Benign Prostatic Hypertrophy (BPH) in Dogs
Dr. Douglas Brum
Dogs and men are the only two species that experience BPH, but it is so common that nearly every intact dog is affected as they age. The prostate is located just behind the bladder and has two main parts or lobes. Above the prostate is the colon. Dogs with BPH usually have a symmetrical enlargement of both lobes. The enlargement is not painful. Some dogs, specifically the Scottish terrier, normally have larger prostates than other dogs. Most animals with BPH have no symptoms and feel fine. Many times the diagnosis is made on routine yearly physical examination. Prostatitis. Prostatitis is a bacterial infection of the prostate gland. Usually, the prostate is painful to palpation, and the dog often acts ill. A large prostate and a bloody discharge from the penis or blood in the urine are common signs. Prostatitis may be acute (sudden) or chronic (long term).
When an enlarged prostate (prostatomegaly) is found on physical, it is important to rule out the causes of pathologic (disease causing) prostatic enlargement. The diagnosis of BPH, itself, is a benign condition that often requires no treatment. As dogs age, testosterone and estrogen levels change, and the prostate cells become larger and more numerous and often form multiple small cysts throughout the prostatic tissue. With time, this leads to a prostate gland that gradually enlarges.
Unlike in people, the enlarged prostate gland usually does not cause problems urinating, but occasionally may cause changes in bowel movements. A prostate may grow large enough to put pressure on the colon and compress its diameter. Straining to defecate (produce a bowel movement) may be noted. Occasionally, stools formed may be flat and long, like a ribbon, because as the prostate enlarges, the diameter of the colon becomes flattened.
Along with the increase in prostatic size comes an increase in prostatic blood vessels, or vasculature, and the increase in blood supply may lead to the occasional clinical sign of bloody urine or a bloody discharge from the penis. Other diseases that cause an enlarged prostate gland or similar clinical signs include:
Prostatic abscess. An abscess is a walled off pocket of infection containing white blood cells, bacteria, and cellular debris. Abscesses occasionally form within the prostate gland in cases of chronic prostatic infections. They may get to be quite large and cause compression of both the colon and urethra. Straining to defecate or urinate may be seen, and most animals are feeling ill.
Paraprostatic cyst. Paraprostatic cysts are fluid-filled sacs that are connected to the prostate by a thin stalk. These can occur as a singular cyst or multiple cysts, and they can get very large.
Prostatic neoplasia (cancer). Prostatic cancer may closely mimic other types of prostatomegaly, but usually dogs with prostatic cancer have an asymmetric enlargement of one of the lobes of the prostate. Animals with prostatic neoplasia also tend to be systemically ill and have a history of weight loss. Tumors of the prostate are almost always malignant. The most common tumors involving the prostate are adenocarcinoma and transitional cell carcinoma. In contrast to most other types of prostatic disease, prostatic cancer occurs with the same frequency in both intact and neutered dogs. In a neutered male dog with significant prostatomegaly, prostatic neoplasia would be high on the list of potential causes.
Squamous metaplasia. Squamous metaplasia is a change in the prostate gland due to elevated blood estrogen levels. The prostate gland generally becomes bilaterally symmetrically enlarged. The main cause of this is an estrogen-producing tumor (Sertoli cell tumor). Long-term oral estrogen supplementation can also cause these changes.