Serial ultrasonography was performed to measure the normal appearance of uterine during estrous cycle and to determine whether the unterine appearance was related to the sex hormone, progesterone and estrogen. The uterine appearances, shape, diameter and echogenicity were daily monitored with ultrasonography in 9 Miniature Schnauzer dogs undergoing II estrous cycles. During proestrus and estrous, the uterus became hypoechoic but developed hyperechoic luminal echo. In the longitudinal view, the shape of the uterus occasionally changed from rectangular to coiled or serpentine, compared to other stages of the cycle. The diameter of the uterus during proestrus and estrous was larger (range: 0.600.86 mm) than other stages (range: 0.480.62 mm) of the cycle. The rising estrogen concentrations (range: 14.5116.86 pg/ml) in plasma during proestrus correlated with changes in the uterus (p<0.05). Progesterone concentrations were 0.080.15 ng/ml at the onset of proestrus, but rose 1.061.26 ng/ml at the end of proestrus. There was no relation to progesterone concentration from onset of estrus (p>0.05). There was dramatical changes in normal uterus and sex hormone during estrous cycle. Especially, the appearance, shape and diameter of uterus were related to plasma estrogen concentration during proestrus, correlated with other stages of the cycle.

This study was undertaken to determine the normal appearance of the postpartum uterine involution. Postpartum changes in uterine shape, architecture, echogenicity and diameter were monitored with ultrasonography in 8 Miniature Schnauzer dogs. Vaginal discharge was observed visually during the 3 weeks of postpartum. A large amount of viscous dark green discharge changed progressively to a small amount of transparent discharge. In the uterine shape, the transverse images were crescent or polygonal at the beginning, but became circular after 16 days. At postpartum day 24, the longitudinal images of placental and interplacental sites were similar to each other The echogenicity of uterine structure was clearly distinguishable among the hyperechoic serous membrane, hypochoic myometrium, hyperechoic endometrium, and anechoic uterine contents during the first week postpartum, but afterward the interluminal boundaries and echogenicity became obscure gradually. In addition, the anechoic substance of the endometrial cavity was not observed after postpartum day 28. In the uterine diameter, the diameter of placental sites decreased markedly from 24 mm at the first day postpartum to 13 mm at day 7, and the diameter of interplacental sites decreased from 15 mm at postpartum day 1 to 10 mm at day 7. At postpartum day 65, the uterus (6.4 mm) changed little and had a uniform homogenous echo, and thus it was confirmed that uterine involution was completed at that time in Miniature Schnauzer dogs.