Early endometritis in female dogs generally manifests as a slight increase in the size of the uterus, such as the thickness of a finger. If it is a large dog, the larger the uterus, the thicker the endometrium, and the smaller the uterine cavity. Animal B-ultrasound examination images show: the cross-section of the uterus is "ring-like", the uterine wall is displayed as a ring-shaped light band, and the inside of the ring is the image of the uterine cavity. Animal B-ultrasound images vary with the contents of the uterus, showing weak echo dark areas or strong echo light spots and light groups; in animal B-ultrasound images, the longitudinal section of the uterus is a three-layer sandwich structure, the upper and lower weak echo light bands are the images of the uterine wall, and the middle strong echo light band is the image of the uterine cavity. Some uterine longitudinal sections are three-layer sandwich structures, the upper and lower uterine walls are displayed as strong echo light bands, and the uterine cavity is displayed as a weak echo dark area.

As endometritis progresses, the uterus becomes larger and larger, with a sense of fluctuation when touched, and more and more fluid or pus accumulates in the uterine cavity. On the contrary, the uterine wall will be thinner than in the early stage of endometritis. The animal B-ultrasound probe performs a longitudinal tomographic scan on the abdomen. The longitudinal scan shows a long, wide-diameter, echo-free, uniform, liquid dark area, separated by obvious walls above and below. The adjacent deep area is shown as a circular liquid dark area, surrounded by obvious walls. When closed uterine pyometra occurs, it can be seen that the uterus on both sides becomes uneven in thickness, forming more than two cystic masses with thin and smooth walls and clear boundaries. The contents appear as echo-free areas. However, due to the different nature of the contents, the echograms on animal B-ultrasound are very different. If the contents have many cellular components, scattered clumps or scattered strong echoes can be seen.