Ultrasonographic observations of the uterine regression in the ewe under different obstetrical conditions.

Involution of the ovine uterus after parturition was studied using real-time B-mode ultrasonography. The diameter of the uterus, the uterine lumen and the caruncles were investigated during the first 30 days post-parturition (p.p.) by transrectal and transabdominal application of the ultrasound probe. Ewes that spontaneously delivered showed a physiological regression of the uterus with a transversal diameter of 4.9 (+/- 0.86) cm on day 1 p.p. which decreased to 1.84 (+/- 0.14) cm until day 30. The course of uterine regression was established on these data and was described by the exponential equation: y = E + A * e(-b*t). 'E' means the final value on day 30 p.p. and 'A' the difference between the initial transversal diameter on day 1 p.p. minus the final value on day 30 p.p. The exponents 'b' and 't' indicate the downward gradient of the regression curve and also the factor time in days. Furthermore, we found that the uterine regression in ewes finishes approximately on day 17 p.p. The uterine involution was delayed in ewes after manual obstetrics and caesarean section, in addition the incidence for retention of foetal membranes was increased. The present study demonstrates that the ultrasonographic technique is a suitable method for the control of the uterine involution and for the diagnosis of pathological aberrations in sheep.