The Role of Computed Tomography in Equine Enterolithiasis: Insights from a Whole-Body CT Case Study

Advances in equine diagnostic imaging continue to expand the clinician's ability to diagnose complex gastrointestinal disorders. A notable example is the application of whole-body computed tomography (CT) in horses with enterolithiasis, providing detailed information that conventional radiography cannot always deliver. 

Why CT Matters in Enterolithiasis 

Traditional abdominal radiography can often detect enteroliths, but it may not accurately determine their exact size, number, or relationship to surrounding intestinal structures. This limitation becomes particularly important when surgical intervention is planned¹. 

The development of large-gantry CT systems has made it possible to perform whole-body imaging in selected equine patients, offering a new level of diagnostic precision. 

A Clinical Case: An 18-Year-Old Pony 

An 18-year-old pony presented with chronic anorexia, poor body condition, and weight loss. Initial abdominal radiographs identified a dense oval structure within the abdomen that was consistent with an enterolith¹. 

To obtain more detailed information, clinicians performed whole-body CT under general anesthesia using a large-bore multidetector scanner. Imaging was acquired with the horse in both prone and supine positions. 

What CT Revealed 

The CT examination provided several important findings that influenced surgical planning. 

Accurate Localization 

The enterolith measured approximately 100 mm and was located within the large dorsal colon. Positional imaging demonstrated that the weight of the enterolith caused displacement of the colon within the abdominal cavity, changing its orientation depending on whether the horse was positioned prone or supine. 

Identification of Intestinal Displacement 

Changing patient position allowed clinicians to visualize gravity-related movement of the gastrointestinal tract and better understand the true anatomical relationships before surgery. 

Detection of a Foreign Body Core 

One of the most striking findings was the identification of a high-density structure at the center of the enterolith. CT suggested the presence of a metallic foreign body, later confirmed after surgical removal. Three-dimensional reconstruction revealed a structure resembling a staple embedded within the stone. 

Surgical Benefits of Preoperative CT 

The information obtained from CT significantly improved surgical preparation^1,2. 

Better Understanding of Anatomy 

Knowing the precise location of the affected colon segment reduced exploration time during surgery and allowed surgeons to anticipate anatomical displacement before entering the abdomen. 

Accurate Assessment of Size 

CT provided precise measurements of the enterolith, helping surgeons determine whether manipulation through the intestinal tract would be possible or whether enterotomy would be required. 

Identification of Multiple Enteroliths 

Approximately 40% of horses with enterolithiasis may harbor multiple enteroliths¹. CT enables clinicians to evaluate the entire abdomen and identify additional stones that may be missed with conventional radiography. 

Surgical Outcome¹ 

During celiotomy, surgeons confirmed the CT findings and removed a 104 mm enterolith weighing 422 g from the large dorsal colon. Mineral analysis demonstrated a composition of approximately 50% magnesium ammonium phosphate and 50% calcium phosphate. 

The horse recovered uneventfully, regained appetite, and increased body weight from 158 kg to 205 kg within six months after surgery. 

Future Applications of Whole-Body CT 

This case highlights the growing value of advanced imaging in equine gastrointestinal surgery. Whole-body CT not only improves identification of enterolith location, size, and number but also provides critical information regarding intestinal displacement and potential foreign-body niduses. 

As access to large-bore CT systems increases, this technology may become an increasingly valuable adjunct for the diagnosis and surgical management of complex equine colic cases involving enterolithiasis. 

References

1. Nakamae Y, Ishihara A, Itoh M, Yanagawa M, Sasaki N, Yamada K. Displacement of the large colon in a horse with enterolithiasis due to changed positions observed by computed tomography. Journal of Equine Science. 2018;29(1):9-13. https://www.jstage.jst.go.jp/article/jes/29/1/29_1728/_pdf
2. Taylor CJ, Peter VG, Coleridge MO, Bathe AP. Immediate pre-operative computed tomography for surgical planning of equine fracture repair: A retrospective review of 55 cases. Plos one. 2022 Dec 28;17(12):e0278748. https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0278748&type=printable