Uterine torsion

Uterine torsion is a relatively infrequent condition of pregnant mares that can arise at any time after approximately 5 months of gestation, presumably the point beyond which the foal, when it turns, takes the uterus with it rather than rotating freely within the uterine lumen. True uterine torsion involves the rotation of the pregnant uterus about its long (cranio-caudal) axis by more than 180° (typically 270–360°) since, beyond this point, gravitational forces make spontaneous resolution very unlikely. Although the initiating causes of uterine torsion in the mare are not known, they have been postulated to include rapid rolling by the mare or vigorous fetal activity. Uterine torsion has also been proposed to be more common in larger breeds. In this respect, a survey of 189 cases of uterine torsion treated at 3 equine clinics in the Netherlands (Spoormakers and others, unpublished data) recorded 65% in Warmblood and 15% in Friesian mares; while this bias also broadly reflects the demographics of the patient populations at the clinics involved, the relatively high incidence of uterine torsion in the Netherlands does support a predilection for certain types or breeds. On the other hand, the survey did not yield any evidence for an age (mean age 9.1 years; mode 4 years) or parity (mean 4.1; mode 1) bias, and neither was there any indication that rotation was more common in one direction or the other (92/189 [49.2%] clockwise). It did, however, confirm that the majority of uterine torsions occur weeks to months prior to foaling (145/186 [78%] before 320 days of gestation), and relatively few at parturition.  […]