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Pyometra in the bitch (Proceedings)
When pyometra occurs in a pet animal, the decision for surgical intervention is uncomplicated. When pyometra occurs in a valuable animal intended for breeding, the breeder client often opts for medical treatment.
• Review endocrinology and pathogenesis of pyometra
• Discuss diagnosis of pyometra
• List decision-making factors relevant to the choice of medical vs. surgical treatment
• Present medical treatment protocols
• Discuss prevention and recurrence of pyometra
When pyometra occurs in a pet animal, the decision for surgical intervention is uncomplicated. When pyometra occurs in a valuable animal intended for breeding, the breeder client often opts for medical treatment. Medical treatment must be aggressively managed. Careful post-treatment management of the intact bitch is required if she is to successfully conceive, establish pregnancy and carry the pregnancy to term.
• Presenting patient is an intact bitch; history of a recent estrus
• Clinical signs include a palpably enlarged uterus, ± purulent vaginal discharge, depression, lethargy, PU/PD, vomiting and abdominal distension.
• Differential diagnoses include pregnancy, severe vaginitis, diabetes mellitus and hyperadrenocorticism.
• Radiography – contraindicated in pregnancy < 42 days post breeding, large soft tissue density tubular structure imaged in caudoventral abdomen.
• Ultrasonography – intraluminal uterine contents imaged, uterine wall thickened.
• Laboratory Tests – neutrophilia usually accompanied by anemia, azotemia, hyperglobulinemia, hyperproteinemia, ↑ALT and ↑ALP, purulent cytology of vaginal discharge.
• Vaginoscopy –purulent discharge visualized emanating from the external cervical os confirms uterine origin. External os cannot be visualized with a conventional vaginal speculum.
• Culture & Sensitivity – cannot definitively diagnose pyometra but can identify the appropriate antibacterial agent to use.
Etiology and pathophysiology
• Pyometra is secondary to cystic endometrial hyperplasia (CEH).
• CEH is both hormonally mediated and progressive.
• CEH is caused by repeated exposure of the endometrium to progesterone.
• Unique to the canine, every estrus is followed by a prolonged diestral period regardless of pregnancy state.
• The vagina normally contains resident bacteria, while the uterus normally presents a sterile environment.
• Pyometra develops when bacteria invade the abnormal endometrium to the extent that purulent exudate accumulates within the uterine lumen.
• Uterine defense mechanisms "turned on" under the influence of estrogen, but "turn off" as the estrogen environment changes to a progesterone environment.
• Pregnancy may somewhat lessen the deleterious effects of progesterone.
• Pyometra can be open or closed, relative to cervical patency.
• Open cervix pyometra – purulent vulvar discharge readily apparent, systemic signs usually mild
• Closed cervix pyometra – no vulvar discharge, abdomen distended and painful, systemic sign more severe, septicemia and endotoxemia more likely
• A case of pyometra constitutes a potentially life-threatening emergency; treatment must be prompt and aggressive.
• Surgery (ovariohysterectomy) combined with appropriate antimicrobial therapy is the treatment of choice.
• Medical treatment should be reserved for valuable breeding animals that are not presented in a life-threatening state. Surgical intervention is preferable even in aged, debilitated animals.
• Medical treatment does not reverse or resolve the underlying CEH.
• The goals of medical treatment are to:
• Expel the contents from the uterus
• End the progesterone influence on the uterine environment
• Eliminate the bacteria from the uterus
• Ultimately, to restore uterine health sufficient to support a pregnancy to term.
• Successful treatment is not possible with antibacterial therapy alone; it must include hormonal therapy (in addition to appropriate supportive therapy).
• Treatment with ecbolic agents must be continued until uterine contents evacuated.
• Treatment with luteolytic agents must be continued until progesterone < 1.0 ng/ml. Recheck progesterone levels 5 to 7 days after discontinuing treatment to confirm that a rebound has not occurred.
