Enlargement of a male dog’s prostate gland is not especially difficult for a veterinarian to diagnose. Careful rectal and abdominal palpation by a skilled veterinarian is the best way to identify an enlarged prostate. Rectal palpation will reveal a symmetrically enlarged prostate gland – called “prostatomegaly” - in intact male dogs that have developed benign prostatic hyperplasia (BPH). However, physically manipulating the prostate gland cannot help the veterinarian determine the cause of the enlargement; in other words, palpation cannot help the veterinarian distinguish between benign prostatic hyperplasia, cystic prostatic disease, prostatic neoplasia (cancer) or bacterial infection and inflammation of the prostate gland (bacterial prostatitis; prostatic abscessation). If the prostate is abnormally large in a neutered male dog, cancer should be on the top of the differential list.
The results of routine blood work (a complete blood count and serum biochemistry profile) on dogs with BPH will typically be normal, unless they have some other unrelated medical disease or disorder. A urinalysis usually will also be unremarkable, but occasionally dogs with BPH may have blood in their urine (hematuria). Pus in the urine (pyuria) and bacteria in the urine (bacteriuria) are usually absent, unless there is a concurrent bacterial urinary tract or prostate gland infection. Dogs with BPH may have clear or pink-tinged prostatic fluid, which can be obtained by ultrasound-guided fine needle aspiration, by manual collection of the third fraction of the ejaculate or by prostatic massage. The fluid sample will be submitted for culture (to see if abnormal microorganisms can be grown) and for cytology (examination of the sample under a microscope). Dogs whose prostate is enlarged only because of BPH will have negative results from these diagnostic tests.
Abdominal radiographs (X-rays) of affected dogs may be recommended, especially if the dog is straining to defecate. Abdominal radiographs taken of a dog with BPH usually will reveal an enlarged prostate gland (prostatomegaly). However, they will not differentiate between the possible causes of the enlargement. Radiographs may also show upward (dorsal) displacement of the colon (large intestine) caused by the space-occupying nature of the enlarged prostate gland. Abdominal ultrasound can likewise reveal an enlarged prostate gland, without suggesting its cause. Cysts in the prostate may be detected on ultrasound, but in dogs with BPH the urethra will typically appear normal. The attending veterinarian may elect to perform an ultrasound-guided fine needle aspirate of prostate tissue. That sample can be submitted to a veterinary diagnostic laboratory for precise evaluation of the presence and cause of any prostatic disease.
A less used but quite advanced diagnostic technique, called retrograde urethrocystography, may be able to reveal a narrowing of the urethra as it passes through the prostate gland in dogs with BPH. This procedure is not yet widely available at local veterinary clinics but may be available at specialized referral centers and veterinary teaching hospitals.