In 1-quart saucepan, heat 1 cup water to boiling over high heat. Add rice, heat to boiling. Reduce heat to low, cover and simmer 15 to 20 minutes until water is absorbed and rice is tender.
Meanwhile, in 4-quart saucepan, heat chicken broth and 2 cups water to boiling over high heat. Add carrots and celery, heat to boiling. Reduce heat to low, cover and simmer 5 to 7 minutes, until vegetables are tender. Stir in spinach, rice, and sliced meatballs, heat through.
Serve soup with Parmesan cheese if you like.
Without Parmesan cheese per serving: About 300 calories, 25 g protein, 30 g carbohydrate, 7 g total fat (3 g saturated), 51 mg cholesterol, 1010 mg sodium.