Chapter 24 INFERTILITY, ASSOCIATED BREEDING DISORDERS, AND DISORDERS OF SEXUAL DEVELOPMENT
Before an investigation is begun into the potential causes of infertility in a bitch, the male should be assessed. The primary reason for evaluating the male before the female is that males are so much easier to study. The normal male is continuously fertile (i.e., continuously producing sperm). The female is usually fertile only 1 to 3 weeks per year. The easiest and usually most reliable method of establishing male fertility is a review of the male’s previous breeding history. Any male that has sired one or more litters in the preceding 1 to 4 months usually can be assumed to be fertile. It is also helpful to know if the male sired any litters at the time the bitch in question was in heat and bred. However, even with positive responses to these inquiries, the fertility of the male should be demonstrated with a semen analysis.
All active stud dogs should be tested for brucellosis every 6 months. Less active studs should be checked yearly and immediately prior to use. A male that has not sired a litter or that has sired litters in the past but not in the preceding 6 to 12 months must be viewed with suspicion. Whenever the male’s fertility is questionable, the owner of the bitch has three main alternatives: (1) have a semen analysis and Brucella titer performed on the male; (2) use an alternative, proven sire on the next heat; or (3) have the bitch evaluated, realizing that she may not be at fault.
A normal result on semen analysis is a major step toward ensuring that the male is not at fault. Abnormal semen or inability to obtain an ejaculate leaves suspicion directed at the male. Any normal male may have one or two abnormal semen analyses, but each abnormal study increases the likelihood of male infertility. In addition, males can have sperm that appear morphologically normal but that may not be capable of fertilization. Sophisticated studies on sperm function are not yet widely available in small animal reproduction. In any case, semen analysis is typically simple, safe, and inexpensive.
Infertility or apparent infertility problems in the bitch are common. Veterinary advice is often sought if a bitch fails to conceive, if she fails to exhibit “normal” breeding behavior, when her cycles appear to be unusual, or for myriad other disturbances. “Infertility,” therefore, is a huge category comprising a long list of anatomic, physiologic, and behavioral problems as well as a number of apparent husbandry misunderstandings. Also, if a bitch has earned a championship or other important title, a demand for puppies, as well as their value, are ensured before any attempt is made at breeding.
Before the bitch is examined by the veterinarian, the various potential causes of infertility must be reduced to a workable number. In other words, the differential diagnosis for most infertility disorders is established by obtaining a thorough history from the owner. The initial history should include information about how well the owners know the bitch (e.g., does she live indoors with them, or 200 miles away at a hunt club?). Is she housed alone, with another bitch or bitches that recently completed ovarian cycles, with one or more ovariohysterectomized bitches, or with males? Is she of normal height and weight for her breed and her line? Is she receiving any medication, and is she well or ill?
To avoid the time-consuming chore of asking all the questions that help establish a problem list, differential diagnosis, and diagnostic plan, the veterinarian should have clients complete a questionnaire (Table 24-1). This list does not necessarily provide a complete background on every bitch, nor does it always provide the information needed to determine a diagnosis, but it does include the basic questions that must be answered to establish a foundation from which to work. Also, items can always be forgotten when reviewing a case history during a busy workday, and the question sheet helps avoid this problem.
Small dogs reach sexual maturity at a younger age than large dogs. The onset of the pubertal (first) estrus in the bitch has been reported to occur at ages ranging from 6 to 23 months, with mean ages in different study populations of 9.6 to 13.9 months (Wildt et al, 1981; Johnston, 1991). Virtually all healthy bitches, therefore, begin ovarian cycles by 24 to 30 months of age.
Because first and second cycles may be irregular, unusual, short, or long (Wright and Watts, 1998), infertility evaluations are delayed in most dogs until 24 to 30 months of age. Just knowing the age and breed, therefore, can help the clinician decide how aggressive to be diagnostically. Toy Poodles may benefit from evaluation earlier in life than Bull Mastiffs. Each breed does have distinct average interestrous intervals, but the interval varies within a breed. As a general rule, almost all breeds cycle once every 4.5 to 10 months. The African breeds cycle once yearly. The remainder of the critical factors in an infertility evaluation are described under each major subheading.
