Introduction
The prostate is a lobed gland in male dogs located at the junction of the bladder and urethra. It contributes to the seminal fluid. The prostate gland normally increases in size and weight as male dogs age. The primary disorders of the prostate in dogs are benign prostatic hyperplasia (BPH), prostatic cysts, bacterial prostatitis, prostatic absceses and cancer (neoplasia). Of these, BPH and bacterial prostatitis are seen most frequently. However, while uncommon, prostatic neoplasia is among the most serious of prostate conditions in dogs.
The incidence of prostate cancer is similar in intact and neutered male dogs. The most common type of prostate cancer in dogs is adenocarcinoma, which seems to predominate in unneutered animals. Other reported tumor types include undifferentiated carcinoma, fibrosarcoma, leiomyosarcoma and squamous cell carcinoma, which tend to be more common in neutered dogs. Regardless of type, prostate tumors tend to invade surrounding tissue and are highly metastatic, commonly spreading to bone in the spine and/or pelvis and to regional lymph nodes. They also often metastasize to the lungs.
Symptoms of Prostatic Cancer in Dogs
Early Symptoms
Signs of prostate cancer largely mimic the signs of prostatitis and benign prostatic hypertrophy. They usually are chronic in nature, with a gradual onset, and are linked to the urinary tract. Affected dogs may show no signs at all. More often, they will have difficulty urinating (dysuria), will urinate (or try to urinate) frequently and in small amounts, will strain to urinate and defecate (stranguria/tenesmus), may be constipated from compression of the colon by the tumor and frequently will have blood in their urine (hematuria). They also commonly have a watery, bloody discharge that periodically drips from their penis (this is called a “serosanguinous” discharge).
Advanced Symptoms
Dogs with more advanced disease may show rear end lameness or other motor disturbances caused by metastasis of the cancer to bone, with accompanying pain. Affected dogs can be lethargic with little interest in playing or even eating, and they may hold their tails abnormally and slightly away from their hindquarters due to discomfort. They may have intermittent fever and often lose weight to the point of emaciation due to the inappetance that commonly accompanies cancer.
Dogs with prostate cancer can exhibit some, all or none of these clinical signs at varying stages of their disease. The median age of dogs at the time of diagnosis with prostate cancer is 10 years of age. If your older dog, whether neutered or not, exhibits any of these clinical signs, you should consult with a veterinarian at your earliest opportunity.