When the mare is in heat a radioactive substance can be infused into her uterus and the amount of radioactivity that remains in the uterus after two hours can be measured. If she has a delay in her ability to clear the uterus, she will clear virtually nothing. The veterinarian can ultrasound the mare's uterus 24 hours after she has been bred to determine if she is retaining fluid. If there is fluid, treatment should be performed at that time. However, the mare may not conceive because the inflammation has been present for too long.
Treatment is aimed at making the uterus contract so that the mare pushes the fluids out.
This can be accomplished with drugs such as oxytocin and prostaglandins. Prior to injection of the drug, the veterinarian may want to lavage the uterus with fluids to remove the pus. The longer pus remains in the uterus, the more inflammation it causes and the longer it may take the uterus to heal. The veterinarian waits four hours so that the sperm have time to reach the oviduct. A second examination with ultrasound is conducted 24 hours after breeding to determine if there is any fluid left in the uterus.