Benign prostatic hyperplasia (BPH) is a spontaneous, age-related, noncancerous enlargement of the prostate gland in sexually intact male dogs. BPH is the most common prostatic disorder in sexually intact male dogs. BPH has not been reported in cats.
Although BPH in dogs has historically been used as an animal model of BPH in humans, considerable anatomical and pathophysiological differences exist between species.
Etiology and Pathophysiology of Benign Prostatic Hyperplasia
Benign prostatic hyperplasia results from androgenic stimulation or an altered androgen:estrogen ratio.
Within prostatic epithelial cells, the enzyme 5-alpha reductase converts testosterone secreted by the testes to the biologically active hormone dihydrotestosterone (DHT). DHT promotes symmetrical, progressive, eccentric prostatic parenchymal enlargement (ie, BPH). Estradiol and other growth factors also are also involved.
BPH involves an increase in both prostatic cell numbers (hyperplasia) and cell size (hypertrophy). Intraparenchymal prostatic cysts can form.
It is not known why some males are affected and others are not.
Glandular hyperplasia can begin in some dogs as young as 2.5 years old, and after age 4, cystic hyperplasia tends to develop.
Pathological changes associated with BPH may increase susceptibility to prostatitis.
Clinical Findings of Benign Prostatic Hyperplasia
Benign prostatic hyperplasia in dogs is not always problematic, and many sexually intact male dogs with BPH (with or without concurrent chronic prostatitis) are clinically normal or develop clinical signs of hemospermia and/or infertility only. When present, other clinical signs include persistent or intermittent hematuria and hemorrhagic preputial discharge.Clinical signs may become evident or worsen when males are exposed to estrous females.
Diagnosis of Benign Prostatic Hyperplasia
Diagnosis of BPH is suggested by history and physical examination findings. On rectal examination, palpation of the prostate typically reveals a nonpainful, symmetrically enlarged prostate.
Radiography can confirm prostatomegaly (see prostatomegaly radiograph). The prostate is not normally visualized on radiographs.
Courtesy of Dr. Ronald Green.
Ultrasonographic imaging should show diffuse, relatively symmetrical prostatic enlargement. Ratios of prostatic dimensions (length, width, and height) to aortic luminal diameter have been found to be useful for evaluation of the size of the prostate in dogs, independent of body condition (1).
In cases of cystic BPH, ultrasonography may reveal hypoechoic to anechoic, miliary to large, thin-walled intraprostatic cystic structures (see image of cystic BPH). In contrast, paraprostatic cysts are extraparenchymal and are larger than the inclusion cysts seen with BPH.
Courtesy of Dr. Michelle Kutzler.
Cytological examination of massage or ejaculate specimens reveals hemorrhage with mild inflammation without evidence of sepsis or neoplasia.
Definitive diagnosis of BPH requires histological evaluation of a prostatic biopsy or cytological evaluation of a fine-needle aspirate of the prostatic parenchyma or of an intraprostatic cyst.
Differential diagnoses for prostatomegaly include prostatitis and prostatic neoplasia.
Treatment of Benign Prostatic Hyperplasia
In cases of benign prostatic hyperplasia, castration is the treatment of choice for dogs not intended for breeding or showing. With castration, prostatic involution is usually evident within a few weeks and is often complete in several months.
For males intended for breeding or showing, medical antiandrogen therapy is an option.
Treatment with the 5-alpha reductase inhibitor finasteride (0.1–0.5 mg/kg [or 5 mg/dog for dogs weighing 10–50 kg], PO, every 24 hours for 16 weeks) reduces hypertrophied prostate volume, resolving clinical signs while maintaining normal testosterone concentrations, with no deleterious effect on semen quality, fertility, or libido. Treatment for 16 weeks produces a significant reduction in prostate size, but dogs must remain on the medication for the rest of their lives or prostatic hypertrophy will return.
Osaterone acetate is a testosterone analogue available in Europe with potent antiandrogenic activity. Treatment with osaterone (0.25–0.5 mg/kg, PO, every 24 hours for 7 days) has been found to resolve clinical signs of BPH in approximately 50% of dogs within 14 days; effects last for at least 5 months. Semen quality and fertility are not adversely affected and in some cases may improve.
