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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Urine reflux from urethral orifice into the vagina
  • Urine may then enter the uterus during estrus (relaxed cervix) or with cervical irritation
  • May cause infertility

Pathophysiology!!navigator!!

Altered position of the urethra in relationship to the vulvar cleft and vestibular sphincter; resulting in incomplete voiding or retention of urine in the vestibule/vagina.

Systems Affected!!navigator!!

Genetics!!navigator!!

Inherited predisposition for VC and, thus, the location of the urethral orifice.

Incidence/Prevalence!!navigator!!

Incidence may increase with age, parity, worsening VC.

Signalment!!navigator!!

  • All breeds, but most common in those with less perineal muscle
  • Greater problem in old pluriparous mares

Signs!!navigator!!

  • Few to no outward signs
  • Sole complaint may be infertility
  • On dismount, stallion may have urine evident on his penis
  • Transrectal examination and ultrasonography may disclose fluid within the uterus
  • Speculum examination may reveal pooled urine and increased hyperemia and ulcers (from urine scalding)—vaginal wall, external cervical os

Causes and Risk Factors!!navigator!!

  • With increasing age, dorsal vulvar commissure can shift cranially and/or dorsally (inward slant) coupled with a more cranial urethral opening and/or relaxation of the vestibule, urine refluxes into the cranial vagina
  • Inherited conformational traits
  • Multiparous

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Vaginitis
  • Pneumovagina

Imaging!!navigator!!

Ultrasonography showing liquid (urine) in the uterus.

Pathologic Findings!!navigator!!

  • Uterine/vaginal urine results in endometritis/vaginitis
  • Dorsal displacement of the external urethral os, cranial slant of the vulvae, and cranioventral/downward slant from the vagina to the cervix

Treatment ⬆ ⬇

TREATMENT

Surgical Considerations

Surgical repair—only permanent means of correction.

Pouret

Correction of inadequate VC by a caudal-to-cranial transection of the perineal body, separates the rectum from the tubular genital tract, allows the position of the vulva to lie more posterior and ventral, in tandem with posterior placement of the urethral orifice.

Urethral Extension

Posterior relocation of the urethral orifice by transverse splitting of the urethral fold—ventral shelf of the split tissue is brought to the midline and sutured, creates an extension of the urethra.

Monin Vaginoplasty

  • Ventral tissue dam of, or immediately cranial to, the vestibular sphincter to reduce the likelihood of urine entering the vagina
  • Limited success
  • May require repair after parturition

Medications ⬆ ⬇

MEDICATIONS

None

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Prevention/Avoidance!!navigator!!

  • None
  • VC is inherited

Possible Complications!!navigator!!

  • Infertility
  • Vaginitis

Expected Course and Prognosis!!navigator!!

  • Early recognition and treatment to avoid permanent vaginal/endometrial damage
  • Absent surgical correction, pooling continues
  • Until corrected, both inflammation and pooling continue

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

  • In the absence of systemic signs, no systemic therapy is justified and/or necessary
  • Flushing the uterus and vagina before insemination may increase the likelihood of conception but does not prevent subsequent urine accumulation and pregnancy loss
  • Pooling increases as uterine weight increases later in gestation; the vestibule is pulled more cranial and dorsal
  • If poor vulvar and vestibular conformation are secondary to loss of vaginal fat (e.g. mare that is cachectic, thin, poor conditioning), urine pooling may resolve as the mare gains weight:
    • Increasing fat within the pelvic cavity may elevate the vestibular floor in relationship to the ventral vulvar opening
    • This is considered to be a temporary solution, however, because the condition most likely will recur with age, parity, or subsequent weight loss

Associated Conditions!!navigator!!

  • Thin mares may be more predisposed to urine pooling
  • Usually most severe when the mare is in estrus and vestibular tissues are relaxed
  • Increased inflammation and fibrosis of the endometrium

Age-Related Factors!!navigator!!

  • Possible tendency for soft tissue supporting structures of the vestibule to decrease their tonicity with age
  • Increased incidence in older mares

Pregnancy/Fertility/Breeding!!navigator!!

May observe infertility or loss of pregnancy secondary to urine pooling.

Synonyms!!navigator!!

Vesicovaginal reflux

Abbreviations!!navigator!!

VC = vulvar conformation

Suggested Reading ⬆ ⬇

McKinnon AO, Beldon JO. Urethral extension technique to correct urine pooling (vesicovaginal reflux) in mares. J Am Vet Med Assoc 1988;192:647–650.

Schofield WA. Use of acupuncture in equine reproduction. Theriogenology2008;70(3):430–434.

Shires GM, Kaneps AJ. A practical and simple surgical technique for repair of urine pooling in the mare. Proc Am Assoc Equine Pract 1986;27:51–56.

Author(s) ⬆

Author: Carla L. Carleton

Consulting Editor: Carla L. Carleton

Acknowledgment: The author/editor acknowledges the prior contribution of Walter R. Threlfall.