A biopsy can give you a prognosis for pregnancy and may suggest treatments that will improve the endometrial condition. A biopsy can also detect an infection more reliably than a culture or cytology. The most common type of biopsy is a simple pinch-type biopsy taken of the uterine wall in the uterine body. For detail of the endometrium at other sites within the uterus, a special speculum tool can be used that enables the veterinarian to biopsy the endometrium at several sites in the body and horns of the uterus during a single procedure. An ultrasound exam may reveal cysts in the uterus.
Cysts can also confuse the veterinarian when checking for pregnancy by ultrasound.
If there is only a small cyst or two, it is probably best to do nothing except note their location in the uterus, but if there are many large clusters of cysts it might be wise to remove them. Some mares have lost the ability to clear the uterus of extra fluid after breeding. These mares may be identified by the presence of fluids found during an ultrasound exam after breeding. There are several methods of treatment for these mares that may help improve their chances of conception. It is good practice to check any barren mare for a low thyroid level before the start of the breeding season so supplementation can be started early if needed.