Unilateral scrotal enlargement in a 16-month-old black Angus bull

HealthCenter Livestock Services in July 2023 to evaluate unilateral scrotal swelling.The bull was first noticed being ridden by other yearling bulls in the pasture 1 day before presentation, which prompted the owner to notice the scrotal swelling.The bull is housed on a 160-acre pasture with 75 yearling bulls and is the only animal affected.No history of prior medical conditions was reported, and he is vaccinated against clostridial diseases.On physical examination, the bull was bright, alert, and responsive and had a slightly increased heart rate (88 beats/min; reference, 50 to 80 beats/min), normal respiratory rate (48 breaths/ min; reference range, 26 to 50 breaths/min), normal temperature (39 °C; reference range, 36.7 °C to 39.1 °C) with pink and moist mucous membranes.Upon visual examination, the scrotum was asymmetrical.Visually, the left scrotal sac appeared enlarged, with diffuse swelling extending proximally to the neck of the scrotum (Figure 1).Upon palpation of the scrotum, the left side was firm and edematous, making distinguishing the testicle and the epididymis difficult.The right testicle was easily movable within the scrotum and the epididymis palpated normally with no adhesions or firm nodules.Subjectively the testicle was soft on palpation, which deviates from the normal turgid texture.Transrectal palpation and scrotal ultrasonography ruled out an inguinal hernia.Formulate differential diagnoses, then continue reading.