In a large non-stick skillet over medium heat.
Add onion, celery, and carrots to the skillet and cook until crisp-tender, (about 3-4 minutes) stirring occasionally.
Move the vegetables/dressing mixture to the slow cooker.
Add diced tomatoes, beans, chicken broth, water, and Italian seasoning, stirring the ingredients together before covering with the lid.
Cook on HIGH for 3 hours, or LOW for 6 hours.
Stir in the pasta and baby spinach, cooking for an additional 10-15 minutes, until pasta is tender.
Season with salt & pepper to taste. Garnish bowls with parmesan cheese just before serving.