Ultrasonography of the parathyroid glands as an aid in differentiation of acute and chronic renal failure in dogs - Reusch, CE; Tomsa, K; Zimmer, C; Hoerauf, A; Nett, C; Unterer, S; Glaus, TM; Schlittner, E; Pospischil, A (J Am Vet Med Assoc, 2000)