Remove casings from sausage; cut sausage into 1/2-in. slices. In a 6-qt. stockpot, heat oil over medium-high heat. Add sausage, carrots, celery, onion and garlic in batches; cook and stir until vegetables are crisp-tender.
Add broth, water, lentils and bay leaf; bring to a boil. Reduce heat; simmer, covered, 20-25 minutes or until lentils are almost tender.
Stir in remaining ingredients. Bring to a boil. Reduce heat; simmer, covered, 15 minutes or until lentils are tender. Remove bay leaf.