Pyometra in dogs: clinical signs, causes, diagnosis and treatment
It is a secondary, non-contagious infection caused by a combination of several factors: the rise in progesterone following oestrus, certain morphological changes in the endometrium and an opportunistic bacterial infection. Pyometra must be treated urgently, as its prognosis will depend on the speed and effectiveness of the therapy administered.
Clinical signs of pyometra in dogs
Pyometra in dogs usually appears in females older than 5 years, although it may appear after their first heat cycle. It develops in the metestrus phase, that is, in the weeks after oestrus when the female has higher progesterone levels.
In 85% of cases, dogs with pyometra will have bloody or purulent vaginal secretions at some time during the second to eighth week after oestrus. This is called open pyometra if the cervix remains open. However, there is also closed pyometra, in which case there is no vaginal discharge and the prognosis is more serious.
The clinical signs of pyometra in dogs include fever, lethargy, poor appetite, polyuria and polydipsia. On rare occasions it can also course with diarrhoea and a swollen abdomen. Septicaemia, toxaemia, peritonitis and renal failure can be observed in very advanced cases or which have not received correct veterinary treatment.
Causes of pyometra in dogs
The causes of pyometra in dogs are related to the hormonal cycle. Progesterone concentrations increase after the oestrus phase, which reduces uterine contractions and promotes certain changes in the endometrium. This, in turn, encourages bacterial growth. The appearance of nodules also increases the severity of the process.
Pyometra in dogs may develop in one of two ways:
- Open pyometra: the cervix remains open, which means the uterine secretions can drain away. Open pyometra is the more benign and accounts for approximately 85% of cases.
- Closed pyometra: nodules develop in the endometrium and block the cervix, so secretions cannot drain away but instead accumulate, resulting in inflammation of the uterus. This is an acute situation that rapidly develops into a serious condition.
Diagnosis of pyometra in dogs
Pyometra can be diagnosed through the anamnesis and a physical examination, then it should be confirmed by ultrasound. If this proves inconclusive, or tumour masses in the uterus are suspected of mimicking the signs of pyometra, laboratory tests and cytology may help determine a definitive diagnosis.
Positive lab results for pyometra will reveal signs of infection and the Pap smear will return a high neutrophil count.
Treatment for pyometra in dogs
Surgery is the treatment of choice for pyometra in dogs. However, two different approaches are possible depending on the progression of the disease and the desired level of conservative treatment:
- Ovariohysterectomy. Surgical removal of the uterus and ovaries is the safest therapeutic solution and treatment of choice in most cases. Support treatment should also be considered, depending on the animal’s condition, such as fluid therapy, antibiotic therapy and pain relief.
- Medical treatment, including uterine lavage, transcervical drainage, antibiotic therapy and prostaglandin administration to increase uterine contractility. This treatment is suitable for mild cases and when the owner wishes to preserve the animal’s fertility, although it is important to remember that there is no guarantee the patient will still be able to bear offspring. This option is only indicated for cases of open pyometra and after assessing the patient carefully. It is contraindicated if the animal has toxaemia.
Monitor for signs of infection in the postoperative period, as advanced pyometra can lead to peritonitis.
The best prevention is sterilisation
Pyometra appears more frequently in female dogs aged over 5 years and those which have received hormone therapy with oestrogens or progestogens. Notwithstanding, all sexually mature females are susceptible to pyometra. So the best form of prevention is early sterilisation.
