Colic Early Referral: Why It’s More Important Than Ever

Despite positive trends in colic surgery over the past 50 years, owners, referring veterinarians, and hospital-based surgeons are repeatedly reminded that the single most important factor impacting patient outcome is a prompt referral to a fully staffed and equipped surgical facility. Sadly, in recent years, the referral process seems to have shifted towards a delay in surgical treatment. Many factors could be responsible for this change, but owner issues, such as concerns about cost and misconceptions about the disease and its treatment, stand out.

Figure 1. When making a referral, the goal is to use diagnostic procedures that can identify those horses that do not need a referral for colic. This is not always realistic though. A more approachable goal may be to refer horses that need surgery at an earlier stage in the disease process. The downside to making a referral this early is that some horses may not need surgery. Image courtesy of Dr. David E. Freeman.

It is also time to refine the concept of early referral as sending a horse to a surgeon when available evidence tips the scale toward surgery, even when more solid proof is lacking (Figure 1), is often key to a successful outcome. Failure to do this leads to higher treatment costs, poor results, and a decline in confidence in colic surgery (Figure 2).

Importance Of Early Referral In Outcome

In a recent study on horses that had surgery for small intestinal strangulation, those that did not require resection (Figure 3) had superior long-term survival rates compared to those that required resection2 (Figure 4). In that study, all the horses that did not require resection survived until hospital discharge and experienced low complication rates. The median survival time for the group that did not require resection (when half the horses were still alive) was three years longer than the group requiring resection (120 months versus 84 months). This difference is significant. More importantly, those that did not need a resection (Figure 4) had a significantly shorter duration of colic before surgery than those that did need resection, evidence that referral before irreversible changes develop in the strangulated small intestine is a key element to improving survival after colic surgery.3 Early referral has been shown to improve survival after large colon volvulus (LCV),4,5 ileal impaction, 6 inguinal hernia,7,8, and entrapment in the epiploic foramen (EFE).9 The risk of postoperative ileus and diarrhea after surgery can also be reduced by early referral.10

Figure 2. Consequences of delayed referral, moving from left to right on the flowchart. This demonstrates that delays have consequences at the tissue level that can complicate patient outcome and increase the cost of treatment. Image courtesy of Dr. David E. Freeman.

The argument for early referral is strengthened by the observation that the length of small intestine strangled can increase over time as more is drawn in until the ileum becomes involved.11 (Figure 5). This can then lead to a more complicated surgery with a poorer prognosis. Delays in referral can also increase distention in the intestine oral to the lesion,12 which leads to poor perfusion of that segment and adhesions (Figure 5). Prolonged periods of pain can lead to self-inflicted traumatic injuries (Figure 6), and such findings could indicate a longer disease course preceding the time of discovery (Figure 6).

Owner Role – Different Than We Think

The owner’s decision regarding colic surgery is a complex part of the referral process,13 largely frustrated by the nature of the disease, limited opportunity for preparation, and the immediate need for resources that are not always available — such as a trailer for transport or funds — and limited opportunity to seek input from friends and family. If the owner states that surgery is not an option, the groundwork for failure has been laid in many cases. The problem is that a change of heart can follow when the need for surgery becomes established later, at which point the prospects of a successful outcome have passed, considerable expense has been incurred, and a resection that could have been avoided earlier is needed. Therefore, the referring veterinarian must have a frank and informed discussion with the owner about his or her aversion to colic surgery. Many owners might be seeking arguments against surgery at this stage, such as cost, poor outcomes, and other negative issues. They are likely grasping at the hope that surgery is not indicated.