As with any serious problem, the area of concern should be the last to be evaluated on physical examination. This approach ensures that each bitch receives a complete physical examination prior to an evaluation of the reproductive tract. The items specifically mentioned in this section involve the reproductive tract, but this should not suggest that a thorough examination be abbreviated in order to evaluate these areas.
Examination of the reproductive tract usually begins with an external inspection of the vulva, which involves checking size and conformation and looking for any discharge. A small, immature vulva or one that is recessed under a fold of tissue, owing to body type or obesity, may impede normal breeding. An obese bitch is prone to perivulvar dermatitis. A swollen turgid vulva is suggestive of proestrus, and one that is swollen and flaccid may be consistent with dermatitis, estrus (standing heat), or approaching parturition.
The bitch in anestrus or diestrus usually has no vaginal discharge. A bloody discharge is most suggestive of proestrus, estrus, separation of the placental sites, or severe vaginitis. Greenish black or dark bloody vaginal discharges are associated with placental separation and postpartum “lochia.” Reddish brown, yellowish, or grayish, thick, creamy, malodorous vaginal discharges are often seen in open-cervix pyometra, metritis, or severe vaginitis. Straw-colored vaginal discharges are sometimes seen when bitches are in estrus. Clear mucus can precede parturition and is rarely worrisome. A vaginal cytology specimen should be an integral part of any reproductive examination, because such specimens are easy to obtain, inexpensive, and informative. Vaginal cytology should be performed for any bitch with a vaginal discharge.
A digital examination of the vaginal vault should be performed routinely on any bitch examined for breeding soundness. If a culture or cytology specimen is needed, it should be obtained prior to the digital examination. Most bitches are easy to examine. A gloved, lubricated index finger should pass easily into the vaginal vault, allowing assessment of the lumen, the urethral opening, and the size and shape of the clitoris. Masses, foreign bodies, strictures, painful vaginitis, or abnormal tissue bands all prevent easy and painless examination.
If the digital examination result is abnormal but inconclusive, vaginoscopy can be performed for a more thorough evaluation. An otoscope or a vaginal speculum provides an extremely limited view of the vaginal vault and is of little value in most clinical situations. Pediatric proctoscopes are easy to use for vaginoscopy (Fig. 24-1), are relatively inexpensive, and can be used in all but the smallest of miniature breeds. An endoscope is a more expensive but smaller diameter alternative. In most breeds a small-diameter pediatric proctoscope can be used, which provides far better visualization of the area than an otoscope. If vaginoscopy is performed, the clinician must be knowledgeable about the changes in the appearance of the vaginal mucosa associated with each phase of the estrous cycle (Table 24-2).
FIGURE 24-1 A and B, Vaginoscopy can be performed with a pediatric proctoscope. The instrument is easily passed into the vaginal vault for a thorough inspection. Despite its length, the pediatric proctoscope does not always allow visualization of the cervix, which illustrates the futility of using an otoscope for this procedure.
The mammary glands should be palpated. The primary concern is the presence of mammary tumors, although the glands can also be checked for evidence of lactation, mastitis, inverted teats, or benign nodules. The ventral midline can be checked for evidence of a surgical incision, which might suggest that the bitch has undergone ovariohysterectomy.
A rectal examination ensures that the pelvic canal has been assessed for previous fractures or other unsuspected abnormalities. Compression of the pelvic canal is a potential cause of dystocia and, less commonly, inability to breed. An attempt can be made to palpate the vagina ventrally, although this organ would have to be extremely abnormal to reveal anything suspicious on palpation.
Improper management practices are the cause of a large majority of apparent infertility problems. A bitch that is bred or attempted to be bred at incorrect times may be completely normal. She may fail to conceive as a result of being brought to the male when she is not fertile.
In the clinical evaluation of the infertile bitch, one underlying question is her overall health status. Some investigators have recommended complete blood counts, chemistry panels, urinalysis, and thyroid and adrenocortical function studies as initial steps in the evaluation of a potentially infertile bitch (Johnston, 1980; Johnston et al, 1982; Lein, 1983). Others have suggested that, “It is unethical and unprofessional to perform unnecessary tests without discussion with the owners as to the real value and cost of these investigations” (Wright and Watts, 1998).
