Eversion and prolapse of the vagina, with or without prolapse of the cervix, occurs most commonly in cattle and sheep. A form of vaginal prolapse, different in pathogenesis, also occurs in dogs (see Vaginal Hyperplasia in Small Animals). In cattle and sheep, the condition is usually seen in mature females in the last trimester of pregnancy. Predisposing factors include increased intra-abdominal pressure associated with increased size of the pregnant uterus, intra-abdominal fat, or rumen distention superimposed upon relaxation and softening of the pelvic girdle and associated soft-tissue structures in the pelvic canal and perineum mediated by increased circulating concentrations of estrogens and relaxin during late pregnancy. Intra-abdominal pressure is increased in recumbent animals. Added to this, sheep tend to face uphill when lying down, so gravity contributes to vaginal eversion and prolapse. Docking the tails of lambs may damage structures that support the pelvic girdle (eg, coccygeus muscle) and predispose to vaginal prolapse if the tail is docked too short. The tail should be removed at the level of the ventral skin fold, leaving two or three coccygeal vertebrae intact.
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