Ultrasonographic Evaluation of Uterine Stump Size in Ovariohysterectomized Dogs Receiving Estriol Compared to Control Dogs

In ovariohysterectomized dogs, the uterine stump rarely causes clinical disease. However, changes could occur in this anatomic structure due to exposure to estrogen therapy. Ultrasonographic examination of the uterine stump has not been reported in dogs receiving estriol and normal dimensions for this area have not been reported for ovariohysterectomized dogs. Therefore, the aims of this study were to retrospectively evaluate records and ultrasound images from dogs receiving and not receiving (controls) estriol as well as defining a standard method to measure the uterine stump. Clinical features of dogs administered estriol were also reported. Fourteen dogs receiving estriol and 14 control dogs were included in the study. Seven dogs receiving estriol had changes associated with the external vulva, 5 were noted to be "hooded" and 3 were "prominent/swollen." Ultrasonographic transverse maximum uterine stump measurements were available for 4 dogs receiving estriol (median 0.81 cm, range 0.53-1.4). The maximum uterine height/aorta ratio was available for only 2 dogs receiving estriol (0.9 and 0.6). The median transverse maximum height of the uterine stump noted in the control group was 0.43 cm (range 0.28-0.52 cm); The maximal uterine height/aorta ratio was a median of 0.48 in the control group (range 0.32-1.1). Normal values for the uterine stump measurements can be standardized to the distal aorta for consistency. Vulvar enlargement was the most common physical examination change in our dogs receiving estriol. Routine screening, including ultrasonography is not usually indicated for dogs receiving estriol, but can be tailored to the individual patient.