We do not usually use extensive diagnostic testing unless the history or physical examination (or both) dictates that aggressive diagnostic testing is warranted. The bitch that appears healthy to an owner, that appears healthy on physical examination, and that has normal ovarian cycles does not have thyroid failure or adrenocortical disease and rarely has other significant organ disease. Therefore a complete blood count (CBC), a urinalysis, and a blood urea nitrogen (BUN) determination provide a sufficient database. Nonetheless, this approach depends on the completion of a thorough history and a competent physical examination. If abnormalities are identified through the history or physical examination, appropriate testing can then be done that may clarify the nature of the problem or specifically demonstrate the cause of infertility.
INFERTILITY IN THE BRUCELLA-NEGATIVE BITCH THAT HAS NORMAL OVARIAN CYCLES, NORMAL INTERESTROUS INTERVALS, AND THAT ALLOWS BREEDING (Fig. 24-2
Because the average proestrus lasts 9 days and the average estrus 7 to 9 days, commonly used management strategies succeed in the average bitch. The average bitch also has a clear, straw-colored vaginal discharge at the onset of estrus. However, if a “traditional” breeding protocol fails to result in conception, a new approach to breeding management may prove successful, and this is our initial approach to an “infertility problem.”
As the initial approach to an apparently normal bitch that fails to conceive, the veterinarian should recommend that the owner adopt a reliable breeding schedule while simultaneously monitoring follicular function and the time of ovulation. In this manner, if the problem is management related, it is corrected. If the problem is physiologic, it may be identified and treated appropriately.
The proposed breeding schedule is aimed at better understanding the estrous cycle of the individual bitch in question. It is important to realize that in the “normal” bitch, proestrus can be as brief as 1 to 2 days or as long as 25 days. Correct identification of day 1 of proestrus depends on an owner correctly detecting the first day of vaginal bleeding. Estrus (standing heat) can have a duration of 2 to 20 days. The recommendation, therefore, is to bring the bitch to a dominant male for evaluation of her behavior beginning on the second, third, or fourth day of proestrus and to continue to do so daily or every other day until diestrus is demonstrated both by her behavior and by vaginal cytology. If the male attempts to mount and the bitch is receptive, breeding should be allowed, regardless of the apparent timing in the ovarian cycle.
It is wise to have someone hold the male and another person attend to the bitch. The dogs are allowed to interact for 5 to 15 minutes so that the bitch’s response to the stud can be assessed. One is looking for evidence of standing heat. If the male is not the stud to be used in the actual breeding, the handlers must prevent mating. The handlers are also present to prevent fighting, which occasionally occurs.
Once the bitch displays standing heat, she should be bred on that day and every 2 to 4 days thereafter until she refuses to breed. In the context of this discussion, daily or every other day breeding is recommended because concern about infertility should not be complicated by uncertainty over whether breeding was occurring on appropriate days. Breeding is continued on this schedule, regardless of the duration of standing heat, the color of the vaginal discharge, the day of the cycle, or the interpretation of a vaginal cytology smear. This program ensures that viable sperm are present when eggs become available for fertilization. Bitches known to have a prolonged standing heat should be bred every 4 days until cytologic or behavioral diestrus is confirmed.
If a bitch is bred only on specific predetermined days of her cycle (counting from the first day that vaginal bleeding is detected), several potential problems exist. The most common recipes are breeding on days 10 and 12, 11 and 13, or 11 and 15. If proestrus lasts 4 days and estrus 5 days, breeding will be attempted when the bitch is in diestrus and no longer likely to be receptive or, if receptive, no longer fertile (some healthy bitches allow breeding during the first 1 to 3 days of diestrus as defined by vaginal cytology).
If a bitch is in proestrus for 16 days and estrus for 10 days, ovulation is likely to begin on day 19 or 20 and fertilization on days 22 through 26. If she was bred (artificially inseminated because natural breeding would not have been allowed by the bitch) on days 10 and 12, few if any sperm would be alive when fertilization takes place (see Fig. 24-6). Forced mating or artificial insemination or both may be performed in an attempt to ensure that breeding occurs on the predetermined dates, only to have the bitch later appear infertile, with no consideration given to the fact that she was bred on the wrong dates. Forced breeding is never acceptable and should be a clue that errors in management are likely.