• Prostaglandins have both luteolytic and ecbolic properties. PGF2( is the prostaglandin of choice. Cloprostenol, a prostaglandin analog, is less effective, produces more severe side effects and is not recommended for treatment of pyometra.
• Prostaglandins cause increased smooth muscle contraction which aids in expulsion of uterine contents. Adverse side effects are attributable to its action on smooth muscle in other body systems. Side effects include hypersalivation, emesis, diarrhea, abdominal discomfort, bronchoconstriction and increased blood pressure. Side effects diminish with each successive treatment.
• Prostaglandins induce abortion and can be absorbed through the skin. They should not be used on pregnant animals or handled by pregnant women.
• A number of protocols for prostaglandin therapy have been published. One recommended protocol combines a lower dosage of PGF2α with either bromocriptine or cabergoline.
• The combined protocol is reported to lessen severity of prostaglandin-induced side effects.
• PGF2αat an increasing dose of 10-25 μg/kg for 5-7 days combined with either Bromocriptine at 25 μg/kg q8-12h or Cabergoline at 5 μg/kg q24h
• Cabergoline is preferred over bromocriptine but is not available in all countries.
• If prostaglandin therapy is stopped prematurely (before luteolysis is complete), serum progesterone may rise and lead to a relapse in the patient's condition.
• Treatment with antibacterial agents must be continued until all bacteria have been eliminated from the uterus.
• TECT - (Transcervical Endoscopic Catheterization Technique)
• Surgical intervention (ovariohysterectomy) resolves pyometra and CEH permanently.
• Medical treatment resolves the pyometra but does not remove the underlying CEH; pyometra is expected to recur.
• Prevention involves avoiding progesterone influence on the uterus until such time as the bitch is ready to be breed.
• Recommend that the bitch be bred at her next estrus to a fertile stud utilizing techniques that minimize bacterial exposure to the uterus.
Patient monitoring with medical treatment
• In hospital treatment continues until the uterus is devoid of contents ultrasonographically, serum progesterone is < 1ng/ml, WBC is declining and clinical signs have disappeared.
• If, at any time during medical treatment, the patient develops septicemia or endotoxemia and her condition deteriorates, medical treatment is no longer an option. An ovariohysterectomy is performed immediately.
• A recheck at 1 week verifies that the WBC has continued to normalize, the uterus is still empty and most importantly, that the serum progesterone level has not rebounded and is still at baseline (<1 ng/ml).
Key drugs, dosages and indications
Post-treatment management of the intact bitch
• Prevent the deleterious effect of progesterone on the nonpregnant uterus.
• Plan to breed the bitch at her next estrus.
• Alternatively, prevent uterine exposure to progesterone through the administration of daily oral doses of mibolerone. Discontinue mibolerone use and breed at her next estrus.
• At proestrus, culture the bitch's cranial vagina and initiate a 3 week course of an appropriate antibiotic based upon the bacterial sensitivity findings.
• To maximize the chance for conception, inseminate the bitch at the optimal time (based on ovulation timing) with semen of good quality from a fertile male.
• To minimize the number of bacteria introduced into the bitch's reproductive tract, centrifuge the ejaculate and resuspend the sperm pellet in an antibiotic-containing extender.
• Perform an ovariohysterectomy as soon as the female's reproductive life is over.
• Maintain life-long estrus suppression for females that are poor candidates for surgery.
Pyometra is secondary to CEH. CEH is an inevitable consequence in the intact, cycling bitch. Because of her unique prolonged diestral period, pyometra occurs more commonly in the bitch and other canid species as compared to other species. Pyometra can be both prevented and cured by ovariohysterectomy. Pyometra is a hormonally induced disease and hormonal therapy is the foundation of medical treatment. Medical treatment should be considered only in cases of open cervix pyometra and only in valuable breeding animals that present in a nonlife-threatening state. Post-treatment success rate (i.e. delivering a healthy litter) is ~50%.
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