Benign prostatic hyperplasia

What it is

Benign prostatic hyperplasia (BPH) is a spontaneous increase in the number (hyperplasia) and size (hypertrophy) of prostatic epithelial cells, driven by dihydrotestosterone produced from testosterone by 5α-reductase within the gland. It begins as glandular hyperplasia and progresses to a cystic form, with small intraparenchymal cysts. The enlargement is symmetrical and the gland stays non-painful. BPH also predisposes to prostatitis and prostatic cysts. It does not occur in dogs castrated before puberty.

Who it affects

Intact male dogs. Changes begin from early adulthood and are present in most intact males in middle and old age, but many have no signs.

Anatomy involved

• Prostate (prostata): in the dog it is the only accessory sex gland; it surrounds the proximal urethra at the neck of the bladder, at or just cranial to the pelvic brim. As it enlarges it can move cranially into the abdomen.
• Rectum: lies dorsal to the prostate; a symmetrical enlargement compresses it from below.
• Urethra: the prostatic urethra runs through the gland; unlike in men, urethral obstruction from BPH is uncommon in dogs.

Clinical signs

Often none. When present: tenesmus and thin, ribbon-like faeces from rectal compression; serosanguineous urethral discharge or blood dripping from the prepuce independent of urination; haematuria and haemospermia. Systemic signs (fever, pain) suggest prostatitis or abscess rather than uncomplicated BPH.

Diagnosis

• Rectal palpation: a symmetrically enlarged, smooth, non-painful prostate.
• Ultrasound: diffuse enlargement with uniform or slightly increased echogenicity and small cysts; it excludes abscess and neoplasia and allows guided sampling.
• Radiographs: prostatomegaly displacing the bladder cranially and the colon dorsally; mineralisation suggests neoplasia instead.
• Ejaculate cytology and culture or prostatic wash: to look for concurrent infection.
• Canine prostate-specific arginine esterase (CPSE): rises with prostatic enlargement and supports the diagnosis.

Treatment

Dogs without signs do not need treatment. Castration is curative: the prostate shrinks markedly within weeks. When the dog is to be kept for breeding, medical treatment with osaterone acetate (an antiandrogen), finasteride (a 5α-reductase inhibitor) or a deslorelin implant reduces prostate size and signs; the effect lasts only as long as treatment does. Prostatitis or cysts, if present, are treated at the same time.