Presurgical radiographic visualization of colonic displacement in horses suspected of sand impaction colic

Background: Sand colic is a common cause of morbidity and mortality in horses. The prognosis depends on the moment when it is detected and at what point which treatment is initiated. Medical treatment is successful in most horses with sand accumulations, but sometimes surgical intervention is necessary. Horses with persistent colic despite medical treatment are likely to have a concurrent gastrointestinal lesion (Hart et al. 2012). An increased accumulation of gas on radiographs and abnormal transrectal examination findings are associated with an increased likelihood of the need for surgery (Kilcoyne et al. 2017). 25%–54% of horses that undergo surgery for sand colic have a concurrent large colon torsion or displacement (Granot et al. 2008). Abdominal radiographs are considered the gold standard for diagnosing sand accumulation in horses. In addition to the presence of sand, abdominal radiography can be used to determine the number and size, location, opacity and homogeneity of sand accumulation, which are all useful parameters when diagnosing sand colic (Korolainen & Ruohoniemi 2002, Keppie et al.2008). On radiographs, the shape of accumulations can vary greatly (Ruohoniemi et al. 2001). Whether or not it is possible to diagnose colon torsion or displacement on abdominal radiographs has yet not been clearly reported in literature. Objectives: The aims of this study were to determine if it is possible to diagnose colon torsion or large colon displacement on abdominal radiographs in horses with sand accumulation/colic and to determine agreement between presurgical rectal palpation, abdominal radiographs and surgical findings. Methods: Included were horses that had undergone colic surgery at the Equine teaching hospital from 2018 to 2023 and had presurgical abdominal radiographs available to evaluate the presence of sand. Patient records were collected and the radiographic findings were compared to the findings on rectal palpation before surgery and the surgical findings, performed and recorded by veterinary diagnostic imaging specialists (ECVDI), equine internal medicine specialists(ECEIM) and veterinary surgeons (ECVS) respectively. Results: Abdominal radiographic reports of examinations performed less than 24 h before colic surgery in 23 horses were retrieved. The group consisted of 15 mares, 2 stallions and 6 geldings, with a mean age of 10.8 years (3 months-25.5 years), and mean bodyweight of425 kg (120–633 kg). During surgery, 13 horses were diagnosed with a colon torsion or displacement (6 colon torsions, 5 right dorsal dis-placements, 1 retroflexion and 1 inguinal entrapment of the ascending colon). 20 horses survived surgery (87.0%) and 16 survived to discharge (69.6%). The number of horses that survived surgery with or without a colon torsion or displacement was 84.6% (11/13) and90% (9/10) respectively. Survival to discharge was 76.9% (10/13)and 60% (6/10) respectively. Of the horses that did not survive to discharge, 42.9% (3/7) had a colon torsion. 50% (3/6) of the horses with a (partial) colon torsion did not survive to discharge, of which 2horses were euthanised during surgery. In 4 horses, rectal palpation before surgery was not possible or very limited due to the size of the horse/pony or severity of colic signs, and in 8 horses the findings on rectal palpation did not agree with the surgical findings. In 3 horses, a displacement was not diagnosed by rectal palpation (2 right dorsal displacements and 1 colon torsion) and in 5 horses, a displacement was suspected by rectal palpation, but not present during surgery. On presurgical radiographs, 12 horses had no sand or only a mini-mal amount and 11 horses had a clinically relevant amount of sand accumulation. In 8 horses with sand accumulations, an abnormal position of the large intestines was suspected based on abdominal radiographs and 6 of these cases matched the surgical findings. The7 horses with surgical diagnosis of colonic displacement that was not suspected on presurgical radiographs, all had minimal to no sand. For 19 horses, both presurgical rectal palpation and abdominal radiographs were available, but in 4 horses presurgical rectal palpation was not performed. An agreement between rectal palpation, abdominal radiography and abdominal surgery was found in 31.6% (6/19),between rectal palpation and abdominal radiography in 47.4% (9/19),between rectal palpation and surgery in 57.9% (11/19) and between abdominal radiography and surgery in 60.9% (14/23) of cases. Conclusions: Displacement of the large colon can be seen on abdominal radiographs of horses with sand accumulations. There was a better agreement between the radiographic and surgical diagnosis than between rectal palpation and the surgical diagnosis. Therefore, abdominal radiography might be a useful addition to the workup of a horse with/suspected of sand colic.