Uterus - Inflammatory Pathology

INFLAMMATION Inflammation of the uterus may be infective or non-infective and in either case is influenced by hormonal factors.

Endometritis = Inflammation of the endometrium

Metritis = Inflammation of the whole uterine wall

Placentitis = Inflammation of the foetal attachment point of the uterine wall

Endometrosis = Chronic endometritis (mare)

Pyometra = Accumulation of pus in the uterine lumen

INFECTIVE INFLAMMATION OF THE UTERUS

Main routes of infection

Via the cervix at oestrus or parturition.
Haematogenous, mainly in the pregnant uterus.

Defence mechanisms

Closed cervix except at oestrus and post-partum.
Mucous secretions.
Leucocytosis of oestrus.
Oestrogen levels at oestrus render the uterus unsuitable for the growth of certain organisms.

Infection at mating

First mating may lead to mild non-specific endometritis and infection is usually rapidly cleared by neutrophils.
Infected semen via AI or natural infection can lead to apparent decreased fertility or abortion/stillbirth.

Post-partum

Infection of the non-pregnant uterus is usually via the vagina after parturition or abortion, there is increased risk if retained placenta, dystocia or failure of involution (in the bitch).

Cow: A. pyogenes, Fusiformis, S. aureus, E. coli
Sheep: Clostridia.
Bitch/queen: E. coli, Staphylococcus, Streptococcus.
Mare: Strep. zooepidemicus, E. coli, Pseudomonas, Klebsiella (may also occur as a result of chronic endometritis unrelated to parturition).

Gross lesions
Foul smelling dark red/yellow uterine contents with placental debris and ulcerated and congested haemorrhagic mucosa. Fibrin tags present on serosal surface.

Sequelae

Septicaemia - fever, depression
Embolic spread - endocarditis, renal infarcts
Ascending infection - salpingitis
Descending infection - cystitis and pyelonephritis
Chronic endometritis
Pyometra - cow may be associated with persistent CL, i.e. uterus is susceptible to infection but the cervix is closed.

(Pyometra may also occur as a result of mechanical obstruction of the cervix, e.g. by scar tissue as a result of prolonged endometritis or dystocia. In dog and cat pyometra is usually associated with cystic hyperplasia of the endometrium ).

Information by permission of Professor RW Else