Some bitches refuse a particular male or, less commonly, refuse mounting attempts by any male despite correct recognition of estrus. Preferences for particular mates have been documented in the bitch (Freshman, 1991). Three possible explanations for this frustrating dilemma are (1) the male has been brought to the bitch for mating, and she is dominant to him when she is at her home (the bitch does not allow submissive males to breed); (2) the male is submissive to the bitch in standing heat, regardless of the environment and regardless of the apparent relationship between these dogs at other times (Freshman, 1991); and (3) the bitch is housed with a bitch dominant to her and the other female may interfere with normal breeding behavior.
Like behavior, follicular function can be easily and inexpensively monitored. The owner should be taught how to obtain vaginal smears and then instructed to begin obtaining smears on the first day of proestrus, continuing daily until at least 4 to 5 days after the onset of behavioral or cytologic diestrus. Vaginal cytology is a reflection of peripheral estrogen concentrations, which in turn reflect follicular function. Vaginal smears identify the approximate days of estrus and can be used to definitively identify the beginning of diestrus (Olson et al, 1984). One can count back 6 days from day 1 of diestrus to the first likely day of ovulation and/or count back 1 through 4 days for the time of greatest fertility (see Chapter 19). Recognizing that viable sperm can survive approximately 4 to 7 days in the uterus after breeding, the veterinarian can determine if the breeding dates were optimal for fertilization. If not, the bitch should be managed differently to better coordinate breeding with fertilization. If the breeding dates were optimal, management problems can be excluded from the list of causes of infertility.
The results of vaginal cytology can be reliable and helpful. However, to enhance evaluations, serial serum progesterone concentrations should be determined as the bitch progresses through proestrus and into estrus (see Chapter 19). Frequent serial progesterone assessments allow identification of the first day that the concentration rises above 2 ng/ml, which should coincide closely with the onset of behavioral estrus and the luteinizing hormone (LH) surge (Hegstad and Johnston, 1992). If an enzyme-linked immunosorbent assay (ELISA) in-hospital kit is used for the tests, the progesterone concentration usually is estimated as less than 1 ng/ml, greater than 1 to less than 5 ng/ml, and greater than 5 ng/ml (Manothaiudom et al, 1995). Breeding is recommended 4 days after the serum progesterone concentration is greater than 1 ng/ml as measured with these kits. Optimal breeding dates are 4 and 6 days after the rise in the serum progesterone concentration. Vaginal endoscopic evaluation of the bitch several times during proestrus and into estrus can also be informative (see Chapter 19 and 20) (Lindsay, 1990).
The question regarding ovulation cannot be answered with testing completed during proestrus or estrus. Vaginal cytologic identification of the first diestrual day offers an indirect method of determining an approximate ovulation date, as previously described. However, a more precise determination can be made by measuring the plasma progesterone concentration daily or on alternate days. Ovulation begins 2 to 4 days after the progesterone concentration rises above 2.0 ng/ml (see Fig. 19-15). Again, these values do not confirm that ovulation took place, because progesterone is initially derived from luteinized follicles; that is, the serum progesterone concentration increases prior to actual ovulation. The initial rise does not confirm that ovulation occurs.
If the veterinarian wishes to determine whether a bitch ovulates, daily vaginal cytology smears can be used to identify day 1 of diestrus, and that information can be coupled with measurement of the plasma progesterone concentration obtained between the 10th and 20th day of diestrus. During the initial few weeks of diestrus, the plasma progesterone concentration should be greater than 3 ng/ml and usually is 10 to 50 ng/ml. Concentrations into the ranges mentioned can be attained only by progesterone secretion from functioning corpora lutea (excluding exogenous sources), which exist as a result of previous ovulation. Normal diestrual progesterone concentrations, therefore, are consistent with ovulation and proper luteal function.
Breeding practices need to be reviewed as potential problem areas. For example, it is not known whether tranquilization or the stress of shipping can interfere with ovulation or early pregnancy (Wright and Watts, 1998). These factors could be a cause of “acquired infertility” and are worth avoiding during one cycle to see if the infertility problem can be resolved by keeping the bitch at home and having her bred locally.
