A 12-year-old spayed female domestic shorthaired cat is brought to the hospital by his owner. The patient has had episodes of vomiting and anorexia for 3 to 4 days. The patient has not been able to eat solid food and is not drinking. The referring veterinarian identified bilaterally enlarged kidneys on abdominal palpation. The cat was started on oral mirtazapine (appetite stimulant) and tramadol (pain medication), but the owner has seen no improvement in the first 24 hr.