Third-degree perineal lacerations
Keywords: laceration, degree, mare, foaling, injuryFirst and second degree perineal lacerations are seldom of importance, the first being laceration of the vaginal mucosa and the second, laceration of the vaginal mucosa and the tissue between the vagina and rectum.
Third degree lacerations involve the vaginal mucosa, rectal mucosa, and the interposing tissue. They may take the form of fistulas or more commonly, complete destruction of the perineal body. As mentioned in an entry on evisceration after foaling these accidents appear to be more common in maiden mares than pluriparous mares. These old but valuable images illustrate the problem well.
In the top right inset of the image below, a third degree laceration is being examined several days after foaling. A large hematoma is present in the left wall of the vestibule and there is considerable fecal contamination over the lacerated tissue between the vagina and rectum. These injuries are almost never fatal and hemorrhage is seldom severe because of the blunt nature of this trauma.
The author estimates that the main image was obtained perhaps ten days later, when the hematoma had resolved and secondary intention healing of the torn tissue was well underway.
Image size: 840 x 767px Modified. Original copyright Dept. Theriogenology, ISU. Ames, Iowa.
Although the value of antibiotic treatment is debatable in these cases, immediately tetanus prophylaxis is suggested. Although there is some disagreement on when surgery should occur, the author suggests that one should resist the temptation to repair these injuries surgically until second intention healing is complete. If that is done, the wound margins and viable tissue can be clearly delineated for surgery.
In practice, the foal is also weaned before surgical repair is attempted because dietary restrictions imposed on the mare (to decrease fecal production) will retard the growth of the foal.
Owners may be concerned to wait for several month for repair because fecal contamination of the vagina continues during that period. Remarkably,this approach does not appear to have a detrimental effect on the future reproductive capacity of mares. This could be due to excellent uterine defense mechanisms in young mares,
Method of repair:
Image size: 743 x 824px Modified. Original copyright Dept. Theriogenology, ISU. Ames, Iowa.
The author has used an Aanes two-stage technique modified by Dr. Tracy Clark at Iowa State University. The image at upper left shows how the perineum has been prepared for surgery. Pre-surgical starvation diminishes the amount of feces in the rectum (ringed in the lower left inset) at the time of surgery. After all feces have been removed by hand, fecal debris can be prevented from entering the surgical field by using a large tampon device made of rolled cotton, held together with half hitches of umbilical tape, complete with a tail of tape to withdraw it from the rectum after surgery. Epidural anesthesia is used.
The inset image at lower right shows how the rectum, vagina and interposing tissue are repaired using a continuous, cranial-to-caudal suture pattern. No attempt is made to reconstruct the perineal body during first stage repair. Doing so will cause feces to exert pressure on the anus, breaking the suture line described above.
After the first stage has healed, the perineum is reconstructed.
Third degree lacerations of the perineal body may not involve the anus; after healing they take the form of fistulas between the vagina and rectum. Sometimes these fistulas are large, allowing these animals to defecate through their vulva lips. Such a case is shown below.
Image size: 444 x 1050px Modified. Original copyright Dept. Theriogenology, ISU. Ames, Iowa.
The lower image shows the area being prepared for surgery with a dramatic demonstration of the extent of the lesion to be repaired. The technique used is similar to the first stage described above.
The lower image shows the area being prepared for surgery with a dramatic demonstration of the extent of the lesion to be repaired. The technique used is similar to the first stage described above.
Reference:
Aanes, W.A. 1988. Surgical management of foaling injuries. Vet. Clin. North Am. Equine Pract. 4:417-438.
