Equine Colic Diagnosis Via Palpation and Nasogastric Intubation: Part 2

Home , Exploratory laparotomy, Horse colic, Nasogastric intubation, Rectal examination

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Equine colic diagnosis via palpation and nasogastric intubation: part 2

Author : Sarah Freeman, Karen Rickards, Adelle Bowden, John Burford, Gary England

Categories : Equine, Vets

Date : September 26, 2016

The first part (VT46.36) of this two-part article reviewed the role of patient history and physical examination on decision making in horse colic and the use of diagnostic tests.

This part focuses on the two most commonly used diagnostic tests: abdominal palpation per rectum and nasogastric intubation. A survey of veterinary practitioners identified rectal examination was used in more than 75% of cases presenting with colic, and nasogastric intubation was used in more than 40% of cases1.

Abdominal palpation per rectum

Figure 1. Diagrammatic representation of the normal anatomical structures on the left side of the equine abdomen. Image: Boehringer Academy.

A large range of diagnostic tests exist for the investigation of horses presenting with colic, and the number and type of tests used by different practitioners varies significantly1,2.

Opinions vary as to whether every horse presenting with colic should have a rectal examination performed (where it is safe and practical), but it is the most commonly used and probably the most important diagnostic test.

The main factors restricting its use are the risk of injury (rectal tears) to the horse and risk of injury to the vet when performing the procedure, which may be particularly of concern in a field situation

1 / 8 with limited restraint facilities. The incidence of rectal tears in horses undergoing rectal examination for colic is not known, but is considered to be very low. Factors thought to be associated with increased risk are young/unhandled animals, and animals that are difficult to handle – either as a result of temperament or their level of pain.

A judgement must be made on the size and age of the patient, and alternative techniques, such as ultrasonography and radiography, considered in small and/or young animals3. The client should be actively involved in decision making, have an understanding of the procedure being performed, the reasons for its use, its limitations and potential issues, and the importance of adequate restraint prior to rectal examination being performed.

Figure 2. Diagrammatic representation of the normal anatomical structures on the right side of the equine abdomen. Image: Boehringer Academy.

Adequate restraint is essential in both the field and hospital environments. Physical restraint options include use of a twitch – lifting a foreleg, positioning the horse facing a solid wall (with sufficient space behind for the horse for safety during the examination), and bales of forage or bedding adjacent to and/or behind the horse. Horses should not be examined rectally over a stable door due to the risk of injury to the vet’s arm if the horse sinks down during the procedure.

Chemical restraint options include sedation with alpha-2 agonists, spasmolytics and analgesics. Acepromazine should not be used for sedation. The choice of alpha-2 agonist and the dosage used should be based on the required duration of action and any potential concerns over hypovolaemia. Doses of up to 0.5mg/kg of xylazine IV can be useful for short durations (15 to 30 minutes) to enable initial assessments and then re-evaluation of clinical signs. Detomidine or romifidine may be preferred if a longer duration of sedation is required for more prolonged procedures or transport of the patient.

The impact of chemical restraint on clinical parameters should always be considered. Alpha-2 agonists will cause a reduction in heart rate and respiratory rate, decreased gastrointestinal borborygmi and some visceral analgesia4,5. Where possible, this clinical data should be collected and assessed prior to drug administration.

2 / 8 Interpretation of rectal exam findings

Figure 3. Diagrammatic representation of the normal anatomical structure viewed from the caudal aspect of the equine abdomen. Image: Boehringer Academy.

Excellent descriptions of the examination technique and its interpretation exist in the literature6 and through online materials on commercial websites, such as www.boehringer-academy.co.uk

Interpretation of rectal examination findings should follow a similar approach to interpreting other diagnostic techniques, such as radiographs. This includes evaluating normal structures, describing the size, shape and nature of any abnormal findings, and then constructing a list of possible differentials. Normal anatomical features are described in Table 1 3,7 and shown in Figures 1, 2 and 3. A decision-making process for evaluating rectal examination is described in Figure 4.

Transrectal or transcutaneous ultrasonography can be a useful technique to confirm or add further information on abnormal findings on rectal examination, providing information on aspects such as the degree of intestinal distension, the nature of intestinal contents, thickness of the intestinal wall and the intestinal motility8. It can also be a valuable aid to confirm rectal findings to enable less experienced practitioners develop their skill and confidence in recognising different abnormalities, and is more sensitive and specific than rectal examination in detecting abnormalities9.

