Ultrasound: Uterus

Uterine edema and fluid are also determined by ultrasound. If the mare is not showing estrus or cannot be teased, it is very important that the uterus have edema when you breed. Edema indicates a high level of estrogen, and that the mare is really in estrus. Remember that some mares do have diestrual follicle growth and ovulation or ovulation during pregnancy so that large follicles alone may not indicate estrus.

Normal estrual uterus with edema	Normal estrual uterus with edema and fluid

The estrual uterus (outlined in blue) has intracellular fluid which makes a cross section of the uterus look like the cross section of a citrus fruit. In healthy mares with an open cervix, a small amount of fluid is not a problem.

Accumulation of fluid in the uterine lumen is normal in some mares but if the fluid is cloudy or there are large pockets of fluid, then the mare may have a uterine infection (picture on left; cloudy fluid outlined in red). If the fluid is clear, the mare may need to be managed by giving oxytocin 6 hours after breeding or have a post breeding lavage (flushing the uterus with sterile fluid) to remove the excess fluid.