Enlarged prostate in the intact dog: ultrasound interpretation

Question

Intact 8-year-old male Collie with intermittent bloody urethral discharge unrelated to urination and mild tenesmus. He is afebrile and rectal palpation is not painful. Transabdominal ultrasound of the prostate, with measurements marked:

Transabdominal ultrasound of a dog's enlarged prostate, with small anechoic areas and measurement callipers — Image: Kalumet · CC BY-SA 4.0, Wikimedia Commons

What is the most likely interpretation?

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A. Prostatic carcinoma, because intraparenchymal cysts indicate malignancy

Small cysts are common in hyperplasia. Mineralisation, marked asymmetry, loss of the capsule, enlarged medial iliac lymph nodes or a large prostate in a neutered dog suggest neoplasia.

B. Benign prostatic hyperplasia, the commonest cause of an enlarged prostate in intact dogs

Correct. Almost all older intact dogs develop it under the influence of dihydrotestosterone. The prostate enlarges symmetrically, with homogeneous or slightly heterogeneous parenchyma and small cysts, and it often causes bloody discharge and tenesmus.

C. Paraprostatic cyst, a cavity separate from the prostatic parenchyma

A paraprostatic cyst is a large cavity outside the parenchyma, attached to the prostate by a stalk. Here the cysts are small and lie within the gland.

D. Prostatic abscess, requiring urgent surgical drainage

An abscess usually comes with fever, pain on palpation and cavities with echogenic contents. This dog is afebrile and not painful. If in doubt, cytology and culture of prostatic fluid.

lightbulb Key takeaway

In an intact dog, think of hyperplasia first (often with cysts and sometimes concurrent prostatitis). In a neutered dog, a large or mineralised prostate is neoplasia until proven otherwise. Ultrasound guides; cytology, culture of ejaculate or prostatic wash, and biopsy confirm.

What is the most likely interpretation?

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