This study was carried out the normal serial ultrasonographic appearance of the postpartum uterine involution with small pet bitches. Postpartum changes in uterine shape, architecture, echogenicity and diameter were monitored with ultrasonography in small pet bitches (Miniature Schnauzer, Cocker Spaniel and Shih-tzu). In the Miniature Schnauzer bitches, uterine diameter of the placental sites and interplacental sites were decreased from at 1 day to at 7 day, and at 1 day to at 7 day postpartum. In the Cocker Spaniel, the placental sites and interplacental sites were decreased from at 1 day to at 7 day, and at 1 day to at 7 day postpartum. In the Shih-tzu, the placental sites and interplacental sites were decreased from at 1 day to at 7 day, and at 1 day to at 7 day postpartum. And uterine diameter was no statistically significant difference among bitches (p>0.05). At 67 days, the uterine diameter in Miniature Schnauzer bitches were 6~7 mm both placental and interplacental sites, and the uterine horns showed uniform hypoechoic, tubular structures without enlargement. In present study, the involution of the uterus was completed at 67 days after parturition in Miniature Schnauzer, and 65 days in Cocker Spaniel and the Shih-tzu. There were no significant differences of normal postpartum uterine involution between small pet bitches (p>0.05). In conclusion, the postpartum involution of small pet bitches appeared to be completed normally at 65~67 days after parturition and could be identified by gross findings such as vaginal discharges and ultrasonographic findings of uterine shape and echogenicity.

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.