Understanding Pyometra: Part II. Diagnosis, Treatment and Prognosis
March 8, 2019 (published)
Winn Feline Health Foundation

Hagman R.  Pyometra in small animals.  Vet Clin North Am Small Anim Pract 2018;48(4):639-661.

In queens with pyometra, sepsis is a complication present in approximately 86% of cases, while sepsis is identified in only 60% of affected bitches. Pyometra may be accompanied by either continuous or intermittent mucopurulent to hemorrhagic vaginal discharge (open cervix) or no discharge at all (closed cervix). A patient with a closed cervix pyometra can be much sicker systemically because there is no drainage from the septic uterus. In queens, vaginal discharge, even if present, may not be noted due to the cat’s fastidious grooming habits. The most common clinical signs of pyometra in queens are lethargy, vaginal discharge, and gastrointestinal problems such as anorexia, vomiting, and diarrhea.  Other signs displayed by cats suffering from pyometra include weight loss, dehydration, abdominal pain, abnormal mucous membrane coloration, polydipsia/polyuria, tachycardia, tachypnea, and poor grooming. Fever may or may not be present in either species.

Signalment, history, clinical signs, physical examination, hematologic and biochemical screening, abdominal radiography, and ultrasonography can all contribute to the diagnosis of pyometra.  Although affected animals may present with signs of illness post-estrus, pyometra can occur at any time during the estrus cycle. Abdominal ultrasonography is the most valuable diagnostic modality, as the distended abdomen that may occur with pyometra may be mistaken for pregnancy; moreover, it is possible for a cat to have a pregnancy in one uterine horn and pyometra or another pathologic condition such as hydrometra or mucometra in the other. Ultrasound imaging will identify intrauterine fluid as well as any pathologic changes in the uterine wall and/or ovaries. However, echogenicity of uterine fluid, while helpful in some cases, is not diagnostic of pyometra; ultrasonographic data must be coupled with other clinical findings. Patients with pyometra will be generally sicker, more lethargic, have more gastrointestinal disturbances, and have a more pronounced inflammatory response than those with mucometra or hydrometra.

Surgical treatment in the form of ovariohysterectomy, following emergency stabilization, is the safest and most effective form of therapy for animals with pyometra, especially in cases of closed cervix pyometra or pyometra with complications such as peritonitis. Surgery should not be unnecessarily delayed, as the risk of sepsis and other complications persists as long as the infected uterus remains in the animal. Ovariohysterectomy eliminates the source of infection, removes bacteria and their toxic products, and prevents recurrence.

Initial antimicrobial therapy should involve a broad-spectrum antibiotic known to be effective against E. coli, the most common pathogen in pyometra.  Bacterial culture and antimicrobial sensitivity results obtained from uterine fluid obtained after ovariohysterectomy are then used to adjust further antibiotic therapy, ideally to an agent with a narrower spectrum. Intensive postoperative care is required, but most uncomplicated cases can be discharged one to two days after surgery, with a good prognosis; mortality rates vary from 3% to 20%. Clinicopathologic parameters positively correlated with morbidity as reflected by duration of hospitalization in cats include total leukocyte counts, neutrophils, band neutrophils, monocytes, and percentage of band neutrophils, while serum albumin concentrations were negatively correlated with length of hospital stay. Queens experiencing uterine rupture associated with pyometra can have a mortality rate of 57%. Approximately 20% of pyometra patients will experience complications, most commonly peritonitis (12%).

Only carefully selected patients, generally, those with open cervix pyometra, should be treated with medical therapy only, taking into consideration the animal’s age, acute and chronic health status, and reproductive value. Animals receiving medical therapy only should also be hospitalized and monitored closely as some medications may take up to 48 hours to take effect, the medications themselves may have adverse effects, and complications or deterioration in the patient’s health status can occur, in which case ovariohysterectomy is indicated.

Many medical treatments for open cervix pyometra have been evaluated extensively in dogs, but fewer have been studied in cats. Pharmaceuticals used include agents that will prevent production or block the action of progesterone, as well as systemic antimicrobials to eliminate the infection. Other supportive care such as intravenous fluids may be needed in some cases. Medical therapy of open-cervix pyometra in cats is reported to resolve clinical illness in 95% of patients, and allow return to fertility in 60%.  The reported mean recurrence rate of pyometra in medically treated queens is 0-14%.

Drugs used for medical therapy of open cervix pyometra in queens are either natural or synthetic (cloprostenol) prostaglandin F (PGF)2α, which are luteolytic, uterotonic, and stimulators of smooth muscle contraction, and the progesterone receptor blocker aglepristone. Dosing and protocol information for queens with these agents is provided by the author; all of them have been successful in resolving signs of pyometra in queens. However, no side effects are observed with the use of aglepristone, while PGF is associated with transient side effects such as vocalization, vomiting, and diarrhea. Both natural and synthetic PGF have a narrow therapeutic index and accurate dosing calculations are crucial. Aglepristone is not licensed for use in the USA, and its use in cats is extra label anywhere. In bitches, cabergoline or bromocriptine, both dopamine agonists which have antiprolactin effects that promote luteolysis, may be used in conjunction with PGF, but no studies have been performed using these agents in a similar manner in the cat.

Stump pyometra can occur in both incompletely spayed dogs and cats, usually due to the presence of hormone-producing ovarian remnants and their effect on residual uterine tissue. Abdominal ultrasonography is a useful modality for diagnosing this condition. Exploratory surgery to remove ovarian and uterine tissue still present within the animal is required along with supportive care and antibiotic therapy. [PJS]

See also:

Hollinshead F, Krekeler N.  Pyometra in the queen:  to spay or not to spay?  J Feline Med Surg 2016;18:21-33.

Brady CA, Otto CM, et al.  Severe sepsis in cats: 29 cases (1986-1998).  J Am Vet Med Assoc 2000;217:531-535.

Nak D, Nak Y, Tuna B.  Follow-up examinations after medical treatment of pyometra in cats with the progesterone-antagonist aglepristone. J Feline Med Surg 2009;11:499-502.

Garcia Mitacek MC, Stornelli MC, et al. Cloprostenol treatment of open-cervix pyometra.  J Feline Med Surg 2014;16:177-179.