Problem Definition and Recognition
This chapter describes abnormalities of the external genitalia that are detectable by physical examination. Abnormalities of the vulva and mammary glands constitute the female external genitalia, while the scrotal sac and prepuce constitute the male external genitalia.
Abnormalities of the female external genitalia are listed in Table 36-1.
Small Size. A relatively small vulva can result from immaturity, neutering at a young age, or hypoplasia. A small vulva is of little clinical consequence in most bitches, but it can cause perivulvar dermatitis.
Enlarged (Swollen). A swollen vulva may be turgid, soft, or pitting. The vulva is swollen and turgid during proestrus, occasionally with vaginitis or in association with perivulvar dermatitis. The vulvar swelling during proestrus is the result of rising estrogen from growing ovarian follicles. The turgidity decreases with the onset of estrus due to declining estrogen and rising progesterone levels. In the pregnant bitch, the vulva swells in late gestation when estrogen levels increase in preparation for parturition. Pitting edema of the vulva may be due to hypoalbuminemia. Diagnosis of the cause of generalized vulvar swelling can usually be made by establishing the estrous cycle stage, by physical examination, and by vaginal cytologic examination. If pitting edema of the perineal area is present, a complete blood count, blood chemistry profile, and urinalysis are indicated.
Vaginal Mass. A mass protruding from the vulva may be a vaginal prolapse, a vaginal neoplasm, or a prolapsed uterus. These diseases are common in dogs and very rare in cats.
Vaginal prolapse (vaginal hyperplasia) occurs during proestrus or estrus, principally in young, large-breed dogs. The edematous vaginal mucosa protrudes through the vulvar lips. The amount of vaginal tissue that prolapses is variable, from just the ventral vaginal floor to the entire vaginal circumference up to the cervix. It is described in three degrees. First-degree vaginal prolapse involves just the vaginal floor with no tissue protruding through the vulvar lips. Second-degree prolapse involves the cranial vaginal floor and lateral walls protruding through the vulvar lips as a tongue-like mass. Third-degree prolapse involves the entire vaginal circumference protruding through the vulvar lips forming a donut-shaped mass. The bitch’s behavior is normal, except for possible licking at the mass and difficulty urinating. The condition typically regresses spontaneously and resolves at the end of estrus; however, it tends to recur with each estrous cycle. If spontaneous regression is elected for treatment, the vaginal tissue should be kept clean from debris and feces, and an Elizabethan collar may be necessary to prevent irritation and self-mutilation of the vagina while it is exposed.
|b. Neutering at a young age|
|2. Generalized swelling|
|c. Perivulvar dermatitis|
|e. Late gestation edema|
|3. Vaginal mass|
|a. Vaginal prolapse|
|b. Vaginal tumors|
|c. Prolapsed uterus|
|a. Anovulvar cleft|
|b. Vulvar stenosis|
|c. Clitoral hypertrophy|
|2. Mammary hypertrophy/hyperplasia|
Vaginal tumors may also protrude through the vulvar lips. Differentiation from vaginal prolapse can usually be made from history of estrous cycle stage, physical appearance of the mass, and cytological examination of impression smears made from the mass; biopsy is occasionally required. The most common vaginal tumor is a leiomyoma, which is a benign and often pedunculated tumor of the vaginal smooth muscle. Other common benign tumors are fibromas, lipomas, and polyps. Diagnosis is usually based on excisional biopsy. Transmissible venereal tumors, which are common in some areas, can be diagnosed on impression smear by the characteristic uniform population of large round cells. The most common malignant tumor affecting the vagina is a transitional cell carcinoma arising from the urethra and invading the vagina at the urethral papilla. Transitional cell carcinomas in this location produce dysuria (see Chapter 32) as the predominant clinical sign and are visualized by vaginoscopy.
A prolapsed uterus is uncommon in both dogs and cats. Prolapse occurs at or within 48 hours of parturition or abortion, when the cervix is open. Diagnosis is made from the history of recent parturition and physical examination. The entire uterus or only one horn may prolapse. Depending on the severity and duration of the prolapse, clinical signs vary from straining and restlessness to hypovolemic or septic shock. In contrast to vaginal prolapse, uterine prolapse rarely recurs after the uterus is returned to its normal position.
Congenital Abnormalities. An anovulvar cleft results from incomplete closure of the skin from the dorsal vulvar commissure to the anus. Vulvar stenosis occurs at the junction of the vestibule with the labia as a result of incomplete fusion during fetal development.
Clitoral hypertrophy occurs in hermaphrodites, pseudohermaphrodites, normal females receiving androgenic drugs, secondary to irritation of the clitoral fossa, and rarely, animals with hyperadrenocorticism. Clitoral hypertrophy often persists after the inciting cause has been removed. If causing discomfort, evidenced by pain or excessive licking of the area, clitoridectomy is the treatment of choice.
Mammary Gland Abnormalities
Mammary gland enlargement can be due to milk accumulation, hypertrophy, inflammation, or neoplasia.
Galactosis. Galactosis refers to mammary accumulation of milk. Such accumulation is normal in advanced pregnancy and lactation. During weaning, in pseudopregnancy, and occasionally at the time of whelping, such accumulation may increase to the point that the mammae become painful and warm. There are no signs of systemic illness, and the white blood cell count is normal. Diagnosis is made from the history, physical examination, and cytologic examination of mammary fluid. Fluid expressed from the teats will look like milk; microscopically it contains variable numbers of neutrophils and macrophages with engulfed milk fat. Treatment is unnecessary in mild cases.