In a large soup pot, heat oil over high heat. Add sausage, onion, and garlic, and cook 6 to 8 minutes, or until no pink remains, stirring frequently to break up the meat.
Add remaining ingredients except spinach; bring to a boil. Reduce heat to low and simmer,
uncovered, for 30 minutes, or until thickened. Stir in spinach, and serve.