A subcutaneous implant containing the GnRH agonist deslorelin, which is labeled to suppress testosterone concentrations to induce temporary infertility in healthy, sexually intact male dogs, is available in Canada, Mexico, Australia, New Zealand, South Africa, and Europe, as well as most of South America and Asia. With no testosterone available, dihydrotestosterone cannot be produced, and the prostate gland volume decreases by up to 60%. Deslorelin must be administered every 6–12 months, depending on the formulation used (4.7-mg implant versus 9.4-mg implant). Unlike in finasteride and osaterone treatment, spermatogenesis and fertility are arrested during the implant's period of activity.
In a study of 2 dogs with BPH, phytotherapeutic treatment with the herb Epilobium parviflorum (300 mg/dog [9–25 mg/kg], PO, every 24 hours for 60 days) decreased prostate volume by 40% and decreased serum testosterone concentration by 20–30% without apparent adverse reactions or complications (2).
In another study, treatment with the crude polysaccharide fraction of the roots and stems of the herb Urtica fissa (120 mg/kg, PO, every 24 hours for 3 months) resulted in a 21% decrease in prostate volume in dogs with BPH (3). Further research is needed before this can be recommended as a treatment.
In a study using dogs with BPH to model human BPH, ultrasonic prostatic ablation under MRI guidance demonstrated some success (4). An MRI-compatible transurethral device incorporating a tubular transducer array with dual 120° sectors was used to ablate canine prostate tissue. Ablated prostate regions demonstrated complete apparent resorption of ablated tissue, with formation of cystic regions containing fluid within 31 days. The treatment's effect on fertility was not assessed.
In another study using dogs with BPH to model human BPH, pulsed electromagnetic field therapy was administered to the prostate in 20 dogs with BPH at a rate of 5 minutes every 12 hours for 3 weeks (5). Pulsed electromagnetic field therapy resulted in a substantial decrease in prostatic volume without altering semen quality, testosterone concentrations, or libido.
Key Points
Benign prostatic hyperplasia (BPH) is the most common prostatic disorder in sexually intact male dogs.
Clinical signs include persistent or intermittent hematuria, hemospermia, and hemorrhagic preputial discharge are most commonly reported; dogs are often subclinically affected.
Transabdominal ultrasonography is the best method for evaluating the prostate size and echotexture.
Castration is the treatment of choice in dogs not intended for breeding or showing; for males intended for breeding or showing, medical therapies are effective as long as treatment is continued.
For More Information
Cunto M, Ballotta G, Zambelli D. Benign prostatic hyperplasia in the dog. Anim Reprod Sci. 2022;247:107096.
Posastiuc FP, Constantin NT, Domain G, Van Soom A, Diaconescu AI, Codreanu MD. A systematic review of medical treatments for benign prostatic hyperplasia in dogs: evaluating strategies for reproductive function preservation. Vet Sci. 2025;12(1):70.
Also see pet owner content regarding prostatic diseases in dogs and prostatic diseases in cats.
References
Ponglowhapan S, Pattanaviboon K, Maneerattanavichien Y, et al. Ultrasonographic measurement of the prostatic dimension-to-aortic luminal diameter in healthy intact male dogs and dogs with benign prostatic hyperplasia. J Small Anim Pract. 2024;65(11):789-798. doi:10.1111/jsap.13766
Cazzuli G, Damián JP, Minini L, Ferreira F, Suárez G, Pessina P. Use of Epilobium parviflorum in the treatment of benign prostatic hyperplasia in canines. Vet Med Sci. 2025;11(2):e70205. doi:10.1002/vms3.70205
Xiaocheng C, Shan H, Yuxing L, et al. Inhibition of spontaneous canine benign prostatic hyperplasia by an Urtica fissa polysaccharide fraction. Planta Med. 2015;81(1):10-14. doi:10.1055/s-0034-1383364
Sommer G, Pauly KB, Holbrook A, et al. Applicators for magnetic resonance-guided ultrasonic ablation of benign prostatic hyperplasia. Invest Radiol. 2013;48(6):387-394. doi:10.1097/RLI.0b013e31827fe91e
Leoci R, Aiudi G, Silvestre F, Lissner E, Lacalandra GM. Effect of pulsed electromagnetic field therapy on prostate volume and vascularity in the treatment of benign prostatic hyperplasia: a pilot study in a canine model. Prostate. 2014;74(11):1132-1141. doi:10.1002/pros.22829
