uterine tube obstruction in mares

Uterine tube, or oviduct, obstruction in mares, though rare, can cause subfertility. Diagnosing the condition is difficult; therefore, veterinarians typically do so by exclusion, said Stephanie Walbornn, DVM, Dipl. ACT. In other words, they suspect uterine tube obstruction after ruling out other causes for a mare’s subfertility using conventional diagnostic techniques.

While veterinarians have several methods for treating presumed uterine tube obstruction in mares, it’s been unclear how they affect future fertility. So Walbornn, of Rood & Riddle Equine Hospital in Wellington, Florida, compared pregnancy rates after practitioners performed two treatment methods for suspected uterine tube obstruction. She presented her findings at the 2018 American Association of Equine Practitioners Convention, held Dec. 1-5 in San Francisco, California.

The uterine tubes serve as reservoirs for deposited sperm, are the site of fertilization, and nourish the oocyte (egg) and embryo. If a mare is subfertile in the absence of ovarian and uterine abnormalities, and despite good reproductive management and stallion sperm quality, said Walbornn, veterinarians might suspect uterine tube pathology (disease or damage). Based on previous studies, mares become increasingly susceptible to this condition as they age, she added.

Walbornn described treatment options veterinarians might use in potential cases of uterine tube obstruction in mares:

  • Flushing the oviduct via laparotomy (abdominal incision);
  • Applying prostaglandin E2 (PGE2, a hormone that causes the oviduct to relax) laparoscopically (through small incisions and with the use of a laparascope) onto the surface of the uterine tube; and
  • Performing hysteroscopic hydrotubation (a procedure in which the veterinarian passes an endoscope into the uterus, catheterizes the uterine tube, and flushes it with saline).

Walbornn compared pregnancy rates after the latter two treatments and to help guide veterinarians and owners as to which procedure is best.

She looked at medical records of 69 mares ranging in age from 4 to 22 that had been barren for one year for no determinable reason. Thirteen of the 20 mares (65%) that received laparoscopic PGE2 application became pregnant, while 35 of 49 (71%) that underwent hysteroscopic hydrotubation became pregnant. Thus, Walbornn concluded that there was no significant difference in pregnancy rates between the two procedures, and veterinarians could perform either when faced with unexplained infertility from a suspected uterine tube obstruction.

She did note, however, that PGE2 application is more expensive, invasive, and requires more surgical skill than hydrotubation, but both can be performed under standing sedation.

“Make your decision based on comfort level with each procedure,” she said.