The following are commonly used explanations from owners for rejecting surgery, which need to be addressed:

Figure 3. Strangulated small intestine in a horse that was referred before irreversible changes developed. This segment met intraoperative criteria, which led to the correct decision to not resect it. This resulted in a better outcome at a lower cost than if resection were required. Image courtesy of Dr. David E. Freeman.
  • Colic surgery is rarely successful. Colic surgery has a success rate of approximately 80% survival for horses with small intestinal strangulation.
  • The owner might prefer to try medical treatment first. Medical treatment is not a substitute for surgical treatment if the horse has a strangulating lesion, and prolonging suffering is inhumane.
  • A friend’s horse died from colic surgery, and he/she was devastated by the poor outcome. This experience reflects a strong emotional impact, but it is based on a single case, and each case is different.
  • The horse will never be the same after colic surgery. Most horses return to previous use, even in athletic competition at the highest level, such as winning major stakes races. A prime example is Lil E. Tee, an American-bred Thoroughbred horse that won the Kentucky Derby in 1992).
  • This mare is pregnant, and it will be impossible to save the mare and foal with surgery. Mares can foal normally and deliver a live foal at any time after colic surgery, provided the surgery is done promptly.
  • This is an old horse, and old horses do not handle anesthesia and colic surgery well. This is simply untrue (see the section on strangulating lipoma on page 9).
  • This horse is much loved/valued, but we cannot justify spending money on colic surgery in our present financial circumstances.

This is probably the most valid concern for some owners, but should be based on recognition of two critical factors: 1) if surgery is needed, the sooner it is done, the lower the cost, and 2) the attending veterinarian can seek help from a surgeon that could be consulted on the case for accurate estimates.

The cost of colic surgery can play a large role in an owner’s decision14 and could explain the growing rates of euthanasia, especially before and during surgery.15 Referring veterinarians can guide them on this.16 However, owner attitudes toward surgery can undergo a complete reversal from staunch refusal to full acceptance at all costs when the owner eventually realizes that surgery is the only option.

Figure 4. Survival curves show superior results for horses with small intestinal strangulation that did not need a resection (black) versus those that did (red), presumably because the former were referred sooner. All horses in the group that did not need a resection survived until discharge. Each downward step in a curve indicates death of one or more horses during that time period. Image courtesy of Dr. David E. Freeman.

If the owner declines the referral, the attending veterinarian must establish clear guidelines for the next step. At this point, the owner must be informed that if the horse has a true surgical lesion, especially small intestinal strangulation, only surgery will save its life. If a surgical diagnosis cannot be made definitively and if the horse “appears comfortable,” the owner might request continued medical treatment “just in case.”

This approach should prompt the following questions for the owner:

  • Can I afford repeated visits to the farm for treatments?
  • Is this a humane approach?
  • What is my true financial limit on this horse?
  • How much time can I commit to around-the-clock monitoring and care?
  • Can I handle watching my horse suffer?
  • How much time can I commit to around-the-clock monitoring and care?
  • Can I handle watching my horse suffer?
  • Is my family supportive of this decision?
  • Will I change my mind or stay the course?

The last question is critical because if the owner requests surgery at a later period, it is probably too late. Resources have been exhausted, and euthanasia may be the only reasonable option. At that point, the cost of surgery will be considerable, and the outcome for the patient is poor (Figure 7). Referral to a hospital for a second opinion and supportive care is another option and could confirm that humane euthanasia is needed.

Diagnostic Challenges

Horses that require surgery or euthanasia because of a surgical lesion can have one or more of the following: persistent pain despite analgesic drugs, a persistently elevated or increasing heart rate (≥ 48 beats/minute), reflux from a nasogastric tube, worsening abdominal distention, abnormal rectal examination findings, obvious abnormality on ultrasound examination, and belonging to a high-risk group (see below). However, pain indicators in some horses might be absent or subtle, such as nostril tension and flare, facial grimace, and abrasions on boney prominences. The diagnostic approach should be realistic and recognize that a high degree of diagnostic sensitivity is preferred to seeking a high degree of diagnostic specificity17 (Figure 1). High sensitivity means that many horses that could be treated at home will be referred, which is better than the aggressive pursuit of diagnostic accuracy that could delay referral for horses with surgical lesions. This is the error that leads to the worst patient outcomes.

