The reproductive tract of the male (tom) cat consists of the penis, testes, scrotum, prostate and bulbourethral glands, and the ductus deferens (also called the vas deferens) (Fig. 44.1). The fetal testes are inside the abdomen; they descend through the inguinal ring into the scrotum at birth or shortly afterward. By 6 to 8 weeks of age, testes may be palpable in the scrotum although they may not permanently stay in the scrotum until 4 to 6 months of age. The hair-covered scrotum is divided by a thin wall into two cavities; each cavity contains a testis, epididymis, and the end of the spermatic cord. The structure of the feline testis is similar to most domestic animals with three major cell types:

The prostate of the cat is approximately 1 cm in length and covers the urethra near the neck of the urinary bladder. The prostate is androgen-dependent and atrophies after castration. Prostatic disease is rare in the cat, with only a few cases reports of tumors published.1,2 The bulbourethral glands are two small pea-shaped structures near the bulb of the penis. During ejaculation, spermatozoa from the epididymis are mixed with secretions from the prostate and bulbourethral glands. It is normal for a small proportion of spermatozoa to travel retrograde through the urethra into the bladder (Fig. 44.2). The urethra in the male cat is very narrow and shorter than in the dog.

The penis of the cat contains a vestigial os penis (5 mm in length). When not erect, the penis is completely enclosed within the prepuce. The glans of the penis of a mature tom cat is covered with 120 to 150 penile spines that are directed caudally. The spines are testosterone-dependent and start to appear at about 12 weeks of age, are fully developed at puberty, and are absent in neutered males, disappearing by about 6 weeks after castration (Fig. 44.3).

Spermatozoa are present in the testes by the age of 5 to 9 months, and full maturity of spermatogenesis occurs at 8 to 10 months of age.3 However, the actual age at which mating begins varies with physical condition, body size, and season. The onset of puberty is typically at 8 to 10 months of age and at a body weight of 2.5 kg or more. However, there is significant variation, with longhair breeds, such as the Persian, maturing more slowly than shorthair breeds, such as the Siamese. Tom cats probably have a normal breeding lifespan of 10 years or more.

Tom cats are attracted to estrous queens by vocalizing, odors, and behavior. A tom cat will approach a queen in estrus, touch noses, and then investigate the queen’s perineum. A flehmen reaction may be ­exhibited – ­sampling of the queen’s pheromones by the vomeronasal organ. The tom cat grasps the skin on the back of the queen’s neck and attempts to mount. The tom cat then treads on his back feet and slides down over the back of the queen, attempting to position for intromission. After intromission, the tom cat starts a series of pelvic thrusts, and ejaculation follows within 20 to 30 seconds. Semen is deposited in the posterior vagina. The tom cat then quickly jumps away to avoid being swatted by the queen. Once the queen’s postcoital behavior calms down (typically in 10 to 60 minutes), the tom cat will often try to grasp and mount again. A pair may breed several times until the tom cat is tired. Breeding usually occurs at night under natural circumstances.

After castration, mating behavior typically ceases, but may persist for years in some mature and experienced tom cats. This may include mounting of other cats or kittens, the owner’s legs, or soft inanimate objects. It is important to ensure the cat is not cryptorchid (see later). A rare cause of breeding behaviors in castrated male cats is a testosterone-secreting adrenal tumor.⁴ The behavior may also be attention seeking or due to a stimulus-poor environment. Ensuring adequate environmental enrichment and interactive time with the owner is often helpful. The behavior should not be rewarded, even inadvertently, by attempts at punishment. Interruption and distraction with another activity is likely to be more effective. Urine spraying may also persist after castration, although typically it resolves in the majority of cats. There is one report on the use of cyproheptadine (2 mg/cat, PO, every 12 hours) for the successful treatment of masturbation and urine spraying in a cryptorchid cat.⁵ For more on urine spraying, see Chapter 16: Behavior Problems.

