Why Do Horses with Right Dorsal Displacement Experience More Post-Operative Colic?

For many horses, surgical correction of right dorsal displacement (RDD) results in a successful recovery. However, veterinarians have long recognized that horses with RDD appear more likely to experience recurrent colic and postoperative complications than horses with other non-strangulating large colon lesions (NSLC)¹. 

Post-Operative Challenges Following RDD 

Studies comparing horses with RDD to those with other large colon displacements have shown that RDD cases are more likely to develop severe postoperative complications. These complications often involve the gastrointestinal tract and may contribute to an increased risk of recurrent colic episodes. 

Common postoperative complications reported in colic patients include ileus, wound infection, incisional hernia formation, jugular thrombosis, repeat surgery, and recurrent abdominal pain¹. 

Recurrent Colic: A Persistent Concern 

Recurrent colic is among the most frequently reported long-term complications in horses undergoing surgery for RDD (2). 

Colic episodes can occur both before hospital discharge and months to years after surgery, emphasizing the need for long-term monitoring. 

Why Is Recurrence More Common? 

The exact reason for increased recurrence remains unclear, but several factors may contribute. 

Prolonged Obstruction and Inflammation 

Many horses with RDD experience mild obstruction for an extended period before referral. Prolonged colic can lead to congestion, edema, and inflammatory changes within the colon^2,3. 

Damage to Intestinal Pacemaker Cells 

Research has shown that chronic inflammation may disrupt interstitial cells of Cajal (ICC), the specialized pacemaker cells responsible for coordinating gastrointestinal motility. Reduced ICC density and decreased neuronal activity have been documented in horses with colonic disease¹. 

This dysfunction may persist even after surgical correction, potentially predisposing horses to future motility disorders and recurrent displacement. 

Increased Need for Repeat Surgery 

Horses with RDD are also more likely to require a second exploratory laparotomy than horses with other non-strangulating large colon lesions. Common findings during repeat surgery include ileus, motility disturbances, and recurrent displacement of the large colon. 

Although recurrence of RDD itself has been reported previously, many horses develop alternative forms of large colon displacement, suggesting that an underlying motility abnormality may be present¹. 

Does This Affect Long-Term Survival? 

Interestingly, despite a higher incidence of complications and recurrent colic, overall short- and long-term survival rates appear comparable to those of horses with other large colon lesions. Many horses successfully return to their intended use following recovery¹. 

However, owners should be informed about the increased likelihood of recurrent colic episodes and the potential need for future veterinary intervention. 

Clinical Implications 

The findings highlight the importance of early referral and prompt surgical decision-making in horses suspected of having RDD. Understanding that these cases may involve underlying motility disorders, inflammation, and gastrointestinal dysfunction can help practitioners better manage postoperative expectations and long-term care. 

Further prospective studies are needed to clarify why RDD cases experience higher rates of recurrent colic and to identify strategies that may reduce recurrence and improve long-term outcomes. 

References

1. Whyard JM, Brounts SH. Complications and survival in horses with surgically confirmed right dorsal displacement of the large colon. The Canadian Veterinary Journal. 2019 Apr;60(4):381. https://pmc.ncbi.nlm.nih.gov/articles/PMC6417614/pdf/cvj_04_381.pdf  

2. McGovern KF, Suthers JM, James FM, O'Meara BJ, Parker RA, Foote AK, Bladon BM. Gastric impaction associated with displacement and volvulus of the large colon in seven mature horses. Equine Veterinary Education. 2015 Sep;27(9):453-9. https://doi.org/10.1111/eve.12396
3. Blikslager AT. Gastric impaction and large colon volvulus: Can one lead to the other?. Equine Veterinary Education. 2015 Sep;27(9):460-1. https://doi.org/10.1111/eve.12417