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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • A laceration of the perineal body
  • First-degree laceration involves the mucosa of the vestibule and the skin of the dorsal commissure of the vulva
  • Second-degree laceration involves both the mucosa and the submucosa of the dorsal vulva and part of the musculature of the perineal body (constrictor vulvae muscle)
  • Third-degree laceration involves full-thickness tears through the perineal body, extending through the rectal wall and anal sphincter
  • RVVFs are full-thickness tears through the rectal wall and, possibly, involving the perineal body, but not involving the anal sphincter or vulva
  • Recto-vestibular fistulas are much more common than RVFs

Pathophysiology!!navigator!!

  • Perineal lacerations occur at parturition because of abnormal posture or position of the fetus, which predisposes the fetal extremities to be pushed more dorsal than normal, thus forcing the fetus's feet into and/or through the wall of the vagina or vestibule
  • Although rare, an oversized fetus may be a cause
  • Lacerations of the rectum or vagina can occur at breeding, but perineal lacerations are rare at this time
  • Recto-vestibular fistulas can result from an unsuccessful surgical repair of a third-degree perineal laceration
  • Mares with perineal lacerations or an RVVF are predisposed to recurrent uterine infections due to destruction of the anatomic structures (physical barriers) preventing contamination of the vagina

Systems Affected!!navigator!!

Reproductive

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

  • No statistics available regarding incidence
  • Common lesions in broodmares

Signalment!!navigator!!

  • All breeds
  • Maiden mares are more predisposed to these injuries during parturition

Signs!!navigator!!

General Comments

  • The condition is not an emergency
  • Because of the tearing, bruising, and edema occurring at and after injury, surgical correction of these lacerations is delayed until the initial inflammation has subsided and laceration has healed by second intention; generally at least 30 days

Historical Findings

  • Dystocia is common but not necessary
  • Because of the excessive force generated by the abdominal musculature (active labor), it is possible for a mare to deliver a live foal unassisted while creating a perineal laceration

Physical Examination Findings

  • Careful physical examination of the perineum, perineal body, vagina, and rectum
  • Transrectal palpation and vaginal examination

Causes!!navigator!!

  • Abnormal posture or position of the fetus at parturition
  • Fetal extremities are pushed more dorsal than normal within the birth canal, such that they penetrate and damage maternal soft tissue structures within the vagina, vestibule, and/or rectum

Risk Factors!!navigator!!

  • Dystocia—abnormal fetal position or posture, fetal oversize
  • Small vulva and tight vestibulo-vaginal sphincter
  • Because fetal posture and position can change within minutes before parturition, examinations conducted much before parturition are of little value
  • Failure to open the vulva (Caslick's vulvoplasty; an episioplasty) prior to foaling in mares

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Diagnosis is self-evident.

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

N/A

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

  • Partial to full-thickness lacerations of the vestibule, vagina, anal sphincter, and/or rectum
  • Aspiration of air into the vagina and/or uterus secondary to damaged normal barrier tissues, e.g. vulvar lips; vestibular sphincter
  • Fecal contamination of the vagina and vestibule, followed by inflammation of the vestibule, vagina, cervix, and, possibly, the endometrium

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • Confirm whether the laceration extends into the peritoneal cavity, a rare occurrence with perineal laceration or RVF
  • Systemic antibiotics seldom are indicated or necessary to control infection in this area; client education is imperative
  • Local medication rarely is indicated
  • Repair lacerations before attempting to rebreed
  • Boost tetanus vaccination, if not recent

Nursing Care!!navigator!!

N/A

Activity!!navigator!!

No restrictions.

Diet!!navigator!!

No restrictions.

Client Education!!navigator!!

  • Advise regarding the importance of close/frequent observation of foaling mares
  • Many lacerations occur before a problem is detected, even in the presence of trained foaling attendants

Surgical Considerations!!navigator!!

