Prolapse of the uterus may occur in any species; however, it is most common in dairy and beef cows and ewes and less frequent in sows. It is rare in mares, bitches, queens, and rabbits. Invagination of the tip of the uterus, excessive traction to relieve dystocia or retained fetal membranes, uterine atony, hypocalcemia, and lack of exercise have all been incriminated as contributory causes.
Prolapse of the uterus invariably occurs immediately after or within several hours of parturition, when the cervix is open and the uterus lacks tone. Prolapse of the postgravid uterine horn usually is complete in cows, and the mass of uterus usually hangs below the hocks. The invagination of the contralateral horn, which is prevented from exteriorization by the strong intercornual ligament, can be located by careful examination of the surface of the prolapsed organ. In sows, one horn may become everted while unborn piglets in the other prevent further prolapse. In small animals, complete prolapse of both uterine horns is usual. A contributory cause in sheep may be grazing estrogenic pastures.
In cows, treatment involves removing the placenta (if still attached), thoroughly cleaning the endometrial surface, and repairing any lacerations. Rubbing the surface of the uterus with glycerol helps reduce edema and provides lubrication. The uterus is then returned to its normal position. An epidural anesthetic should be administered first. If the cow is standing, the cleansed uterus should be elevated to the level of the vulva on a tray or hammock supported by assistants, and then replaced by applying steady pressure beginning at the cervical portion (or at the level of the invagination of the nonprolapsed uterine horn) and gradually working toward the apex. Once the uterus is replaced, a hand should be inserted to the tip of both uterine horns to be sure there is no remaining invagination that could incite abdominal straining and another prolapse. Installation of warm, sterile saline solution is useful to ensure complete replacement of the tip of the uterine horn without trauma. If recumbent, the cow should be positioned with the hindquarters elevated by placing her in sternal recumbency with the hindlegs extended backward. When elevating the hindquarters of the cow, care should be taken to lift the prolapsed uterus with the hindquarters to prevent stretching and laceration of the uterine artery.
Replacement of the prolapsed uterus in mares is done in a similar way, usually with the mare sedated but standing, taking care not to perforate the uterus.
In sows and small animals, the uterus may be repositioned by simultaneously manipulating it from outside with one hand and through an abdominal incision with the other. Resection of the uterus is indicated in longstanding cases in which tissue necrosis has occurred. Once the uterus is in its normal position, oxytocin (up to 5 IU, IV, or up to 20 IU depending on species, IM) is administered to increase uterine tone. Administration IV of calcium-containing solutions is indicated in most cases, also as a means of increasing uterine tone. Caslick sutures or other forms of vulvar closure are not useful, because the uterine prolapse begins at the apex of the uterine horn. Prevention of recurrence depends on complete and correct replacement of the uterus and restoration of uterine tone.
The prognosis depends on the amount of injury and contamination of the uterus. The prognosis is favorable when a clean, minimally traumatized uterus is promptly replaced. There is no tendency for the condition to recur at subsequent parturitions.
Complications tend to develop when laceration, necrosis, and infection occur, or when treatment is delayed. Shock, hemorrhage, and thromboembolism are potential sequelae of a prolonged prolapse. In some instances, the bladder and intestines may prolapse into the everted uterus. These require careful replacement before the uterus is replaced. The bladder may be drained with a catheter or needle passed through the uterine wall. Elevation of the hindquarters and pressure on the uterus aid in replacement of bladder and intestines. It may be necessary to incise the uterus carefully (in a longitudinal direction) to replace these organs. In cows, amputation of a severely traumatized or necrotic uterus may be the only way to save the animal. Supportive treatment and antibiotic therapy are indicated.