Retrospective review of uterine prolapse in mares

Uterine prolapse (eversion) is an infrequent but life-threatening emergency in mares. Since uterine prolapse is so uncommon, there is very little information published in scientific journals. Aim of this report is to describe uterine prolapse predispositions and case outcomes by reviewing clinical records from the UC Davis Veterinary Medicine Teaching Hospital (VMTH). Mare history and outcome data were analyzed for correlation to mare survival with Mann-Whitney U calculation and Fishers Exact Test. Significance level of p < 0.05 was set for all analyses. During 30 year period (1989 - 2019), 24 mares were presented with uterine prolapse. Age of mares ranged from 4 - 23 years (Mean  SD; 11.1  4.6) and parity ranged from 1 st to 13 th foaling (Mean  SD; 3  2.7). There was a high representation of maiden mares (7 out of 24). Investigation of interrelation between breed and uterine prolapse revealed that Arabians were overrepresented among affected mares compared to general breed distribution at the VMTH in the same time period. Uterine prolapse was associated with parturition and occurred within 1 hour after foaling in 82% of the cases. Fetal membranes were attached at the time of prolapse in 63% of the cases. Contrary to common belief that dystocia is the greatest predisposing factor to prolapse, only 33.3% of prolapses occurred after dystocia and 16.6% prolapses followed an abortion. Survival of the mares at discharge was 75%. Regarding fatalities, 5 mares suffered acute hemorrhage associated with prolapse and 1 died from secondary peritonitis. Fetal gender was overrepresented by males, 12 foals were colts and 5 were fillies (7 unknown). Fifteen foals survived. We were able to obtain follow-up history for 14 mares; 5 were rebred, and 4 foaled successfully. There were no correlations between mare survival and parity, age, sex of the foal, retained fetal membranes, or occurrence of sepsis. Based on the findings, we concluded that uterine prolapse occurred more after normal parturition (eutocia) than following abortions (16.6%) and dystocia (33.3%). Uterine prolapse may also have some breed predisposition to Arabians. Colts are overrepresented among affected mares. No characteristics were correlated with survival of mare, but severe hemorrhage was correlated with nonsurvival.

Keywords: Mare, uterine prolapse, normal parturition, abortion, dystocia

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.