NAVLE Practice Test 5

A 3-year-old castrated male indoor domestic shorthair cat is presented for straining, frequent small urinations and blood-tinged urine for 2 days, beginning shortly after a new cat joined the household. He eats only dry food. Temperature 101.6°F (38.7°C), heart rate 180 beats/min, respiratory rate 30 breaths/min. The bladder is small and slightly painful, and the urethra is not obstructed. Urinalysis of a cystocentesis sample shows urine specific gravity 1.055, pH 6.5, many red blood cells, no crystals and no bacteria; urine culture is negative. Abdominal radiographs show no calculi. Which of the following is the most likely diagnosis?