Several reproductive diseases can affect male dogs. This section discusses the most common of these disorders.
Cryptorchidism is a failure of one or both testicles to descend into the scrotum. It is the most common disorder of sexual development in dogs. The condition has a genetic basis and can be inherited from either parent. If both testicles are affected, the dog is sterile. Because the retained testicles still produce male hormones, these animals have normal mating behavior. If only one testicle is retained (unilateral cryptorchidism), the dog can still mate normally, as the one normal testicle will produce normal sperm. Because the condition is inherited, cryptorchid dogs should not be used for breeding. This condition occurs in all breeds but is commonly seen in the Toy and Miniature Poodle, Pomeranian, Dachshund, Chihuahua, Maltese, Boxer, Pekingese, English Bulldog, Miniature Schnauzer, and Shetland Sheepdog. Affected animals should be neutered due to an increased risk of developing testicular cancer.
Inflammation of the Testes and Epididymis
Short-term inflammation of the testis or epididymis may be caused by injury or infection. Signs are pain and swelling of the testes, epididymides, or scrotum. There may be wounds or other abnormalities in the scrotal skin. The disease is diagnosed by physical examination, ultrasonography, and laboratory tests. Treatment is difficult unless the cause of the inflammation can be identified. Application of cool water packs may decrease testicular damage caused by inflammation. If there is a bacterial infection, antibiotics will be administered. If the cause is an immune disorder, medications that suppress the immune system may be administered. When maintaining fertility is not important, castration is a reasonable treatment choice for inflammation of the testes or epididymes due to any cause.
Longterm inflammation of the testis or epididymis may follow short-term inflammation, although in some cases there is no history of testicular inflammation. Many dogs do not have any signs of the disease except for infertility; however, decrease in size or softening of the testes may be present. Non-inflammatory causes of this disease include previous exposure to excessive pressure, heat, cold, or toxic agents. Hormonal causes are also possible. The diagnosis and treatment is as described above for the short-term condition.
Inflammation of the Penis and Prepuce (Balanoposthitis)
Balanoposthitis is inflammation of the penis or preputial cavity (the skin on the dog's belly that covers the penis). Mild balanoposthitis is present in many sexually mature dogs and it resolves spontaneously without any treatment. There are several causes of more severe balanopos-thitis, including allergies, trauma, foreign objects, bacterial infection, and phimosis (a condition in which the prepuce cannot be drawn back to expose the penis). The most common sign is yellow-green discharge at the tip of the penis or prepuce. Swelling of the prepuce and pain are rarely present except in cases of trauma or foreign objects. The disease is diagnosed by physical examination and laboratory tests. Treatment includes correcting any predisposing factors, clipping long hair away from the opening of the prepuce, and thorough flushing of the preputial cavity with a mild antiseptic or sterile saline solution. In the case of a bacterial infection, your veterinarian may prescribe an antibiotic. Neutering will diminish preputial secretions.
Paraphimosis, or the inability to completely retract the penis into the preputial cavity usually occurs after erection. It is seen most often after semen collection or breeding. The skin at the preputial opening traps the extruded penis, impairing blood circulation. Other causes of paraphimosis include a constricting band of hair at the preputial opening or other trauma to the penis. Paraphimosis is a medical emergency because the exposed penis quickly becomes swollen (due to accumulation of fluid), dry, and painful. If recognized early, before severe swelling and pain develop, paraphimosis is easily treated. The treatment consists of gentle cleansing and lubrication of the exposed penis. The penis is replaced inside the prepuce and the swelling resolves once circulation is restored.
Phimosis is the inability to expose the penis and may be due to an abnormally small preputial opening. It may be hereditary or acquired as a result of trauma, inflammation, or bacterial infection. The signs are variable. Usually, the problem is unnoticed until the dog attempts to mate and is unable to copulate. Diagnosis is established by physical examination of the prepuce and penis. Treatment depends on the severity of the phimosis and the intended use of the dog. If the dog is not used for breeding, treatment probably is not needed, although neutering could be considered to prevent arousal.
Disorders of the Prostate
The prostate gland is located within the pelvis behind the bladder. The size of the prostate is determined by the hormone dihydrotestosterone in mature dogs. The prostate gland is not required for sperm production but it is important for successful breeding. The prostate gland provides the major part of the fluid in the ejaculate and is important in nourishing the sperm cells and increasing their movement.
Diseases of the prostate gland are common in dogs that have not been neutered and include enlargement of the prostate (benign prostatic hyperplasia), bacterial infection, abscesses, cysts, and tumors. These disorders cause enlargement of the prostate gland. Additional signs, such as fever, malaise, poor appetite, stiffness, and pain in the belly, are often due to bacterial infections or presence of tumors. Prostatic diseases are diagnosed by physical examination, x-rays, ultrasonography, and blood and semen tests.
Enlargement of the Prostate (Benign Prostatic Hyperplasia)
Enlargement of the prostate is the most common prostatic disorder. It is caused by male hormones. It is found in almost all unneutered dogs over the age of 6 years. There may be no signs, or straining to defecate and blood in the urine may occur. Neutering is the preferred treatment. Reduction in the size of the prostate usually follows within a few weeks of the surgery. In dogs used for breeding, medication to decrease the size of the prostate may be helpful.
Inflammation of the prostate gland may be due to bacterial infections and can result in abscesses. The signs are similar to those of prostate enlargement see Reproductive Disorders of Dogs: Enlargement of the Prostate (Benign Prostatic Hyperplasia). In addition, malaise, pain, and fever are common. Dehydration and shock may occur in severe cases of prostatic abscesses. The disease is diagnosed by physical examination, x-rays, and blood tests. Longterm bacterial prostatitis may cause no signs except for recurrent urinary tract infection. Prostatitis is treated by administration of antibiotics and may require prolonged treatment. Neutering will speed recovery.
Prostatic and Paraprostatic Cysts
Large cysts are occasionally found within or near the prostate gland. The signs are similar to those seen with other types of prostatic enlargement and usually become apparent only when the cyst reaches a size sufficient to cause pressure on other organs. Large cysts may result in abdominal distention. Drug treatment may be ineffective. Your veterinarian may attempt to drain the cyst by using ultrasonography as a guide. The treatment of choice for large cysts is surgical removal. Neutering alone is unlikely to provide sufficient benefit but may be recommended after the cyst has been removed.
Prostate cancer is a serious, yet uncommon, disorder in dogs. Neutering does not protect against future development of prostate cancer in dogs. The signs are similar to those of other prostatic diseases. Pain and fever may be present. Furthermore, the cancer may spread to other tissue and organs. There is no effective curative treatment. Consultation with a veterinary oncologist (cancer specialist) is recommended.
Last full review/revision July 2011 by Cheri A. Johnson, DVM, MS, DACVIM (Small Animal); Brad E. Seguin, DVM, MS, PhD DACT; Autumn P. Davidson, DVM, MS, DACVIM; Fabio Del Piero, DVM, DACVP, PhD; James A. Flanders, DVM, DACVS; Mushtaq A. Memon, BVSc, MS, PhD, DACT; Paul Nicoletti, DVM, MS, DACVPM; Robert C. Rosenthal, DVM, PhD, DACVIM (Small Animal, Oncology), DACVR (Radiation Oncology)