All types of horses can get colic, but in the pregnant mare, the painful signs of colic might be caused by something other than a gastrointestinal problem. The mass of the foal and placenta causes a lot of crowding in the mare’s body, and uterine torsion–a twisted uterus–can be the result. But there is good news; a recent study found that at less than 320 days of gestation, chances are quite good that both mare and foal will survive uterine torsion with proper treatment. And there is a good chance the mare will be sound for future breeding after recovery.

Kristin Chaney, DVM, a resident at Michigan State University, described the study at the 52nd annual American Association of Equine Practitioners convention, held Dec. 2-6, 2006, in San Antonio, Texas. The retrospective study evaluated records of 63 mares with uterine torsion treated at four referral hospitals from 1985-2005, and it found a survival rate for mares of 84% (53 of 63 mares). “Two factors significantly affected survival: stage of gestation and heart rate at admission,” reported Chaney.

At more than 320 days of gestation, only 17 of 26 mares (65%) survived; she explained that at this stage, increased fetal size and weight complicate correction techniques. At less than 320 days of gestation, 97% of mares survived (one mare of 37 studied was euthanatized after a catastrophic accident during recovery). The study also found mares that survived had considerably lower heart rates than those mares that did not survive (59 beats per minute compared to 74 beats per minute). Although the data were not statistically examined, subjectively it didn’t appear that heart rate correlated with the degree of torsion or degree of pain, commented Chaney.

Overall foal survival rate was 54%. In those uterine torsion cases that occurred before 320 days of gestation, 72% of the foals survived (21 of 29) compared to 32% of foals (eight of 25) in pregnancies past 320 days. Ten mares aborted prior to discharge from the hospital and five full-term mares delivered live foals via Cesarean section at the time of correction (four of the foals survived). Of the 30 mares that went home pregnant and were available for follow-up, 25 had healthy foals.

Click here see the “plank in the flank” technique.

Three options exist for correcting torsions–ventral midline (belly) surgery, flank laparotomy (surgically accessing the uterus via flank incision with the mare standing and sedated), and rolling (putting the mare under general anesthesia and rolling her while the uterus is stabilized using a “plank in the flank” technique). The method used to correct the torsion did not statistically impact mare survival, but foals under 320 days of gestation had a better chance of surviving with flank laparotomy.

Chaney reported that some mares at more than 320 days of gestation were euthanatized following unsuccessful rolling and flank laparotomy procedures; increased size and weight of the fetus make these procedures more difficult and painful for the mare, particularly in the case of flank laparotomy, she said. “For these reasons, the authors feel that mare survival is optimized by correcting the uterine torsion under general anesthesia through ventral midline celiotomy (abdominal incision) when uterine torsion occurs at term gestation,” she noted.

As for mare reproductive health after correction, 67% of mares (24 of 36) were rebred successfully, 14% failed to become pregnant, and 19% were not rebred.

Chaney summarized the study findings as follows:

• Stage of gestation when uterine torsion occurs is important to foal and mare survival.
  
• Flank laparotomy is associated with improved foal survival at less than 320 days of gestation.
  
• If the mare is carrying a live foal at hospital discharge following correction of uterine torsion, it is highly likely that a term/healthy foal will be delivered.
  
• Future mare reproductive soundness after successful uterine torsion correction is good.

Get research and health news from the American Association of Equine Practitioners 2006 Convention in The Horse’s AAEP 2006 Wrap-Up sponsored by OCD Equine. Files are available as free PDF downloads