Differences in uterine position of reproductively normal mares and those with delayed uterine clearance detected by scintigraphy.

The position of the uterus within the abdomen may affect a mare's ability to rapidly clear the uterine lumen of contamination. In this study, the position of the uterus was determined from left and right lateral flank scintigrams taken 1 and 2 h after intrauterine infusion of radiocolloid. Scintigraphy was performed during estrus in 44 mares, 24 were reproductively normal and 20 exhibited a delay in uterine clearance. Reproductively normal mares were nulliparous (n = 14) or pluriparous (n = 10), 3 to 21 yr of age, had no history of persistent uterine infections and cleared > 50% of a radiocolloid within 2 h of infusion into the uterus. Mares that exhibited a delay in uterine clearance were pluriparous (n = 18) or nulliparous (n = 2), 12 to 24 yr of age, had a history of endometritis and cleared < 30% of a radiocolloid within 2 h. The angle between the caudal-ventral aspect of the uterine image and cervix relative to horizontal as visualized on the scintigram was measured with a protractor. Results were analyzed by the General Linear Model System. The uterine-cervical angle relative to horizontal was more ventral in mares with delay in uterine clearance and was more horizontal in reproductively normal mares (mean +/- SEM-111.6 +/- 3.6 for delay in uterine clearance mares; 147.6 +/- 3.9 for reproductively normal mares; P < 0.0001). The mean angle for reproductively normal, pluriparous mares was steeper than that for nulliparous mares (141.1 +/- 2.9, 152.3 +/- 2.44 respectively; P = 0.004). There were no differences in angles between left and right lateral views within individuals. We conclude that a uterus that tilts ventrally in relation to the pelvic brim may contribute to the inability of delay in uterine clearance mares to rapidly clear their uterine lumen of contamination. Parity may contribute to the more ventral orientation of the uterus.