Pyometra is a common disease of intact female dogs and carries with it a concern for mortality as a result of disease. According to one study in colony beagles, almost of female dogs will develop pyometra by 10 years of age.1 In some countries, this disease is primarily managed aggressively by ovariohysterectomy, while other countries choose a medical approach to therapy.
Indications for Medical Treatment
Given the recent interest in the impact of gonadectomy on both male and female dogs relating to a variety of non-neoplastic and neoplastic conditions, many veterinarians have shifted their original views of gonadectomy as being an “easy” choice relating to general health and well-being of the animal involved.2 While the necessity of surgery can be easy to argue against in the male dog for prostate disease, the recurrence of pyometra on subsequent cycles in bitches makes long-term management of this condition a poor choice for a large number of cases. Although the presence of estrogen may have a favorable impact for some conditions for that individual relating to cancer, orthopedic, autoimmune, and behavioral conditions, the potential health risk of recurrent pyometra relating to these hormones at each subsequent cycle is a serious concern. Severity of condition at presentation may limit medical management despite owner’s intentions to preserve the uterus for breeding or show, or other suspected health benefits.
A clinician may advise medical therapy because of certain risk factors for this dog. If the dog has a known significant surgical risk, such as a heart condition, it may be preferred to medically manage a pyometra, and after resolution elect to promote an anestrus state via GnRH injections or implants, or treatment with other cyclic suppressing options. Additionally, medical therapy may provide an option for temporary management if surgery is preferred but cannot be pursued immediately due to the animal’s medical condition. The expense is generally much higher with medical treatment options versus surgical options. If the owner would like to pursue ovariohysterectomy to resolve the condition, this is the best option for permanent resolution and in many cases best prognosis. Ovariohysterectomy is curative of the condition2, though prognosis may vary depending on secondary disease processes.
In some medically managed cases, ovariohysterectomy may be required for resolution, and this should be an endpoint all owners should be prepared for.
If the intention is to keep the dog intact for showing or breeding purposes, medical management of the cycle may be an option, if breeding follows on the next cycle. In regard to owner’s intention, the value of the animal to stay intact is often considered, since the potential [sic].
Clinical presentation of pyometra may range widely. Often dogs will present with lethargy, inappetence, and fever, with or without the presence of purulent, foul-smelling vulvar discharge. The uterus may be palpably enlarged on palpation; however, manipulation should be gentle given the potential for rupture of the uterus. Cytology and culture of the fluid, if present, can provide further diagnostic evidence. Cytology generally reveals highly cellular fields of degenerative neutrophils with proteinaceous material covering much of the slide. Intracellular organisms may be noted. Escherichia coli is the most commonly isolated organism in canine pyometra.3 Radiographic images can suggest pyometra, but the best option for sensitive diagnosis of a fluid filled uterus is ultrasound. Ultrasound should reveal a hyperechoic swirling fluid within a distended uterus. Diameter of the uterus can vary widely based on animal size and severity of condition.
Ovariohysterectomy is generally offered as a primary recommendation for pyometra management. Ovariohysterectomy is considered curative.2 For medical treatment, the patient generally will require hospitalization and monitoring, intravenous antibiotics, toxicodynamic drugs (prostaglandins), and luteolytic drugs.4 In some countries, drugs with antiprogesterone effect are an excellent complement for treatment. Many of the drugs involved in medical pyometra management will result in an inappetant patient, who may have other gastrointestinal side effects such as vomiting and diarrhea. In open pyometra cases, immediate evacuation of fluid from the uterus should be observed following toxicodynamic drug administration. Fluid replacement and maintenance may be required.
As a compliment to treatment, serial blood panels should be observed for improvements. Complete blood count and chemistry panel may be normal at presentation for some pyometras, but continued assessment is still important if electing to manage medically. Ultrasound should be utilized to monitor progressive evacuation of the uterus daily. If fluid volume is not reducing over time, surgical intervention and ovariohysterectomy may be more effective for this patient.
For closed pyometras, medical management can be more challenging. Prostaglandin E can be used to encourage relaxation of the cervix, via intravaginal deposit. Milder treatment with toxicodynamic drugs is required, as uterine rupture is at higher risk. Once discharge is noted from the vulva, the protocol can be adjusted to mirror the open pyometra patient.
A novel approach using endoscopic-guided lavage of the uterus to remove pathogenic material more aggressively is being attempted in some practices, however, study of effectiveness or risk for uterine rupture is yet to be established.
Mortality rates for pyometra are reported as 0% and 17% in dogs, and 8% in cats.5 Prognosis varies widely and is significant affected by severity of clinical presentation. In general, closed pyometra carries a lower prognosis for successful medical management, though both closed and open pyometras may be managed successfully through proper treatment. Any animals with kidney enzyme derangements are poor medical management candidates.
Prognosis for fertility for future breeding is fair for bitches that are relatively young when affected. Pyometra in most cases shares a close association with cystic endometrial hyperplasia, which itself can be a cause for infertility. Fertility will in most cases be negatively impacted by the presence of pathogenic fluid, but often these bitches can be bred back successfully if proper management is pursued.
Following treatment, it is important that the animal be bred on the cycle immediately following treatment, otherwise pyometra may occur again. As soon as the animal’s reproductive needs are fulfilled, it is advised to ovariohysterectomized these animals given their risk for recurrent pyometra manifestation.
Pyometra is a common disease of bitches worldwide. The disease in many cases can be managed medically, as an alternative to surgical intervention and ovario-hysterectomy. While surgical treatment should be a primary option for treatment for most patients, medical management may provide an alternative approach to resolve the clinical signs to allow the animal to remain intact, at least temporarily.
1. Fukuda S. Incidence of pyometra in colony-raised Beagle dogs. Exp Anim. 2001;50:325–329.
2. Root MV. Determining the optimal age for gonadectomy of dogs and cats. J Am Vet Med Assoc. 2007;231(11):1665–1675.
3. Krekeler N, Marenda M, Markham PF, Charles JA, Wright PJ. The role of strain-specific adhesin genes in binding of pyometra-inducing E. coli to canine endometrium. ACT/SFT Conference Abstract Presentation. 2011.
4. Fieni F, Topie E, Gogny A. Medical treatment for pyometra in dogs. Reprod in Dom Anim. 2014;49(2):28–32
5. Johnston SD, Root MV, Olson PNS. Canine and Feline Theriogenology. Philadelphia: W.B. Saunders Company; 2001