In a large non-stick skillet, brown sausage slices and set aside. Combine cornstarch, pineapple juice, brown sugar, vinegar and soy sauce. Pour into skillet and cook, stirring constantly until sauce thickens and boils. Continue cooking 1 more minute, then add the sausage back to the pan along with the pineapple and water chestnuts. Let simmer, stirring frequently until heated through. Serve over the cooked rice.