Preheat oven to 350 degrees.
Brown sausage in heavy skillet over medium heat; transfer sausage to a 2 ½-quart greased casserole dish. In the sausage drippings, sauté celery, onion, peppers and mushrooms until lightly browned; transfer to casserole.
To the casserole, add the water chestnuts, rice, broth and seasonings; mix well. Cover tightly and bake for 1 to 1½ hours or until rice is fluffy and tender.