The main aim of rectal examination should be for identifying aspects that will alter the diagnostic or therapeutic approach to a case, rather than focusing a definitive diagnosis. Examples are the presence of distended small intestine on rectal examination, indicating nasogastric intubation is required, or the presence of a large colon impaction, indicating the need for treatment with oral fluid therapy.

3 / 8 Figure 4. Checklist for interpreting rectal examination findings in the equine colic patient.

Definitive diagnoses often require additional diagnostic tests, and rectal findings may not be specific for a number of conditions. A common misinterpretation is the diagnosis of left dorsal displacement or nephrosplenic entrapment based on rectal palpation. The presence of large intestinal tympany in the left caudal abdominal region (either primary or secondary to other conditions, including displacement and impaction) can impede the ability to palpate the nephrosplenic space and lead to false-positive diagnoses of nephrosplenic entrapment.

A definitive diagnosis requires positive findings on transcutaneous ultrasonography10. The other main limitation of rectal examination is the region of the abdomen that can be palpated. This is dependent on the size of the horse, but, in general, palpation is limited to the caudal third of the abdomen, and a number of conditions affecting the cranial abdomen (such as gastric and sternal flexure impactions, and some epiploic foramen entrapment cases) may have no palpable abnormalities.

4 / 8 Table 1. Palpable anatomical features of main abdominal organs in the horse.

Other diagnostic tests, including transrectal and transcutaneous ultrasonography, gastroscopy, laparoscopy and exploratory laparotomy, may be required in some cases.

Despite these limitations, rectal palpation remains one of the key diagnostic tests for horses with colic. It is the only technique that can definitively diagnose common large intestinal impactions, and this diagnosis will trigger different treatment plans to other types of colic11,12. It is also essential to identify the location of impactions: pelvic flexure and caecal impactions have markedly different prognoses in terms of outcome and, therefore, client advice and treatment approaches need to be adjusted accordingly13,14.

Rectal palpation should not be reserved just for cases showing more severe signs of colic or cardiovascular compromise. Small intestinal distension on rectal examination can provide one of the earliest indicators of surgical obstructions (prior to the onset of systematic signs associated with cardiovascular compromise), and early recognition and treatment of these cases impacts on outcome and prognosis (Figure 5)15.

Nasogastric intubation

Nasogastric intubation is performed in horses with signs of colic, both for diagnostic purposes, but also for administering enteral fluids and treatments. Similar issues exist around restraint of the horse and risk to personnel involved. The potential complications, particularly epistaxis, can be distressing to the owner, and, once again, the owner should have an active involvement in decision

5 / 8 making and an understanding of the reasons for performing this test and any potential complications.

Table 2. Indications for nasogastric intubation.

The anatomicº configuration of the gastro-oesophageal junction in the horse means gastric rupture is a significant risk in horses with proximal obstructions (including small intestinal strangulations, grass sickness, ileal impaction and gastric impactions). Nasogastric intubation is, therefore, an essential procedure in these cases, and indications for nasogastric intubation are outlined in Table 2. Presence of more than one or two litres of fluid in an adult horse should be considered abnormal and consistent with a proximal obstruction. Impaction of the stomach with solid material may also be identified by encountering a solid obstruction to passage of the stomach tube beyond the gastro- oesophageal junction.

Role of owner in decision making

Dealing with colic in horses can be an extremely emotive and distressing experience for owners. They can feel panicked into making decisions, which, on later reflection, they may regret.

Negative experiences from one horse can have a major impact on future decision making, such as assuming any future episodes will be critical, or that surgical cases always have an unsuccessful outcome. This may affect their willingness to have further investigations done on a horse presenting with colic, and may limit options for successful outcomes for future cases.

6 / 8 Figure 5. A small intestinal strangulation, demonstrating the multiple loops of distended small intestine, which may be palpable on rectal exam.

One study showed a decline in the number of horses undergoing surgical treatment for colic over a 10-year period16. In another study of horse owners’ knowledge and opinions of colic, many had a poor understanding of what colic is, what causes it and the different treatment options17. Participants in the survey wanted to make informed decisions and were keen for further information17,18.

