Pyometra, where the uterus becomes engorged with pus, is a common disease of breeding queens.
Pyometra appears to be triggered by hormonal changes post-coitus, when failure to conceive results in excessive progesterone levels, resulting in cystic endometrial hyperplasia and sloughing of cells lining the uterus. The resultant endometrial debris invariably becomes necrotic and secondary bacterial infection occurs, usually from vaginal flora which have entered the uterus via the semi-dilated cervix (post-oestrus). Pyometra usually begins as endometrial hyperplasia that progresses into a severe endometrial infection with an accumulation of purulent exudate in the uterus.
Pyometra occurs in queens, usually over 4 years of age, and there is usually a history of recurrent oestrus with failure to conceive. Early signs of 'open' pyometra include vaginal discharge (which may vary from port-wine colored, to mucoid, to frank yellow pus). There may be hyper-vigilant grooming of the perineal area associated with the vaginal discharge. Abdominal distension is common, and polyuria/polydipsia is not as common as it is in dogs. In early cases, queens are usually bright and alert, but endotoxaemia is common, leading to bacterial sepsis, with lethargy, anorexia, vomiting and DIC common sequela to early signs. Sudden deaths are not uncommon is this disease, where queens can be vigorously playing, then suddenly die from toxic shock associated with spontaneous traumatic rupture of the engorged uterine horns.
Most queens present with abdominal distention, vaginal discharge, and a firm tubular structure palpable in the mid-abdomen. Serum biochemical abnormalities included hyperkalemia, hyponatremia, and azotemia.
Queens with a closed cervix pyometra have abdominal enlargement with no vaginal discharge and may be severely ill with septicemia. They can be more challenging to diagnose and often requires careful historical assessment of the queen to confirm a suspicion of this disease. Further tests, such as radiography, full blood analysis and ultrasound may help in diagnosing this disease, but a high index of suspicion is usually made from history and presenting signs. Blood analysis commonly reveals a marked neutrophilic leucocytosis with a regenerative left shift. Some have a mild anaemia.
Delay in diagnosis can be life-threating, due to the development of DIC which, in spite of aggressive therapy, including ovariohysterectomy, often leads to septic shock and seizures. Bouts of ictus may continue for 12-24 hrs. Recovery from seizures requires prolonged stabilization with relaxant drugs such as benzodiazepines.
Initial management of queens with pyometra revolves around patient stabilization.
- Regardless of the form of therapy chosen, many cats are septic and azotemic. IV fluids recommended are Hartmanns solution supplemented with 20 mmol potassium chloride (KCl)
- Antibiotic therapy should be started with a broad-spectrum product such as enrofloxacin (Baytril®-Bayer; 5 mg/kg, PO, once daily) or amoxicillin/clavulanate. Choice of antibiotic may also be based on results of culture and sensitivity testing of vaginal discharge. However, antibiotic treatment as sole therapy is not usually successful in preservation of fertility.
- Ovariohysterectomy is the treatment of choice for queens not valuable to a breeding program, and is the only choice for those queens with closed cervix pyometra or critically ill queens.
- Valuable breedings queens with open cervix pyometra may be treated with prostaglandin F2α (Lutalyse®-Pharmacia & Upjohn) and antibiotics. Prostaglandin treatment causes evacuation of the uterus via smooth muscle contraction. Patients suitable for prostaglandin treatment are young queens that are not seriously ill and have no evidence of retained fetal tissue or viable fetuses on abdominal ultrasound. Protocols in the literature include doses ranging from 0.1 to 0.25 mg/kg Lutalyse® subcutaneously once or twice daily for up to 5 days. A simlarly succesful protocl has been reported using cloprostenol (5 μg/kg body weight SC) on three consecutive days and amoxicillin (20 mg/kg body weight IM) on seven consecutive days.
Serious risks associated with prostaglandin therapy in cats are uncommon, although vomiting, diarrhea and vocalization are common for 30 minutes post-injection.
- Newer drugs showing potential as adjunctive treatment in feline pyometra include Aglepristone and cabergoline. Aglepristone (Alizin) is an antiprogestin that may be useful for reducing serum progesterone levels via lysis of corpora lutea on the ovary. Cabergoline (Dostinex®), a dopaminergic agonist, may also be useful for lysing corpora lutea by reducing levels of prolactin, a known luteotrophic factor. Neither aglepristone nor cabergoline are available for small animal use in the United States at this time.
Results of a complete blood cell count should be normal by two weeks after treatment. A clear vaginal discharge may be present for up to 10 days after treatment and is a good prognostic sign. A second series of prostaglandin injections can be given to queens that still have mucopurulent vaginal discharge at the two-week point. Treated queens should be bred on the next estrus. Antibiotic therapy may be continued until the queen is at least part way through any resulting pregnancy. Most queens are able to conceive and deliver litters after prostaglandin therapy, however pyometra is likely to recur in up to 15% of treated queens.
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- Dr Jim Euclid pers comm
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