Endometritis is a low-grade bacterial infection of the uterus that occurs as a sequel to a postpartum infection of the uterus, and occasionally as a result of vaginitis that ascends to the uterus. Endometritis is a significant cause of female infertility. Unlike pyometra, the infection is limited to the lining of the uterus. Little pus is produced, but the endometrium becomes inflamed and harbors bacteria. This creates an unfavorable environment for fertilization and the implantation of embryos.

A bitch with endometritis appears to be in good health, has a normal heat period, and mates successfully, yet fails to become pregnant or is found to be pregnant but does not deliver puppies. The diagnosis should be considered whenever a bitch is bred at the right time but fails to conceive on two or more heat cycles.

Endometritis is difficult to diagnose. Abdominal palpation or ultrasonography during diestrus or anestrus may reveal a uterus that is somewhat larger or thicker than normal. Uterine biopsy confirms the diagnosis, but requires laparoscopic abdominal surgery.

Treatment: There is no effective treatment for endometritis. Hysterectomy is recommended for bitches who are not intended for breeding. This eliminates the risk of pyometra.

If future breeding is desired, consider using oral antibiotics and/or topical antibiotics infused into the uterus. Antibiotics are selected based on cultures taken from the cervix. There may be benefit in starting an antibiotic seven days before breeding and continuing it until the bitch develops the behavioral signs of heat.