Postpartum mares face a higher risk of developing large colon volvulus—a life-threatening type of colic in which the colon twists 360 degrees or more, cutting off blood flow and blocking the passage of gas and feed. Jesse Tyma, DVM, Dip. ACVS, a surgeon at Rhinebeck Equine, in New York, described the diagnostic and treatment approaches to this condition at the 2025 Cavalcade Education Equine Reproduction Seminar, held in Red Hook, New York, on Jan. 8.

Anatomy and Susceptibility in Postpartum Mares

Tyma described the large colon as a partially mobile gastrointestinal organ prone to displacement and twisting within the horse’s abdomen. The reason postpartum mares are especially susceptible to this condition relates to the empty space left in the abdomen after foaling, which allows the colon to shift more easily.

Diagnosing Large Colon Volvulus in Mares

The clinical signs of colic in a mare with large colon volvulus are usually severe, including vigorous pawing, violent rolling, a bloated appearance, and intractable discomfort. Tyma emphasized that prompt diagnosis and treatment are critical to the mare’s survival and foal’s safety.

“The colic exam aims to assess the postpartum mare’s overall health status, localize the lesion, and differentiate between a volvulus involving ischemia (lack of blood flow leading to oxygen deprivation and tissue death) and a displacement or other type of colic where the blood supply is unaffected,” said Tyma. “Diagnostics may include palpation per rectum, passing a nasogastric tube to check for gastric reflux, abdominal ultrasound to evaluate the colon wall and vasculature positioning, and bloodwork to measure lactate levels (which can signal severe tissue damage and the need for urgent intervention) and assess overall systemic health.”

Tyma also stressed the need to carefully assess the reproductive tract in the immediate postpartum colicky mare to rule out life-threatening hemorrhage, the clinical signs of which can overlap with those of large colon volvulus.

Treating Large Colon Volvulus in Mares

If a veterinarian strongly suspects large colon volvulus, the mare will likely need emergency colic surgery. “The goals of surgery are to characterize the lesion, manually correct the volvulus, and assess bowel viability to guide surgery decisions,” said Tyma. The surgeon might also perform a colon resection (the damaged tissue can be removed, and the healthy ends of the intestine stitched back together) or colopexy (creating an adhesion to the body wall to prevent future displacements and torsions), she added.

Postoperative Care and Complications

Beyond the risks of surgery and general anesthesia, recovery from large colon volvulus surgery involves intensive care because these mares often become systemically compromised and can decline quickly. “The postoperative patient requires close monitoring with serial examinations, multimodal pain management, fluid therapy, broad-spectrum antimicrobials, digital cryotherapy (icing the legs), supportive care, and a gradual reintroduction of feed,” Tyma said.

She added that common postoperative complications can include endotoxemia (toxin release into the bloodstream), diarrhea, recurrent colic, surgical site infection, and the painful hoof condition laminitis. “Transitioning the accompanying foal to a nurse mare is often recommended to lessen the physiologic demand on mares early in the postpartum period.”

Prognosis for Large Colon Volvulus in Mares

“In the best of clinical scenarios, the short-term prognosis for large colon volvulus is excellent, with survival rates reported up to 90%,” Tyma said. “However, in studies representing a broad population with variable referral access (to a surgical facility), the short-term survival rate is just 71%, with long term survival dropping to less than 50% by one year postoperatively. This speaks to the importance of quick referral and management for successful outcomes.”

Sixty-seven percent of mares treated for large colon volvulus produce at least one foal postoperatively. “The risk of recurrence of large colon malposition (inclusive of both surgical correction of displacement and volvulus) is 15%, and, following two occurrences of volvulus, the recurrence rate jumps to 80%, which is significant,” Tyma said. “Mares with recurrent volvulus that are intended to continue as broodmares should be considered candidates for a prophylactic procedure (colopexy or large colon resection) to reduce the risk of recurrence.”

Take-Home Message

Large colon volvulus presents a true emergency in postpartum mares, demanding rapid diagnosis, aggressive treatment, and intensive postoperative care. Tyma emphasized the importance of prompt referral to a surgical facility and potentially prophylactic procedures such as colon resection or colopexy in high-risk mares to reduce the risk of recurrence. “Prognoses for survival and continuation of reproductive careers can be good to excellent but remain dependent upon quick recognition of the condition, immediate action, and appropriate surgical and postoperative management,” she said.