General Comments

  • Surgical repair is delayed until local inflammation and bruising have subsided (generally 4–6 weeks)
  • Imperative after surgery that feces remain soft until healing is complete. Mare should be given oral mineral oil prior to surgery
  • Early in the spring (preoperative), place the mare on pasture, and return it to pasture immediately after surgery. Green grass has a high moisture content, which should soften stool
  • Other methods of stool softening include bran and mineral oil
  • Several surgical techniques have been described for repair of third-degree perineal lacerations and RVVF. The success rate is highly dependent on the surgeon's experience

2-Stage Repair

Stage 1

  • Epidural anesthesia and sedation of the mare
  • The tail is wrapped and elevated over the mare and attached to a support directly above the animal
  • The rectum and vagina/vestibule are emptied of feces and thoroughly but gently cleaned. Use of irritating scrubs could stimulate postoperative straining and is contraindicated
  • Reconstruction of the perineal body:
    • An incision is made into the remaining shelf ≅2–3 cm anterior to the cranial limit of the laceration
    • The incision is continued posteriorly along the sides of the existing laceration in a plane approximately equal to the original location of the perineal body
    • The vestibular and vaginal mucosa is reflected ventrally ≅2 cm
    • Simple interrupted sutures are placed through the area of the perineal body so that the perineal body is reapposed and the submucosal vaginal or vestibular tissue is brought together in the same suture pattern
    • After placement of 1 or 2 of these sutures, a continuous suture pattern is begun in the reflected mucosal membrane to oppose the submucosal surfaces
    • This suture pattern continues cranial to caudal, as additional simple interrupted sutures are placed

Stage 2

  • Completed after healing of stage 1
  • Debride the anal sphincter and dorsal vulvar commissure, and place sutures in these tissues to reestablish the sphincters, if possible
  • Optimal success is achieved if sphincter tone is regained after repair

1-Stage Repair

Similar to 2-stage repair, except that repairs of the anal sphincter and dorsal vulvar commissure are completed at the time of the initial surgery.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Systemic antibiotics may be indicated immediately after laceration to prevent possible systemic involvement, but the laceration must be quite severe to warrant their use
  • Medications specific to accomplish the surgical repair
  • Ensure adequate tetanus prophylaxis

Contraindications!!navigator!!

N/A

Precautions!!navigator!!

N/A

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

Any agent designed for sedation and analgesia can be used during surgical correction.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • An immediate examination is indicated with the possibility or concern that a laceration has occurred
  • If its presence is confirmed but it does not extend into the perineal cavity, reexamine the area in ≅2 weeks to assess the degree of inflammation and formation of granulation tissue at the laceration site

Prevention/Avoidance!!navigator!!

  • Occurrence is difficult to predict
  • Close monitoring of mares (particularly maiden mares) during parturition

Possible Complications!!navigator!!

  • Abscesses may develop in the laceration area, but this is uncommon, aided in part by the abundant surface area that facilitates drainage and formation of granulation tissue from the deeper layers outward
  • If the laceration is sutured immediately after the occurrence, the potential for abscessation may actually increase

Expected Course and Prognosis!!navigator!!

  • Without surgical correction, mares with third-degree lacerations and an RVF have a very low probability of conceiving and maintaining a pregnancy to term
  • Therefore, surgical correction is strongly recommended before attempting breeding
  • Dehiscence and recto-vestibular fistula are possible complications requiring a second intervention

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

Occurs at parturition.

Synonyms!!navigator!!

N/A

Abbreviations!!navigator!!

  • RVF = recto-vaginal fistula
  • RVVF = recto-vaginal-vestibular fistula

Suggested Reading ⬆ ⬇

Aanes WA. Surgical repair of third degree perineal lacerations and recto-vaginal fistulas in the mare. J Am Vet Med Assoc 1964;144:485–491.

Belknap JK, Nickels FA. A one-stage repair of third-degree perineal lacerations and rectovestibular fistula in 17 mares. Vet Surg 1992;21:378–381.

Climent F, Ribera T, Argulles D, et al. Modified technique for the repair of third-degree rectovaginal lacerations in mares. Vet Rec 2009;164:393–396.

Colbern GT, Aanes WA, Stashak TS. Surgical management of perineal lacerations and recto-vestibular fistulae in the mare: a retrospective study of 47 cases. J Am Vet Med Assoc 1985;186:265–269.

Heinze CD, Allen AR. Repair of third-degree perineal lacerations in the mare. Vet Scope 1966;11:12–15.

McKinnon AO, Jalin SL. Surgery of the caudal reproductive tract. In: McKinnon AO, Squires EL, Vaala WE, Varner DD, eds. Equine Reproduction, 2e. Ames, IA: Wiley Blackwell, 2011:2545–2558.

Author(s) ⬆

Author: Ahmed Tibary

Consulting Editor: Carla L. Carleton

Acknowledgment: The author and editor acknowledge the prior contribution of Walter R. Threlfall.