Age is associated with the requirement for surgery in horses with nephrosplenic ligament entrapment of the large colon at a single UK equine referral hospital.

Background: Conservative and surgical management of left dorsal displacement and nephrosplenic ligament entrapment of the large colon (NSLE) is well described in horses. Whilst breed factors predispose the development of NSLE, it is unknown if breed affects the likelihood for surgical intervention.

Objectives: To compare the incidence of surgical intervention and differences in pre-operative parameters between Thoroughbred and non-Thoroughbred horses. The authors hypothesise a higher proportion of Thoroughbreds require surgical intervention.

Study design: Retrospective cross-sectional study.

Methods: Case records at a single equine referral hospital were searched between January 2007 and September 2022 for horses with suspected or confirmed NSLE on transrectal palpation, transabdominal ultrasonography or exploratory laparotomy. Horses were classified into Thoroughbred and non-Thoroughbred groups. Unpaired T-tests, Mann-Whitney U tests, Chi-squared tests and multivariable analysis were used to compare groups. A mixed effects multivariable logistic regression model compared surgery or conservative management as outcome variables.

Results: A total of 179 NSLEs in 169 horses were included (100 Thoroughbreds). Forty-eight horses (26.8%) underwent surgery, including 34 Thoroughbreds (70.8%). A total of 131 NSLEs in 125 horses were treated conservatively (73.2%), including 66 Thoroughbreds (50.4%). Univariable analysis showed Thoroughbreds were more likely to require surgical intervention compared with non-Thoroughbred breeds (odds ratio [OR] = 2.5; 95% confidence interval [CI] 1.03-6.18; p = 0.04). Thoroughbreds requiring surgical intervention were significantly younger than those treated conservatively (surgical group median = 2 years [interquartile range, IQR = 1], conservative group median = 4.5 years [IQR = 7], 95% CI 1.66-5.27 years; p ≤ 0.0001). Multivariable analysis, however, showed decreasing age alone was associated with an increased likelihood of surgical intervention (OR = 0.9; 95% CI 0.81-0.99; p = 0.03).

Main limitations: Definitive diagnosis of NSLE is not possible in conservatively managed cases.

Conclusions: For this hospital population, Thoroughbreds were more likely to require surgical correction of NSLE, most likely due to the significantly increased likelihood of surgical intervention in young horses.