Lethargic cat with pale mucus membranes

History of Present Illness

A 6-year-old, castrated male, domestic medium-hair cat is brought to the clinic by his owner for further evaluation. The cat had been missing for a week, and when he returned home he had a forelimb wound, presumably due to a bite. The wound was treated, and the patient was given nonsteroidal anti-inflammatory (NSAID) and antimicrobial medications. Two days later, the owner reports the patient ate only half his food, and the following morning he did not get up to eat at all. At that time, the patient's mucus membranes were pale in the morning and are almost white now in the clinic.