Heat a large Dutch oven over medium-high heat; add the Italian sausage and cook while breaking it into small crumbles until browned and fully cooked.
Remove the sausage from the pot and set aside, retaining approximately 1 tablespoon of rendered fat in the pot; add olive oil if additional fat is needed.
Add the onion, carrots, and celery to the pot and sauté for 5-7 minutes until the vegetables begin to soften.
Stir in the minced garlic, dried oregano, and red pepper flakes, cooking for 60 seconds until fragrant.
Return the cooked sausage to the pot and add the cannellini beans and chicken bone broth.
Bring the mixture to a boil, then reduce heat to low and simmer uncovered for 15 minutes to integrate flavors.
Stir in the chopped kale and cook for 3-5 minutes until the leaves are wilted and tender.
Remove from heat, stir in fresh lemon juice, and season with salt and pepper to taste.
Ladle into bowls and garnish with grated parmesan cheese before serving.