Fact sheets, consent forms and educational materials can be helpful for owners, both during and after a colic episode, to understand the different processes, procedures, and their limitations.

A new initiative is establishing a series of educational materials for horse owners, including information on commonly performed diagnostic procedures. These will be freely available through the British Horse Society website for horse owners, but also for veterinary practitioners to download and use to support their client communications if they wish.

Ensuring the owner has an active, informed involvement in decision making is essential to improve the recognition, management and prevention of colic, and ensure the best options for each case can be considered fully.

References

1. Curtis L, Trewin I, England GC, Burford JH and Freeman SL (2015). Veterinary practitioners’ selection of diagnostic tests for the primary evaluation of colic in the horse, Veterinary Record Open 2(2): e000145. 2. Curtis L, Burford JH, Thomas JS, Curran ML, Bayes TC, England GC and Freeman SL (2015). Prospective study of the primary evaluation of 1016 horses with clinical signs of abdominal pain by veterinary practitioners, and the differentiation of critical and non-critical

7 / 8 cases, Acta Veterinaria Scandinavica 57: 69. 3. Freeman S (2004). Ultrasonography of the equine abdomen: techniques and normal findings, In Practice 24(4): 204-211. 4. Freeman SL and England GC (1999). Comparison of sedative effects of romifidine following intravenous, intramuscular, and sublingual administration to horses, American Journal of Veterinary Research 60(8): 954-959. 5. Freeman SL and England GC (2001). Effect of romifidine on gastrointestinal motility, assessed by transrectal ultrasonography, Equine Veterinary Journal 33(6): 570-576. 6. Southwood LL (2013). Practical Guide to Equine Colic, Wiley Blackwell, Chichester. 7. Dyce KM, Sack WO and Wensing CJG (2009). Textbook of Veterinary Anatomy (4th edn), Elsevier Health Sciences, St Louis. 8. Freeman SL (2002). Ultrasonography in the equine acute abdomen 2. Ultrasonography in the colic patient, In Practice 24(5): 262-273. 9. Klohnen, A, Vachon, AM and Fischer ATJ (1996). Use of diagnostic ultrasonography in horses with signs of acute abdominal pain, Journal of the American Veterinary Medical Association 209(9): 1,597-1,601. 10. Santschi EM, Slone DE Jr and Frank WM (1993). Use of ultrasound in horses for diagnosis of left dorsal displacement of the large colon and monitoring its nonsurgical correction, Veterinary Surgery 22(4): 281-284. 11. Dabareiner RM and White NA (1995). Large colon impaction in horses: 147 cases (1985-1991), Journal of the American Veterinary Medical Association 206(5): 679-685. 12. Cox R, Burden F, Gosden L, Proudman C, Trawford A and Pinchbeck G (2009). Case control study to investigate risk factors for impaction colic in donkeys in the UK, Preventive Veterinary Medicine 92(3): 179-187. 13. Jennings K, Curtis L, Burford J and Freeman S (2014). Prospective survey of veterinary practitioners’ primary assessment of equine colic: clinical features, diagnoses, and treatment of 120 cases of large colon impaction, BMC Veterinary Research 10: DOI: 10.1186/1746-6148-10-S1-S2. 14. Campbell ML, Colahan PC, Brown MP, Grandstedt ME and Peyton LC (1984). Cecal impaction in the horse, Journal of the American Veterinary Medical Association 184(8): 950-952. 15. Proudman CJ, Smith JE, Edwards GB and French NP (2002). Long-term survival of equine surgical colic cases. Part 2: modelling postoperative survival, Equine Veterinary Journal 34(5): 438-443. 16. Blikslager A and Mair T (2014). Trends in management of horses referred for evaluation of colic: 2004-2013. In Eleventh International Colic Research Symposium, Dublin, Ireland. 17. Bowden A, Brennan ML, England GCW, Burford JH and Freeman SL (2015). Colic: horse owner knowledge and experience, Equine Veterinary Journal 47(548): 4. 18. Freeman SL and Curtis L (2015). Developing best practice guidelines on equine colic, Veterinary Record 176(2): 38-40.

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