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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2020) 32 (1) 22-24 doi: 10.1111/eve.12931
Clinical Commentary
Use of transabdominal ultrasonography in the acute abdomen: Has it really revolutionised our colic work-ups?
S. J. Waxman* Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, Indiana, USA *Corresponding author email:
swaxman@purdue.edu
Keywords: horse; colic; ultrasonography
Colic is one of the most economically important diseases affecting the horse industry and one of the most common reasons why horses present to a veterinarian as an emergency. It is the leading cause of death in equids between the ages of 1 and 20 years (National Animal Health Monitoring System (NAHMS) 2017). The equine practitioner is familiar with the routine colic work-up, which generally at minimum includes a physical exam, rectal exam and nasogastric intubation. While the majority of horses with signs of colic will respond to medical management, it is extremely important for the primary veterinarian to determine whether the horse can be treated medically, or if a recommendation for referral to a surgical facility should be made. The decision for surgery is primarily based on the degree
of abdominal pain, its ability to be controlled by medication and the results of examination and diagnostic tests. While uncontrollable pain alone can be reason enough to elect for exploratory laparotomy, if a horse’s comfort can be maintained then gastrointestinal specific tests should be performed and interpreted in an attempt to formulate an appropriate treatment plan. Does the horse have distended small intestine or significant gas distention of the large intestine on rectal exam? Does the horse have excessive gastric fluid? Does abdominocentesis yield fluid with abnormal parameters? The equine surgeon may be presented with a clear-cut case for surgery but it is not always that simple. The patient may be too small to safely undergo a rectal exam or the rectal exam may be unremarkable; no gastric reflux may be present; an abdominocentesis may not yield any fluid to evaluate or could be within normal reference ranges. When presented with a scenario such as this, the surgeon must look to ancillary diagnostic tests to determine the best course of action for the patient. One of the earliest articles reporting the use of ultrasound
in equine internal medicine was by Byars and Halley (1986). Their list of gastrointestinal diseases that could be evaluated included mostly those of the liver and spleen, but also included peritoneal effusions, ileus, and bowel displacements and distention, however specific conditions were not described in detail. Klohnen et al. (1996) first reported on the evaluation of
the use of transabdominal ultrasound in the equine colic patient. They determined that it was accurate for detecting small intestinal abnormalities and allowed quicker surgical intervention when other diagnostics were unremarkable. These authors did however state that abdominal ultrasound cannot identify the primary small-intestinal lesion. Although not the aim of the study, the authors did observe that horses having primary large-intestinal lesions did have large colon
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walls that were subjectively more distended and hyperechoic as compared with clinically normal horses; however, at that time they stated that other than for nephrosplenic entrapments, abdominal ultrasonography was non-diagnostic for primary large colon lesions. Since then, the quality of the ultrasound machine has
drastically improved and clinicians have become more experienced. Numerous articles have since been written on the subject, including review articles describing the complete abdominal ultrasound procedure to date (le Jeune and Whitcomb 2014), the development of the fast localised abdominal sonography of horses (FLASH) protocol (Busoni
et al. 2006), articles covering specific ultrasonographic findings relating to specific diseases (Bernard et al. 1989; Santschi et al. 1993; Taintor et al. 2004; Abutarbush 2006; Buchanan et al. 2006; Grenager and Durham 2011; Ness et al. 2012; Nielsen et al. 2016; Manso-Dıaz et al. 2018), and articles analysing the accuracy of ultrasonography in the colic patient (Beccati et al. 2011; Naylor 2015; Cribb and Arroyo 2018). le Jeune and Whitcomb (2014) presented a nice review
of how to perform a thorough abdominal ultrasound examination in the acute colic patient and provided very high quality images of common gastrointestinal abnormalities that could be present. Busoni et al. (2006) described the FLASH protocol. The goal of this protocol is to quickly evaluate a colic patient by evaluating seven different topographical locations. The mean time to complete the evaluation was 10.7 min and clinicians could successfully complete the protocol even without extensive ultrasound experience. The FLASH protocol was able to detect free abdominal fluid and abnormal intestinal loops. When dilated turgid small intestinal loops were found using this protocol, it had positive and negative predictive values of requirement for surgery at 88.89% and 81.48% respectively. Fairburn (2017) reviewed the literature to determine whether a fast scan (the FLASH protocol) has comparable sensitivity and specificity to a detailed exam for finding small and large intestinal lesions requiring surgery. It was concluded that the FLASH examination was indeed comparable, although some limitations in data precluded the ability to fully assess large intestinal conditions. The one concern was whether the FLASH technique would miss some cases of right dorsal displacement of the large colon due to the viewing window being more dorsal than the location of the vessels, which are often near the costochondral junction of the right body wall. Very specific ultrasonographic findings and how they
relate to a definitive diagnosis have been described throughout the literature including left dorsal displacement of the large colon (Santschi et al. 1993), small intestinal
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