Endometritis in dairy cows is an inflammation of the endometrium that commonly occurs in dairy cows after delivery. According to the degree of mucosal damage and the nature of the secretions, it can be divided into latent, chronic catarrhal, chronic catarrhal suppurative and chronic suppurative endometritis.

The impact of endometritis on reproduction varies according to the degree of inflammation, the time required for recovery of endometrial damage, damage to endometrial glands, and changes in the oviduct environment. Endometritis prolongs the calving interval, reduces milk production, increases the culling rate, increases treatment costs, and wastes milk during antibiotic treatment, causing great economic losses.

Uterine abnormalities that can be diagnosed by B-ultrasound in cattle include endometritis, uterine suppuration, embryo loss, and fetal mummification. When a dairy cow suffers from endometritis, the uterus contains inflammatory exudates, which are generally in a free-moving state. The area where it is located does not produce echoes or echo attenuation, and the outline of the uterine cavity is unclear.

The uterine cavity is expanded, and the cavity contains fractions of small fragmented semi-reflective structures to varying degrees. The degree of reflection depends on the composition of the fluid in the uterus. When the uterine contents are thick and filled with white blood cells and fibrous fragments, their reflective properties are similar to those of the uterine wall. For embryo loss, the uterine wall thickens, and the fetal bones are stretched in the non-reflective fetal fluid, which can produce reflections. During fetal cadaverization, the fetus is in a mass and completely lacks fetal fluid.

When using B-ultrasound to examine infertile cows, it was found that the uterine wall of cows with endometritis had clear contours, irregular inner edges, and thickened uterine walls. Using ultrasound to detect the fetal heartbeat can predict the life or death of the fetus in the cow's uterus. The fetal sac is filled with liquid dark areas, the embryo cannot be seen, the echo in the uterus is disordered, and the fetal sac, placenta and fetal structure cannot be distinguished, which all indicate embryonic death.