Horses with diaphragmatic tears (also called rents) are given a relatively poor prognosis to make a full recovery, but the condition is not a death sentence, according to the results of a recent retrospective study. Alfredo E. Romero, DVM, of Syracuse Equine Veterinary Specialists in Manilus, N.Y., and colleagues found that the overall survival rate for horses presented with a diaphragmatic rent was 23%, and surgery to correct the rent produced only a 46% survival rate.

The diaphragm is an essential organ in the body that controls the horse's breathing. Diaphragmatic tears are "seldom diagnosed," said Romero in his study, and they are generally associated with trauma or congenital defects (i.e., there's little owners can do to prevent the occurrence of rents). When diagnosed, horses often present with signs of colic.

"Vague clinical signs are the hallmark of diaphragmatic herniation," he continued. "These include colic most often, but can also include tachypnea (increased respiratory rate, decreased respiratory volume). Additionally, tachycardia (increased heart rate) can also be observed and is most often associated with pain in general."

In the study Romero wrote that there "have been no substantial surveys of diaphragmatic rents or defects seen at referral hospitals," and most of the studies in the past have examined no more than six cases. For the current study, Romero and his team examined the records of 31 horses that were diagnosed with a diaphragmatic rent between January 2001 and June 2006 at Hagyard Equine Medical Center in Lexington, Ky., or the University of California, Davis, Veterinary Medical Teaching Hospital.

Of the 31 horses, 25 were adults (ages 1 to 28 years) and six were foals--all were diagnosed after presenting with clinical signs of colic. Twenty-eight of the cases presented were Thoroughbreds (22 adults and six foals), two were Quarter Horses, and one was an Arabian.

Twenty-five horses (19 adults and 6 foals) underwent an exploratory laparotomy (surgical incision into the abdominal wall).

He noted that good candidates for surgery are those whose blood flow is not compromised at the time of presentation.

"In addition to that, those animals that show minimal alterations to the abdominocentesis (belly tap) are also good candidates," he said. "Horses that are showing evidence of damaged or ischemic (decreased blood supply) intestine or show moderate to severe derangement in the bloodwork tend to have a decreased prognosis."

Of the 19 adult horses that were taken to exploratory surgery:

  • Five successfully had their diaphragmatic rents repaired with sutures;
  • Five were successfully corrected with the use of a polypropylene mesh in conjunction with the sutures.
  • Eight were euthanized on the table for "a variety of reasons" including the diagnosis of an irreparable diaphragmatic rent or a strangulated bowel; and
  • One underwent surgery, but it was deemed unsuccessful and the horse was euthanized within 24 hours of the surgery.

Seven of the ten horses that underwent successful surgeries are currently still alive and five are successful broodmares (two died of complications from surgery and one died of unknown causes).

In addition to the adult horses, six foals were taken to exploratory surgery:

  • Three of the rents found during surgery were corrected with sutures alone (two of which died in the postoperative period); and
  • Three were euthanized on the table due to the severity of the rents and associated hernias.

The surviving foal is now successfully performing as a racehorse.

Of the six horses that did not undergo surgery:

  • Five were euthanized before going to surgery (Romero cited economic constraints and poor long-term prognosis for survival or return to work); and
  • One was diagnosed with a diaphragmatic rent (via radiographs and ultrasounds) and was managed medically until stable, but was discharged at the owner's request and against the hospital's advice.

"While often the focus in these cases is the size and shape of the diaphragmatic defect and the ultimate correction, it appears that there are many other pertinent issues to consider when presented with such a case, such as the amount of types of viscera involved or degree of respiratory insult experience," Romero said in his study.

He added, "These horses are not delivered a death sentence by the diagnosis and for a percentage of these horses, the defect can be repaired and the horse can lead a productive life.

"The owner must understand that the prognosis is significantly lower than with other types of abdominal surgery, but the prognosis is not a grave one, as once thought," he concluded.

The study, "Diaphragmatic herniation in the horse: 31 cases from 2001 to 2006," was published in the November 2010 issue of the Canadian Veterinary Journal. The abstract is available on PubMed.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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