Few problems affect the penis of cats; conditions found more commonly in other species, such as hypospadias and persistent penile frenulum, are rare in the cat. One case report of hypospadias in a 1-year-old Himalayan cat was associated with chronic cystitis.6 The hypospadias was surgically corrected, and the cat recovered fully. In another case report, a 1-year-old Persian cat presented for infertility was found to have dorsal deviation of the penis resulting from a persistent frenulum.⁷

A small number of cases of phimosis have been reported in the cat.^8–10 Phimosis is due to constriction of the preputial opening that prevents protrusion of the penis. Phimosis may be congenital or acquired secondary to trauma, inflammation, or neoplasia. The most common clinical signs are stranguria, pollakiuria, and vocalizing during urination; other clinical signs include dribbling urine, urinating outside the litter box, and inability to mate. The severity of clinical signs varies with the degree of narrowing. Diagnosis is made on physical examination by finding a small or inapparent preputial opening. In many cases, surgical correction of the defect is necessary.

The records of 10 cats diagnosed with phimosis treated at Michigan State University Veterinary Teaching Hospital were reviewed in one report.⁹ The mean age at presentation was 18.6 weeks (range, 8 weeks to 2.4 years). Two of the cats had other congenital defects (cryptorchidism, penile hypoplasia). Eight of the cats underwent surgical correction by a full thickness incision in the ventral aspect of the prepuce, with or without resection of a wedge of prepuce. A satisfactory outcome was achieved in seven cats, where long-term follow-up was available. In another study of eight kittens (<20 weeks old) presented to two veterinary medical teaching hospitals, six kittens had type 1 phimosis (generalized preputial swelling owing to urine pooling without penile-preputial adhesions) and underwent circumferential preputioplasty.¹⁰ Two kittens had type 2 phimosis (focal preputial swelling and urine pooling in the presence of penile-preputial adhesions) and underwent preputial urethrostomy. No postoperative complications were reported for kittens that underwent preputial urethrostomy. All kittens that underwent circumferential preputioplasty had some exposure of the tip of the penis immediately after surgery, which resolved over time.

Priapism is persistent abnormal erection of the penis in the absence of sexual stimulation, and may be caused by a variety of factors, such as spinal cord injury, trauma, neoplasia, and inflammation. It is rarely reported in the cat. Priapism may be confused with paraphimosis; however, paraphimosis is associated with a narrow preputial orifice or other preputial abnormalities. Without intervention, the penis may become dry and edematous, and even necrotic. Most cases in the cat require surgical management. In a report of seven cases, six patients were Siamese cats.¹¹ In four cases, priapism developed after unsuccessful attempts at mating even though three of the cats were castrated. Five were successfully treated with perineal urethrostomy, and histologic examination revealed thrombosis of the corpus cavernosum. Priapism was reported in a 1.5-year-old domestic shorthair cat after routine castration.¹² Two days after surgery, the cat developed pollakiuria and stranguria, as well as protrusion of the penis. The cat was successfully treated with perineal urethrostomy. Histology of the resected tissue revealed severe congestion of the corpus cavernosum, with organized thrombi and areas of necrosis. Another case of priapism was reported in a 2-year-old castrated male with feline infectious peritonitis (FIP).¹³ At necropsy, histologic examination of the penis revealed severe pyogranulomatous inflammation and fibrinoid necrosis of the corpus cavernosum.

Orchitis is rare in the cat, although occasionally bacterial orchitis has been reported. Clinical signs include scrotal swelling, pain, and redness. Bacterial orchitis is treated with a broad-spectrum antibiotic. Orchitis has also been reported as an uncommon manifestation of FIP;14 one case report was a cat concurrently infected with FIV.¹⁵ Scrotal swelling may be the only sign associated with FIP in affected cats, at least initially. The vaginal cavity around each testis is confluent with the peritoneal cavity so that fluid accumulating in the abdomen may also appear in the scrotum. Lesions in the testes are consistent with a chronic necrotic and fibrinous orchitis and fibrinous periorchitis with vasculitis.

Testicular neoplasia is uncommon in the cat. Examples of both Sertoli and interstitial cell tumors have been reported.^1,16–18 Neoplasia of testicular origin developing after castration has been reported in five cats.¹⁹ All cases involved interstitial cell tumors within the scrotal skin or the spermatic cord. The mean age at diagnosis was 9.6 years. Affected cats demonstrated sexual behaviors normally associated with intact males, such as urine spraying and aggression. Two cats had penile spines. The study authors suggest that care be taken during castration to avoid incising the tunica albuginea to avoid transplantation of small amounts of testicular tissue, and the subsequent development of tumors.