Recovering from Dystocia: Repair of the Mare

Normal equine parturition or dystocias can result in serious trauma to the mare’s urogenital or  gastrointestinal tract. An understanding of some of the potential problems that can develop is  important to consider when doing dystocias. Equine practitioners should be familiar with the  initial management and treatment options available for particular injuries. The following  proceedings will describe some of the possible injuries that can occur and potential management  plan for each injury.  

Perineal Lacerations  

Perineal lacerations can occur commonly after parturition or dystocia.^1-3 I describe in more depth  the surgical techniques in the proceedings on “Reconstructive Surgical Procedures to Enhance  Mare Fertility”. I included a brief description here to detail the initial management of perineal  tears. There are three degrees of perineal lacerations.^1-3 First-degree lacerations involve the  vaginal mucosa. Second degree of perineal lacerations involve the vaginal mucosa and perineal  body, but does not involve the rectal vaginal shelf. Third degree perineal laceration does disrupt  the rectal vaginal shelf and there is communication between the vulva and rectum. This  classification does not include rectal-vaginal fistulas, which involve a communication between  the vulva/vagina and the rectum, but the anal sphincter is not disrupted (Fig. 1).
 

First and second degree perineal lacerations are initially treated medically. The laceration is  gently cleaned daily and very mild antiseptics should be applied. The prognosis is very good for  second-intention healing. If a second-degree perineal laceration is large enough and has healed  by conservative management, a Caslick’s technique may be needed to repair the perineal body. If  the laceration has disrupted the perineal body extensively, a Gadd technique may be needed to  improve the overall conformation of the perineal body.¹ A Gadd technique involves closure of  the dorsal vestibule after two large triangular flaps of mucosa, which connect dorsally, have been  removed. Removal of the mucosal flaps can be removed using local anesthesia. The defect  created by removing the mucosa is then sutured closed to appose the dorsal aspect of the vulva.  

Third degree perineal lacerations can be quite extensive initially and be associated with a  moderate amount of blood loss. As with first and second degree perineal lacerations, these  lacerations are initially treated medically. An attempt to immediately surgically close third  degree perineal lacerations or rectovaginal fistulas can be performed, but I have had poor results  and most repairs result in dehiscence. Perineal lacerations typically respond quite favorably to  medical management. Mares should be placed on broad spectrum antibiotics and nonsteroidal  anti-inflammatory agents for the first 3 to 5 days. I have seen a few mares develop severe septic  cellulitis in a hind limb secondary to third degree perineal lacerations requiring long-term  systemic antibiotics. With medical management, these lacerations can be gently cleaned daily  until there is evidence of granulation tissue or second intention healing. The mare’s vagina or  uterus can be lavaged daily to alleviate a vaginitis or metritis. Within the first 24 to 72 hours,  manual evacuation of the mare’s rectum may be required to alleviate rectal impactions resulting  from pain associated with defecation. Mares with third degree perineal lacerations or  rectovaginal fistulas may also require nasogastric intubation of mineral oil to potentially soften  the feces.  

Surgical repair is generally performed after the laceration has healed by second intention.  Smaller defects can be repaired as early as three to four weeks after the injury. However, larger  defects may require at least 6 to 8 weeks before attempting the surgical repair. Every case is  different and close monitoring of the injury is needed by the referring veterinarian prior to  making the decision for surgical repair. As a surgeon, I like to see the tissue with very little  edema or thickening prior to attempting the repair. The thickening is usually a result of the  edema in the tissue. A good indication the defect is ready for surgical repair is when the  thickness of the defect edge is similar to the thickness of the surrounding tissue about 3 to 4 cm  from the defect. For third degree tears, I try to digitally palpate the most cranial aspect of the  defect to determine tissue thickness. For most rectovaginal fistulas, the full circumference of the  defect can be digitally palpated. The method of repair can involve one or two stages and this  decision is generally based on surgeon preference. A one stage repair involves complete closure  of the rectal-vaginal shelf and perineal body. In a two stage repair, the rectal-vaginal shelf is  repaired initially, and then at least three to four weeks later, the perineal body is repaired to  complete the second stage. Generally the second stage can be performed using local anesthesia.  

Closure of the rectal-vaginal shelve can be performed using either two methods.^1-3 In both  methods, an incision is made to create a rectal shelf and a vaginal shelf on both the left and right  sides. The incision is generally through the demarcation of the rectum and vagina, but should  extend more into the vagina as the incision course caudally. This helps eliminate tension on the final repair. Shelves are created at the cranial aspect of the defect as well. It is important to  extend cranially about 2 to 4 cm when creating the shelves in the cranial aspect of the defect, and  the shelves on the sides should be undermined so that there is minimal tension on the closure.  The shelves can be closed using a simple continuous pattern in a cranial to caudal direction. The  vaginal side is closed first in 3 to 4 layers and then followed by the rectal side. Another method  involves moving in a cranial to caudal direction using an interrupted six-bite pattern to close both  the vaginal and rectal layers together.¹ In Lexington, the prognosis is generally very good for the  repair to stay together. However, we have the advantage of good green grass keeping the feces  soft in the spring. It is important to keep the feces soft so that the surgical repair does not  dehisce. Mineral oil may have to be given daily to help keep the feces soft in some cases. In  some cases, I try to decrease the intake of course roughage or I feed a predominantly pelleted ration.

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