Pyometra

Chapter 139 Pyometra



M. Bronwyn Crane, DVM, DACT



KEY POINTS



• Pyometra primarily affects older, intact bitches and queens.

• The pathogenesis of pyometra is hormone dependent and often preceded by cystic endometrial hyperplasia (CEH).

• Bitches have signs of endotoxemia and may or may not have vaginal discharge.

• Diagnosis is based on a combination of clinical signs, laboratory findings, abdominal radiographs, and ultrasonography.

• The recommended treatment for bitches not intended for breeding is ovariohysterectomy.

• Depending on the severity of the condition, valuable bitches intended for breeding may be treated medically. These cases have a strong likelihood of reoccurrence.


INTRODUCTION


Cystic endometrial hyperplasia (CEH)-pyometra describes a spectrum of uterine pathology that is the most common uterine disease in middle-aged and older intact bitches and queens. It is an endocrine disease occurring during diestrus, when corpora lutea are present and serum progesterone concentrations are high. Severity of the disease varies greatly and depends on its stage of progression. CEH is mostly a subclinical disease, but bitches with pyometra may be stable with mild clinical signs or near death due to toxic shock or peritonitis. Once diagnosed, CEH-pyometra may be treated by ovariohysterectomy (OHE) or medically with prostaglandin (PG) F2α and antibiotics.



INCIDENCE


In a study of intact bitches under 10 years of age in Sweden, the 12-month incidence rate of pyometra was 2% and the average lifetime risk was 23% to 24%.1 In colony-raised Beagle bitches, the incidence of CEH was 15.2%.2 When medroxyprogesterone acetate was used for population control, the prevalence of pyometra increased in treated bitches to 45%, over a prevalence of only 5% in untreated bitches.3



PATHOGENESIS


CEH is a subclinical disease characterized by the proliferation and hypersecretion of endometrial glands, resulting in the formation of fluid-filled cysts and accumulation of glandular fluid within the uterine lumen. Alone, CEH is not associated with any signs other than infertility. CEH generally is considered the initiating stage that progresses to pyometra after uterine bacterial colonization. Pyometra is a life-threatening illness involving the accumulation of intraluminal purulent exudate within the uterus and inflammatory cell infiltration into the layers of the endometrium and myometrium. Although CEH generally precedes pyometra, the latter can occur without CEH.


CEH-pyometra typically occurs during diestrus when progesterone stimulates endometrial growth and glandular secretory activity after the uterus has been primed by estrogen. Progesterone also reduces myometrial contractility and maintains cervical closure. In addition, progesterone diminishes immune function by decreasing neutrophil chemotaxis and phagocytosis and increases endometrial bacterial adherence. Despite this, peripheral serum progesterone concentrations in bitches with pyometra are not higher than those of normal diestrual bitches.4,5 Estrogens also have a role in the pathogenesis of CEH through the up-regulation of endometrial progesterone and estrogen receptors. Administration of estrogens followed by progesterone, or progesterone alone, will induce CEH.6


Bacteria gain access to the uterus via ascension during cervical dilation that occurs with estrus. Bacteria found in healthy uteri and the uteri of bitches with pyometra are representative of the normal microflora of the vagina and cervix.7 Many bitches with pyometra also have a concurrent urinary tract infection (22% to 72%).8 The most common bacterium isolated in cases of pyometra is Escherichia coli.5 Infusion of E. coli isolates obtained from bitches with pyometra into the uteri of healthy bitches resulted in the development of pyometra.9,10 Other less common bacteria isolated from cases of pyometra include Streptococcus spp, Enterobacter spp, Proteus spp, Klebsiella spp, and Pseudomonas spp. The mechanical irritation caused by bacteria within the endometrium is a sufficient stimulus for CEH. Any stimuli, from an embryo to a piece of silk thread,11 will stimulate local proliferation of endometrial glands and hyperplastic changes within the endometrium.6,12



DIAGNOSIS


Presumptive diagnosis of CEH-pyometra is made based on the history, clinical signs, abdominal palpation of an enlarged uterus, diagnostic imaging, hematology, and biochemistry results. Differentiating CEH with mucometra from pyometra is often an important aspect of the diagnosis, because treatment recommendations may be different for valuable breeding bitches.



Signalment


The median age of dogs with CEH-pyometra in various studies is 8 to 9 years.2,14 CEH is diagnosed infrequently in dogs less than 4 years old and occurs slightly more often in maiden bitches. In a retrospective study of pyometra in cats, the mean age was 32 months.13 Although there is not an established breed predisposition for pyometra, studies examining the breed risk found an increased incidence in rough-coated Collies, Rottweilers, Cavalier King Charles Spaniels, and Golden Retrievers.1,14



History and Physical Examination


Most bitches and queens with pyometra have a history of recent estrus. The average interval from the onset of proestrus to diagnosis of CEH-pyometra is 35 days (range 20 to 70 days). In cats, most cases of pyometra occurred within 8 weeks of estrus and most of those queens were known to have been bred.13 Although pyometra is considered a disorder of diestrus, it can also occur during anestrus when progesterone is at baseline concentrations. Cases that occur during anestrus may be due to the persistence of abnormal events that occurred during diestrus or a nonovarian source of progesterone. Frequently bitches with pyometra will have a history of treatment with exogenous progestins for contraception3 or exogenous estrogens for pregnancy termination.14 Many cases concurrently have estrogen-secreting cystic follicles, ovarian neoplasia, or a history of prolonged estrus.


The clinical signs of pyometra include vaginal discharge (80%), fever (47%), polydipsia, polyuria, and vomition.15 Other signs include lethargy, anorexia, dehydration, tachycardia, tachypnea, and pale or hyperemic mucous membranes. Abdominal palpation may elicit pain or reveal a large tubular structure. Uterine exudate in the form of vaginal discharge may be purulent, mucoid, or hemorrhagic. Pyometras are further classified as open cervix or closed cervix, based on the presence of vaginal discharge. Cytology of the cranial vagina will often reveal degenerate neutrophils and bacteria. Before obtaining the cytology specimen, the cranial vagina should be swabbed using a guarded swab for culture and antibiotic sensitivity testing. A vaginal speculum examination is also warranted to rule out a vaginal abnormality or foreign body as the source of vulvar discharge. Advanced cases of pyometra may arrive in decompensatory septic shock with hypotension. Signs that are more likely to be present in cases of pyometra than in CEH include polyuria and polydipsia, lethargy, and vomiting or inappetence.16 The more severesigns associated with pyometra are due to the effects of bacterial toxins.


Clinical signs observed in queens with pyometra include vaginal discharge, anorexia, lethargy, weight loss, unkempt appearance, and polyuria and polydipsia.13 A palpably enlarged uterus is a more common physical examination finding in cats than dogs, perhaps a result of the pliability of a cat’s abdomen.

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  4. Allergic Airway Disease in Dogs and Cats and Feline Bronchopulmonary Disease

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Pyometra

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