Etiology

• Poor vulvar conformation.
• Trauma.

Predisposing factors

General

• Advancing age.
• Poor body condition.
• Multiparity.
• Trauma to vulva, vestibule or perineal body during calving, and to a lesser extent mating .
• External trauma to vulvar labia.
• Poor tail-head, perineal fossa conformation.

Pathophysiology

• Vulvar lips cease to act as a seal   →   air, bacteria and other contaminated material (feces) enters   →   vaginitis   →   Endometritis  →   infertility.
• Poor vulvar conformation, eg vulva high in relation to pelvic brim and/or cranially sloping vulva, combined with other predisposing factors, especially age and multiparity   →   vulval lips cease to act as a seal   →   air aspirated into vagina and/or fecal contamination of vagina   →   vaginitis    →   ascending infection   →   endometritis →   subfertility or infertility.
• Some cases develop urinary tract infection (rare).
• Urovagina may develop in some cases, particularly when vulvar lips sutured ventrally so low as to obstruct exit of urine.
• Cows in poor Body condition Body condition  →   thin-lipped, toneless muscled vulva, absence of pelvic fat pads allows dorsal vaginal commissure to slope cranially.
• Vulvar defects often more apparent during estrus.
• Repeated trauma during calving, eg repeated stretching or laceration of vulva, vestibule or perineal body, Episiotomy Episiotomy  →   disrupt vulvar barrier by damaging underlying musculature.
• Older multiparous cattle   →   abdominal enlargement and stretching of mesometrium   →   splanchnoptosis   →   anus pulled cranially   →   distortion of perineum   →   vulva becomes stretched and tilted dorsocranially.
• Thin cattle, particularly heifers, may have vulval lips drawn forwards and decreased substance to labia and weak musculature.

Timecourse

• Chronic; conformational defect usually excabated by age.
• Traumatic cause - acute.