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 11 Korea Jin-do dogs. Serial ultrasonographic examination was done daily during the first week, 3 days interval from 8 to 30 days, and weekly from 31 to 100 days postpartum, respectively.
Of 11 postpartum bitches, 10 bitches (90.9%) had normal involution and 1 bitch (9.1%) had subinvolution of the placental sites (SIPS) by gross findings, vaginal discharges, and by ultrasographic findings, uterine shape and echogenicity.
The excretory period of vaginal discharges in 10 normal bitches of uterine involution was finished completely at 20.2±4.6 days (Mean±SD) postpartum, but in 1 SIPS at 50 days postpartum.
The short axis shape of the uterus was initially often flaccid-appearing. It varied from circular to crescent shaped to polygonal. This lasted until 16.5±3.7 days postpartum, during which time the short axis uterine shape gradually changed to circular. Also, the long axis shape of the uterus was created a beaded appearance of the horns until 29.9±3.2 days postpartum. After 30 days, it was appeared as tubular shape without distinguished between placental and interplacental sites.
The ultrasonographic image of the postpartum uterus consisted of four echogenicity distinct layers. Uterine wall was represented the very hyperechoic serosa, hypoechoic myometrium, hyper echoic endometrium and anechoic structures of fluid in the uterine cavity until 7 days postpartum.
The individual uterine layers were most prominent during the first week postpartum, and they became progressively less distinct throughout the course of uterine involution. Anechoic structures of fluid in the uterine cavity was detected until 25.0±6.4 days postpartum, after which time it was not reliably detected.
The uterine diameter was decreased not only in the placental sites frorm 24.1±2.5㎜ at 1 day to 15.4±1.4㎜ at 7 days postpartum, but also in the interplacental sites 14.9±1.5㎜ at 1 day, 10.6±0.8㎜ at 7 days postpartum. There wss a general trend of decreasing uterine diameter, which occurred more rapidly at the placental sites. At 31 days pastpartum, these diameter reached almost same size, after that time, they could be not distinguished between placental and interplacental sites. At 87 days postpartum, the uterine diameter was 5.6±0.6㎜ both placental and interplacental sites, and the uterine horns were uniform hypoechoic, tubular structures without enlargement. Therefore, complete involution of the uterus occurred at that time.
It was concluded that normal postpartum uterine involution in Korea Jin-do bitches appeared to be completed around 87 days postpartum by gross findings such as vaginal discharges, and by ultrasonographic findings, uterine shape and echogenicity. Also ultrasonographic characteristics of the postpartum uterine involution were described. Therefore, these result suggest that ultrasonographic assessment is a reliable method for diagnosing the SIPS and uterine dysfunction, such as pyometra in bitch.
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