Figure 5. Fluid distribution between strangulated and proximal intestine (green). This demonstrates that fluid builds up in the entrapped segment (black). The entrapped segment draws unobstructed distal intestine into the entrapment to accommodate the growing fluid buildup until the ileum is reached. Obstruction in the strangulated segment then leads to severe obstruction and distention of the proximal segment (green). This illustrates how delayed referral can increase the length of strangulated intestine. Image courtesy of Dr. David E. Freeman.
Figure 6. Abrasions on facial boney prominences consistent with colic of some duration. This symptom is especially important if evident when the horse is first discovered with colic. This finding might expedite the decision to refer.
Image courtesy of Dr. David E. Freeman.

Risk Factors In Diagnosis

Simple features in the signalment can provide diagnostic clues for different surgical lesions (Table 1). If other findings fit with the possible “at risk” diagnosis, as with lipoma (see below), the odds of that disease being responsible for colic increase accordingly. This should prompt an early decision toward surgery. However, as with any diagnostic procedure, it is important not to fixate on any particular diagnosis.

Strangulating Lipoma

Old horses (horses ≥ 10 years) have similar types of colic as younger mature horses, but they also have their own more lethal and common disease: strangulating lipoma.18 This age/disease link is so well established as a horse ages18 that an old horse with colic should be considered as having a strangulating lipoma until proven otherwise.

Figure 7. Example of severe necrosis and peritonitis in strangulated small intestine after the owner initially declined surgery, but then opted for surgery. Too much time had passed, and surgery was not a reasonable option. Image courtesy of Dr. David E. Freeman.

Unfortunately, these horses are the most likely victims of delayed decisions about surgery. They are already at the end of their lifespan, and many of them have comorbidities, like lameness, pituitary pars intermedia dysfunction, and laminitis, that might tip the decision against surgery. Many have earned a strong degree of emotional worth but have passed their prime for their intended purpose. This is the group that presents the greatest financial challenge to owners. If distended loops of small intestine are found on rectal examination or on ultrasound examination with abrasions on bony prominences.

(Figure 6), with or without reflux through a nasogastric tube, surgery is probably required as soon as possible.

Old horses are likely to be denied surgery because of the myth that they cannot handle anesthesia and surgery well.19 Old horses can be stoic,19 which can be a breed effect, as commonly seen in Tennessee Walking Horses, but all horses with a strangulating lesion can also become obtunded by endotoxemia. This can lead to an impression of a mild or resolving disease. As with all horses with small intestinal strangulation, these horses also develop a vacuum-packed large colon, which can feel like a dry, hard impaction on palpation per rectum. This creates the erroneous impression that they have a large colon impaction, a nonsurgical disease. A rectal finding of colon impaction is actually a strong indicator that small intestinal strangulation is the primary lesion.

Table 1. Risk factors for surgical diseases that could help with diagnosis.

Horse Factor(s)At Risk For:
Horse >10 years old (especially >15)Strangulating lipoma
Intact male (especially Standardbreds)Inguinal hernia
Miniature horse, small pony, foal of any breedFecalith in small colon
Mare in late pregnancyUterine torsion
Previous small intestinal surgeryRecurrent disease or adhesions
Postpartum mare with severe abdominal painLarge colon volvulus, other strangulation
Postpartum mare with mild colic, peritonitisSmall colon avulsion/necrosis, ruptured uterus
Feeding coastal Bermuda grass hayIleal impaction
Cribber (especially a Thoroughbred and gelding)Epiploic foramen entrapment


Peritoneal fluid changes, such as serosanguinous discoloration and elevated peritoneal lactate, develop early in the course of intestinal ischemia.20 Although easy to perform, abdominocentesis performed at home delays referral and increases cost with little gain. Abdominocentesis can also be difficult to interpret, and equivocal findings are common. These findings should not be interpreted in isolation. Abdominocentesis might have a place in a patient’s treatment plan if the owner needs strong guidance on a decision for euthanasia. The following limitations should be considered before using this test:

