Rectal Prolapse in Mares

Anal Mare

Mares are naturally polyestrous, meaning that they ovulate only at certain seasons of the year. To make sure a mare ovulates at its appropriate time, veterinarians often conduct rectal examinations. Most commonly this exam serves to evaluate gynecologic conditions; however, colic evaluation and investigation of undescended testicles may also necessitate such evaluations.

Rectal prolapses in horses usually result from conditions which cause tenesmus, such as dystocia, constipation, neoplasia, foreign body obstruction or urethral obstruction; sometimes there may be no obvious underlying cause. Rectal prolapses most frequently affect mares.

An Atlantic Veterinary College staff veterinarian observed large amounts of fecal matter protruding from her anus and diagnosed an extensive rectal prolapse shortly after foaling in a standardbred mare, who was very anxious and bleeding profusely. Their staff conducted a detailed rectal exam to ascertain its nature and severity before performing surgery on her immediately post foaling.

Exams involve lubricating one hand with petroleum jelly before inserting it carefully into the rectum to remove any manure from behind it. Next, the veterinarian feels each organ for size, softness and position before assessing an ovary’s tone (firmness) which helps determine if a mare is pregnant. Though ultrasound has become a standard diagnostic tool in large animal medicine, palpation remains an indispensable method for gathering key information.