Chapter 90 Diseases of the Ovaries and Uterus
DISEASES OF THE OVARIES
Disorders of the Ovarian Cycle
Etiology
Disorders of the ovarian cycle are seen when ovarian secretion of estrogen and/or progesterone are abnormal. Hormonal abnormalities can be associated with cystic ovarian disease, ovarian dysgenesis, ovarian neoplasia, ovarian remnants, and secondary conditions that affect ovarian function. Ovarian cycle abnormalities usually manifest as abnormalities in reproductive events. The hormonal, physiologic, cytologic, and behavioral events of the normal estrus cycle are presented in Table 90-1.
Clinical Signs
Failure to Cycle or Persistent Anestrus
• Prolonged anestrus is defined as interestrous intervals of greater than 1 year in the bitch and 1 month in the cycling queen.
• Failure to cycle should be differentiated from “silent heat,” in which outward manifestations of estrus are not observed. This happens especially in young bitches in their first cycle.
• If clinical signs of endocrine disorders (hypothyroidism or hyperadrenocorticism) are present, these conditions should be pursued as an underlying cause (see Chapters 31 and 33).
• Basenji, Tibetan mastiff, and dingo breeds can have long interestrous intervals as a normal breed variation.
Short Interestrous Intervals
• Four months or less between ovarian cycles is considered abnormal as the uterus requires an adequate amount of time to repair and regenerate, permitting normal implantation on subsequent breedings.
Prolonged Estrus
• Estrus is considered prolonged if the signs persist greater than 35 days in the bitch and greater than 16 days in the queen.
• “Split heat” can be confused with prolonged estrus. In a split heat, proestrus ends and estrus does not begin until 2 to 4 weeks later, giving the false impression of prolonged estrus.
Diagnosis
Physical Examination
Examine the vulva to determine degrees of swelling and types of discharge that suggest various stages of the estrous cycle (see Table 90-1).
Vaginal Cytology Technique
• Insert a saline moistened cotton-tipped swab into the cranial vagina. Direct the swab dorsally through the vestibule, then redirect to advance the swab cranially. Avoid contact with the floor of the vestibule and vagina so that the clitoral fossa or urethra is not entered.
• Once removed from the vagina, roll the swab several times across the surface of a glass slide and allow to air dry.
Hormonal Analysis
Estradiol
• Typical serum concentrations are 5 to 10 pg/ml during anestrus, 10 to 100 pg/ml during proestrus. During estrus and diestrus, serum estrogen concentrations are often undetectable.
• Elevated serum estrogen concentrations are sometimes found in cystic ovarian disease, but this is not consistent.
Progesterone
• Parturition occurs at the end of diestrus when the serum concentration of progesterone falls below 1 to 2 ng/ml.
• The finding of increased progesterone concentrations in an animal suspected of prolonged anestrus indicates that a luteal cyst may be present, or that a normal estrus cycle occurred and was not clinically observed.
Treatment
Failure to Cycle or Persistent Anestrus
• Induction of estrus can be attempted, but success in inducing a fertile estrous cycle is unpredictable at best.
• The GnRH analogue, d-Trp6-GnRH (Decapeptyl), has been used to induce estrus in bitches and queens by giving 1μg/kg subcutaneously every 8 hours until estrus begins, and then half the dose q8h for an additional 3 days.
• Diethylstilbestrol has been used to induce estrus at 5 mg PO daily until 2 days after the onset of estrus.
• Estrus can be induced in the queen by exposure to 12 continuous hours of bright light per day. This results in estrus within 1 to 2 months.
• Porcine follicle-stimulating hormone given at 2 mg/cat IM daily has been used to stimulate estrus in cats.
Prolonged Estrus
• The most reliable means of treating follicular ovarian cysts is to rupture them manually during exploratory laparotomy, or to remove the ovaries completely.
• Medical induction of ovulation has been reported using GnRH (Cystorelin) at 2.2μg/kg IM once daily for 3 days.
• In the queen, ovulation can be induced mechanically. Insert a lubricated small rectal thermometer (or another similar probe) into the vagina and manipulate in a pulsatile fashion for about 5 seconds at 15-minute intervals 4 to 5 times. This mimics copulation and causes a surge in luteinizing hormone (LH) that results in ovulation in most queens.
