Ovarian remnant syndrome

Ovarian remnant syndrome (ORS) is the presence of functional ovarian tissue in a previously ovariohysterectomized bitch or queen. Reported causes are surgeon error and presence of ectopic or accessory ovarian tissue that becomes functional after removal of the main ovary; presence of such tissue has been reported in humans, cows, and cats and is considered very rare in domestic animals. Diagnostic techniques include vaginal cytology, hormone assays, and imaging techniques. Vaginal cytology is best used when the owner perceives the bitch or queen to be in estrus. Hormones assayed include estrogen, progesterone, luteinizing hormone, and anti-Mullerian hormone. Ultrasonography of the abdomen is described for diagnosis of ORS. ORS can be left untreated, or can be treated medically or surgically. Surgical repair is the treatment of choice. Medical treatment consists of estrus suppression for the life of the animal. All ovarian tissue removed should be submitted for histopathology.