Furthermore, if an owner never observes a breeding because the bitch is always being shipped to the male, only secondhand information about mating is available. The owner should be encouraged to have the bitch bred locally so that breedings can witnessed. This is the most reliable means of minimizing stress and ensuring that unsuspected problems are identified. For example, if outside ties persistently occur, an anatomic problem in the vaginal vault may be preventing penetration by the male but may not be observed or reported.
All previously or currently used medications should be noted. Previous use of gonadotropins may have long-term deleterious effects on pituitary function. Previous progesterone or estrogen administration may result in subclinical cystic endometrial hyperplasia (CEH), with infertility being the only outward effect seen by the owner or veterinarian.
Most reviews concerning infertility in the bitch include discussion of hypothyroidism, a condition often described as common and as producing such signs as persistent anestrus, prolonged interestrous intervals, and prolonged proestrus, although some bitches demonstrate normal reproductive activity, pregnancy, and parturition (Johnston, 1980). However, only one bitch has been described in the veterinary literature since 1989 that had thyroid insufficiency and related ovarian disease (Johnston, 1989).
Hypothyroidism is an overdiagnosed endocrine disorder in veterinary practice. The diagnosis should always be viewed with suspicion, not because the disease does not exist but simply because many dogs treated for the disease are not so afflicted. If a bitch is being treated for hypothyroidism, the veterinarian must decide whether that diagnosis was correct and then whether thyroid replacement medication should be discontinued (see Chapter 3).
Management problems are the most common cause of apparent infertility in the bitch with a normal cycle (Johnston, 1980; Soderberg, 1989; Freshman, 1991). Veterinarians should remember to evaluate the male before embarking on the somewhat involved task of assessing the bitch. The entire question regarding proper management of an individual bitch can be answered through the relatively inexpensive approach of obtaining a thorough history, with corrections made, as needed, in past incorrect practices; behavior observation; review of vaginal cytology results; and monitoring of plasma progesterone concentrations. This approach answers the following questions: (1) how is the owner managing this bitch? (2) when does standing heat begin? (3) how long does standing heat persist? (4) what is the first day of true diestrus? (5) when is the bitch truly fertile? (6) what are her ideal breeding dates? (7) does she ovulate? (8) when does she ovulate? and (9) does she have the luteal function necessary to support pregnancy?
Brucella canis classically causes abortion late in gestation (see Chapter 26). In addition, the organism may render a bitch infertile or may cause resorption of fetuses early in gestation. B. canis infection can also result in ill or stillborn puppies (Olson et al, 1983). All bitches in active breeding programs should be repeatedly evaluated for canine brucellosis. The rapid slide agglutination test (Canine Brucellosis Diagnostic Test; Pitman-Moore, Washington Crossing, NJ) is an excellent screening test. False-negative results are unlikely, and a negative result can be trusted. Bitches that test seropositive should be retested with the tube agglutination method, because false-positive results do occur (Johnston, 1980).
Bacterial infections have been implicated as a cause of infertility in the bitch (Johnston, 1980; Lein, 1983). These infections are thought to be subclinical in the infertile bitch, only occasionally resulting in obvious vaginitis, metritis, pyometra, or systemic infection. It has been recommended that the anterior vagina of infertile bitches be cultured with a guarded swab (Accu-CulShure, from Accu-Med, Pleasantville, NY; Guarded Culture Instrument, from Kalayjian Industries, Long Beach, CA; and Tiegland Swab, HL 206400, from Haver-Lockhart Laboratories, Shawnee Mission, KS). Bacterial isolation and identification, as well as antimicrobial sensitivity, are suggested, after which the bitch can be given the appropriate antibiotics for 4 weeks (Johnston, 1980). However, it is difficult to establish the role of bacterial infections in canine infertility. Virtually all normal bitches have bacterial flora in the anterior vagina, and similar types of aerobic bacteria are present in the vaginal vaults of infertile bitches (Olson et al, 1983; Okkens et al, 1992). For these reasons, a request by stud owners that a vaginal culture be free of bacteria prior to mating is nonsensical (Watts et al, 1996; Wright and Watts, 1998).