Ovarian Remnant Syndrome
Etiology
• Ovariohysterectomized dogs and cats exhibiting clinical signs of estrous are likely to have ovarian remnant syndrome, which is due to incomplete removal of all ovarian tissue at the time of ovariohysterectomy.
Clinical Signs
Clinical signs of estrus typically reoccur between 1 and 3 years following ovariohysterectomy.
Diagnosis
• The finding of increased serum progesterone concentrations that are consistent with diestrus in a female with clinical signs of estrus indicates the presence of ovarian tissue.
• Evaluation of LH levels will also confirm the presence of ovarian tissue in a spayed female. High serum concentrations of LH are normal in a spayed female due to lack of negative feedback from the ovaries. A low LH level is an excellent indicator that a spayed female has ovarian tissue present.
Ovarian Neoplasia
Etiology
• The more commonly reported tumors in dogs include granulosa cell tumors (which can cause hyperestrogenism), adenoma, adenocarcinoma, and germ cell tumors such as teratoma and dysgerminoma.
• In cats, granulosa cell tumors, which are more often malignant than in the dog, are most common. Teratoma has also been reported.
Clinical Signs
• Functional granulosa cell tumors can cause signs of hyperestrogenism (persistent estrus, gynecomastia, anemia, bone marrow suppression, dermatologic signs) or can underlie infertility in the bitch or queen.
Diagnosis
• Clinical signs of hyperestrogenism, palpable abdominal mass, or abdominal effusion aid in the diagnosis.
• Perform a complete blood count, serum chemistry profile, and urinalysis to investigate effects of hormonal imbalances.
• Measurement of serum concentrations of estradiol are not always reliable due to fluctuations in hormone secretion and cannot effectively differentiate between a functional ovarian neoplasm and ovarian remnant syndrome.
• Abdominal radiography can reveal a mass effect in the region of the kidneys. Also perform thoracic radiography to evaluate for metastasis.
• Ovariectomy and histopathologic examination provide a definitive diagnosis (see Chapter 91). Examine regional lymph nodes and obtain tissue samples for histopathology at the time of exploratory laparotomy.
DISEASES OF THE NON-PREGNANT UTERUS
Pyometra
Etiology
• Progesterone normally causes endometrial gland growth and fluid secretion, as well as decreased myometrial contractility and retention of uterine contents. These hormonal effects are necessary to sustain pregnancy, and serum progesterone concentrations are normally elevated throughout diestrus, finally decreasing to below 1 to 2 ng/ml just prior to parturition.
• The non-pregnant uterus typically goes through the same hormonal cycle as a gravid one, and cystic endometrial hyperplasia (CEH) can occur.
• Bacteria from the lower genital tract can colonize the uterus leading to infection. The most commonly isolated bacteria from pyometra are Escherichia coli.
Risk Factors for Pyometra
• Previous treatment with progestins such as megestrol acetate predisposes the patient to the development of pyometra. Progestins are sometimes used in bitches to suppress estrus and are used for dermatologic and behavioral conditions, although their use should be minimized.
• Pyometra may also be more common in bitches treated with estrogens, as is sometimes done to prevent pregnancy in mismating incidents. Estrogens potentiate the uterine effects of progesterone.
Clinical Signs
• Because the disorder is progesterone dependent, clinical signs should begin sometime after the onset of diestrus. Therefore, a history of estrus within the preceding weeks is common. Although progesterone is needed to initiate CEH and pyometra, the condition can persist after diestrus has ended, and some cases are diagnosed several weeks after progesterone would be expected to be elevated.
• Vaginal discharge is a common clinical sign. When vaginal discharge is observed, the pyometra is said to be “open,” referring to patency of the cervix.
• Pyometra in the absence of vaginal discharge is referred to as “closed,” meaning that uterine contents are unable to drain through a closed cervix. Whether the cervix is actually patent or not in a given case of pyometra is usually not investigated, and a true difference between these two classifications may not exist.
• Polyuria is a common finding in dogs with pyometra and is thought to be a bacterial endotoxin effect on the renal urine concentrating mechanism. Polyuria is not noted in cats with pyometra.
Diagnosis
History and Physical Examination
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