Mare and foal survival and subsequent fertility of mares treated for uterine torsion

REASONS FOR PERFORMING STUDY: Previous surveys have reported mare and foal survival after correction of uterine torsion varies from 60-84% and 30-54%, respectively. Furthermore, resolution via a standing flank laparotomy (SFL) has been associated with better foal, but not mare, survival.

OBJECTIVES: To compare the success of SFL with other correction methods (e.g. midline or flank laparotomy under general anaesthesia; correction per vaginam).

STUDY DESIGN: Retrospective analysis of clinical records.

METHODS: Data on correction technique, stage of gestation, degree of rotation, survival and subsequent fertility for 189 mares treated for uterine torsion (UT) at 3 equine referral hospitals in the Netherlands during 1987-2007 were analysed.

RESULTS: Mean stage of gestation at diagnosis was 283 days (range 153-369) with the majority of UTs (77.5%) occurring before Day 320 of gestation. After UT correction, 90.5% of mares and 82.3% of foals survived to hospital discharge, between 3 and 39 days later, and to foaling. Multivariable logistic regression indicated that correction method and stage of gestation at UT affected survival of foals and mares. For foals, survival was 88.7% after SFL compared to 35.0% after other methods (P = 0.001). When UT occurred at <320 days, 90.6% of foals survived, compared to 56.1% at ≥320 days (P = 0.007). For mare survival, an interaction between stage of gestation and correction method was detected (P = 0.02), with higher survival after SFL (97.1%) than other methods (50.0%) at <320 days of gestation (P<0.01). When UT occurred at ≥320 days, mare survival did not differ between techniques (76.0% vs. 68.8; P = 0.6). Of 123 mares that were bred again, 93.5% became pregnant; fertility did not differ between mares treated by SFL (93.9%) and other techniques (87.5%; P = 0.9).

CONCLUSIONS: SFL is the surgical technique of choice for resolving uncomplicated (i.e. no co-existing gastrointestinal lesions) equine UT except when the stage of gestation exceeds 320 days.