Approximately 95% to 100% of normal bitches harbor aerobic bacteria in the vaginal tract (see Table 23-2; Bjurstrom and Linde-Forsberg, 1992a). A wide variety of bacteria have been isolated from normal canine vaginal tracts, and the numbers are often increased during proestrus and estrus. Merely isolating bacteria from the vagina does not constitute the basis for a diagnosis of disease; rather, it is likely to confirm that a bitch is normal. Furthermore, the most worrisome organism, B. canis, may be difficult to isolate. A negative culture result, therefore, does not ensure that a bitch is free of an infectious disease.
The types of bacteria may vary with the age of the bitch; a higher percentage of prepubertal bitches have coagulase-positive staphylococci than do postpubertal dogs. The stage of the cycle did not alter the types of bacteria isolated in some studies, but other studies demonstrated increased numbers in proestrus and estrus (Allen and Dagnall, 1982; Baba et al, 1983). In a more recent study, the bacteria isolated did vary with the stage of the ovarian cycle (Fig. 24-3) (Bjurstrom and Linde-Forsberg, 1992a). The composition of the gram-positive and gram-negative organisms has been found to be unique to individual dogs.
FIGURE 24-3 Variation in the frequency of isolation of five bacterial species from the vaginas of 59 bitches during various stages of the estrous cycle. (), Pasteurella multocida; (), β-Hemolytic streptococci; (), Escherichia coli; (), Staphylococcus intermedius; (), Enterococci.
(Bjurstrom L, Linde-Forsberg C: Am J Vet Res 53:665, 1992.)
Normal flora usually are recovered in mixed cultures of light to moderate growth (see Table 23-2; Bjurstrom and Linde-Forsberg, 1992a). If an organism is a significant pathogen, it usually produces clinical signs, is recovered in large numbers, and is present in a nearly pure culture because it gains advantage as a pathogen and overgrows the normal mixed flora (Allen and Dagnall, 1982; Allen, 1986; Olson et al, 1986). Of 826 vaginal swabs taken from 59 healthy, fertile bitches, cultures of only one organism were identified in 18%; mixed cultures were seen in 77%; and completely negative results occurred in only 5% (Fig. 24-4) (Bjurstrom and Linde-Forsberg, 1992a).
(Bjurstrom L, Linde-Forsberg C: Am J Vet Res 53:665, 1992.)
Some owners of stud dogs require a “negative” vaginal culture from the bitch to be used in breeding. However, most male dogs harbor microorganisms in the prepuce and urethra similar to those identified as normal vaginal flora (Bjurstrom and Linde-Forsberg, 1992b). There is no justification for refusing to breed a bitch to a stud dog because bacteria have been isolated from the vagina.
It should now be clear that it is unjustified to associate positive findings on vaginal cultures with infertility. Systemic antibiotics may have significant side effects. Heavy growth of one bacteria is more likely to be normal than abnormal. Treatment with vaginal douches for 2 to 3 weeks, with or without systemic antibiotics, may be beneficial, but such therapies should be reserved for bitches with obvious clinical signs of infection, such as a purulent vaginal discharge (Bjurstrom and Linde-Forsberg, 1992a and 1992b).
Finally, the canine uterus may contain small numbers of bacteria and still be normal (Baba et al, 1983). Obtaining a uterine culture requires laparotomy or transcervical uterine cannulation during proestrus, estrus, or diestrus. However, in normal fertile bitches these phases of the estrous cycle are associated with migration of bacteria from the vaginal vault into the uterus via the relaxed cervix (Watts and Wright, 1995). Without obvious vaginitis or pyometra, vaginal cultures are not believed to be of benefit in managing the infertile bitch.
Mycoplasma and Ureaplasma are organisms commonly cultured from the vaginal tract of normal bitches. However, a syndrome of poor conception, early embryonic death, embryonal or fetal resorption, abortion, stillborn pups, weak newborns, and neonatal death has been suggested to be caused by these smallest of free-living microorganisms. Currently, evidence regarding the pathogenesis of these disorders is circumstantial (Doig et al, 1981; Lein, 1989). As with bacterial culture results, if large numbers of these organisms are identified in pure or nearly pure growth from the vaginal vault of a breeding bitch with an infertility problem, these microorganisms may be at fault. However, in one study 59% of healthy, fertile bitches had Mycoplasma organisms recovered from vaginal swabs (Bjurstrom and Linde-Forsberg, 1992a). Management includes isolation of the animal and tetracycline or chloramphenicol therapy for 10 to 14 days (Lein, 1986).
