Heat olive oil in a large pot over medium heat.
Add onion and garlic, sauté until onions are translucent.
Toss in the carrots, celery, zucchini, and leek.
Cook for about 5 minutes, stirring occasionally.
Stir in oregano and add shredded chicken, tomatoes, and chicken broth.
Bring to a boil.
Add pasta to the pot and reduce heat.
Simmer for 10-12 minutes or until pasta is cooked.
Mix in the spinach and season with salt and pepper.
Cook for an additional 2 minutes to wilt the spinach.