INTRODUCTION

Pyometra is an infectious disease caused by bacteria and characterised by the presence of pus inside the uterus.

WHAT IS PYOMETRA?

Pyometra is a disease caused by infection of the uterus and accumulation of secretions and pus inside the uterus. It is very common in bitches that have reached sexual maturity. It also affects female cats, rabbits, ferrets and guinea pigs and is very rare in humans. It is a serious disease with sudden onset and life-threatening consequences if not treated in time, and can therefore be considered an emergency. Because it occurs in an organ located in the abdominal cavity, it has been compared to appendicitis, both of which involve the accumulation of pus inside a hollow organ.

CAUSES OF PYOMETRA

Pyometra is the consequence of changes in the uterus during metaestrus (the period after oestrus). It can occur at any age once fertility has been achieved, although it is more common as the animal gets older. The time of maximum risk for its occurrence is between the 6th and 8th week after the onset of oestrus. Normally during this phase the cervix that has remained open during oestrus begins to close and the endometrium returns to its normal state.

However, cystic endometrial hyperplasia can occur as an inappropriate response to the secretion of the hormone progesterone that takes place during this period, meaning that the innermost part of the endometrial wall becomes excessively thick and cysts form. In this situation, bacteria that have migrated into the uterus from the vagina find favourable conditions for their growth. In addition, progesterone decreases the contractility of the uterus and increases mucus secretion, which facilitates the closure of the cervix and hinders the drainage of the organ.

The closure of the cervix is an important factor in the severity of the disease. If the cervix remains open, the secretions produced by the infection can be expelled, which facilitates healing. This is called open pyometra. On the other hand, if the cervix remains completely closed, the pus and secretions cannot be expelled through the vulva, so they accumulate and the uterus becomes distended. This is known as closed pyometra. In these circumstances it is not uncommon for the uterus to rupture and the infection to spread into the peritoneal cavity resulting in peritonitis which can be fatal.

In ferrets this is an uncommon process that can occur in the early phase of pseudogestation, Streptococcus spp, Staphylococcus spp, E.coli, Corynebcteryum spp. depression, anorexia and fever occur and there is a risk of peritonitis due to rupture of the uterus. Ovariohysterectomy is the only therapeutic option.

In female cats it has some specific characteristics. In female cats (and rabbits), ovulation is the result of a neuroendocrine reflex that is only initiated by mechanical stimulation of the vagina, i.e. the female cat ovulates in response to stimulation of the vagina by the male. This is why the disease appears after non-fertile mating, or after exogenous administration of progesterone (contraceptives).

SYMPTOMS OF PYOMETRA

The most frequent signs and symptoms are

• Vaginal discharge which may be bloody or purulent (with pus) and is present in 85% of cases.
• Lethargy in 62%.
• Inappetence in 42%,
• polyuria and polydipsia (excessive thirst) in 28%.
• Diarrhoea, nocturia (nocturnal urination) and abdominal enlargement are less common.

If the disease progresses further, the animal may go into circulatory shock, resulting in septicaemia (presence of bacteria in the blood), toxaemia (toxins in the blood), renal failure and peritonitis.

TREATMENT OF PYOMETRA

The treatment of choice is surgical. The ovaries and uterus are removed. Antibiotic treatment and infusion of saline may be necessary beforehand to improve the animal's condition and combat dehydration.

In a small number of cases, treatment with antibiotics and prostaglandins (a substance that increases uterine contraction) can be carried out, which makes it possible to avoid surgery and maintain reproductive capacity; but this option is only applicable in selected cases in which the general situation is good and the pyometra is open.

CONCLUSION

Preventive castration avoids the appearance of uterine infections (as expected) but we must never forget that castrations must be done when the animal has its definitive size, never before the age of one year in dogs and never before 6 months in cats, rabbits and guinea pigs. This is due to the great importance of hormones in the growth and mental and physical development of the animal. It is also important to recognise the symptoms in order to be able to act quickly.