The bitch with chronic endometrial disease is likely to be infertile. These dogs could experience normal ovarian cycles, ovulate, and have fertilized eggs but fail to support pregnancy because of the abnormal uterine environment that prevents implantation or that would result in fetal resorption (Allen and Dagnall, 1982). After evaluating the male and the owner’s management practices, the clinician should be able to assess the likelihood of an ovarian problem. If the male is normal, ovarian function is normal, the bitch is free of brucellosis, and the timing of breeding is correct, an underlying endometrial problem is possible. CEH (sterile or infected) can be extremely difficult to confirm. The diagnosis is suspected if the nonpregnant uterus is thickened or abnormally large in anestrus or diestrus. Although a thickened uterine wall is a potentially palpable abnormality, it is difficult to be certain that one is palpating the uterus. Radiographically, the nonpregnant uterus is rarely visible. If the uterus is visible in a bitch with an infertility problem, endometrial disease is possible. Similarly, visualization of the nonpregnant uterus using abdominal ultrasonography may be a means of documenting the presence of a thickened endometrium or of intraluminal fluid. The diagnosis can be confirmed only by uterine biopsy.
Procedures for transcervical cannulation of the uterus are now feasible with injection and aspiration of sterile fluid for culture and cytology (see Chapter 20). Cells identified in normal aspirates include endometrial cells, leukocytes, erythrocytes, cervical cells, bacteria, and sperm. Endometrial cells appear degenerative in diestrus and anestrus. Neutrophils are the most common white cells present during proestrus and estrus (Watts et al, 1997 and 1998). This procedure can aid in the recognition of CEH and other endometrial disease.
Early fetal resorption usually appears to both owner and veterinarian as primary infertility because early pregnancy is so difficult to confirm. Pregnancy can-not be recognized by palpation until after 21 days of gestation, and then the diagnosis is subjective. Radiographically, pregnancy cannot be confirmed until 42 to 45 days of gestation. The earliest that pregnancy can confidently be identified is approximately 16 days after first breeding, using ultrasonography. This imaging technique has been help-ful in the detection of early fetal resorption. Early fetal resorption suggests an endometrial disorder (infection or CEH), failure of corpora lutea to support pregnancy (hypoluteoidism), infectious disease (e.g., brucellosis), fetal defects (e.g., chromosomal anomalies), or some less common disorder. However, early embryonic loss has not been well investigated, and in most cases the diagnosis is speculative. Only definitive diagnosis of pregnancy through ultrasonography with demonstration of fetal death and resorption is specific for recognition of this condition. With such a diagnosis, the management alternatives are to use a different male on the next cycle or to consider uterine culture and biopsy by means of surgery or transcervical cannulation (Wright and Watts, 1998).
Plasma progesterone concentrations begin to rise prior to the onset of standing heat and decline to basal levels immediately prior to parturition. The first 6 to 7 weeks of diestrus are usually associated with progesterone concentrations of 5 to 50 ng/ml. With any bitch diagnosed as having an infertility problem, the plasma progesterone concentration should be evaluated 10 to 20 days after termination of standing heat and once or twice weekly thereafter. These studies should be completed in conjunction with evaluation by abdominal ultrasonography.
If the progesterone concentration is below 1.0 ng/ml when a bitch is timed to be in diestrus, either she never ovulated or the corpora lutea have failed to synthesize and/or secrete progesterone. Serum progesterone concentrations above 5 ng/ml should be sufficient to maintain pregnancy. If the progesterone concentration is 1.0 to 5.0 ng/ml, the amount of progesterone secreted may be insufficient to maintain pregnancy (hypoluteoidism), and abortion or fetal resorption may result. If fetuses are observed on abdominal ultrasonography early in gestation, abortion or fetal resorption should become demonstrable with repeated ultrasound examinations. (See Chapter 21 for a complete discussion of hypoluteoidism.)
To complicate matters, decreased progesterone concentrations in diestrus are not always a primary problem. Fetal factors, placentitis, or exogenous glucocorticoid therapy are a few of the many potential causes of premature luteal regression. In some situations progesterone administration may be contraindicated, but these conditions are not completely understood. Progesterone therapy should be recommended only with great caution.