Figure 8. Although a clear sample of peritoneal fluid like this would make a strangulating lesion unlikely, strangulation and other severe diseases, including large colon volvulus and ruptured viscus, cannot be ruled out based on inspection only. Image courtesy of Dr. David E. Freeman.
  • Gross appearance, PCV, and TP in the peritoneal fluid can be misleading or equivocal and time for laboratory analyses can delay decision-making (Figure 8).
  • The following surgical lesions might not develop diagnostic peritoneal fluid changes:
    • Large colon volvulus, even with a nonviable colon
    • Diaphragmatic hernia (strangulated segment in the thorax)
    • Early pressure necrosis in the site of an enterolith, fecalith, or foreign body impaction
    • Lipoma strangulation by the wrapping of the lipoma around a segment of intestine rather than strangulating a loop and its vasculature

Reassessment Of Iv Fluid Therapy

The misconception has emerged over recent years that fluid therapy on the farm for horses with strangulating diseases can make them better candidates for surgery and anesthesia. The ready availability of sterile fluids in plastic bags and associated systems for delivery make this treatment very feasible and attractive (Figure 9). However, the benefits of this approach before referral are highly questionable, even for strangulating lesions, and the delays, complications, and costs associated with it are difficult to justify. Similar concerns apply to continuous rate infusions (CRIs) on the farm (e.g. lidocaine). Instituting IV fluids immediately before surgery is sufficient in most cases because definitive treatment (surgery) follows.

Risks of overly aggressive fluid therapy before referral are:

Figure 9. Although highly effective systems for delivery of sterile physiological fluids exist for horses with colic, fluid therapy on the farm or in a small nonsurgical hospital only delays referral, accomplishes little, and might even be harmful. Image courtesy of Dr. David E. Freeman.
  • High-volume fluid therapy can produce a misleading degree of improvement that only confuses owners and delays referral.
  • High-volume fluid therapy can create electrolyte imbalances such as calcium and magnesium losses through sodium diuresis.22 Some of these changes can delay postoperative recovery and reduce survival.
  • The time required for administration of fluids and to monitor responses allows for the worsening of tissue injury (Figure 2). Consequently, the ischemic changes can become irreversible and the more proximal distended segments will probably fill with much of the fluid-infused IV (Figure 5). This only adds to proximal intestinal distention and mural edema, critical factors that increase pain and delay recovery.23
  • There is a growing awareness that aggressive fluid therapy can cause adverse consequences for recovery of intestinal function. This can be mediated through damage to the vascular endothelium that exacerbates transcapillary fluid leakage and tissue edema.24
  • In a clinical study in horses with small intestinal strangulation, a more restricted goal-directed approach to fluid therapy had similar survival and complication rates as the traditional liberal fluid therapy.25

Treatments And Diagnostic Procedures Repeated At The Hospital

Repeating the same diagnostic and treatment procedures at a surgery facility that were performed at the farm can become a contentious issue with many owners, and referring veterinarians should consider this. Owners regard this as an unnecessary additional cost, arguing that their veterinarian already did the same. Unfortunately, some information might be missing, or some indicators could have changed during the interim. Warning owners of this beforehand might prepare them to accept this necessity. If hospital tests are regarded as necessary in the field situation, then the horse should be referred instead so that the procedure can be performed in the same hospital that will conduct the surgery.


Decision-making about colic referral is complicated for owners,13 and therefore a team approach is recommended, that starts with the owner or designee and the referring veterinarian. If clinical signs suggest surgical treatment is indicated, but owner reluctance persists, a surgeon at the hospital that would receive the case should be consulted to provide a reasonable overview of cost and prognosis. The decision that surgery is or is not an option should be based on solid facts that could be produced by discussion with all involved. The goal is not to change the owner’s mind but to prevent a fatal change of course that closes off the opportunity for a successful surgery.


The referral process can be summarized as the need to pursue a second opinion for a horse that does not fit within the typical colic presentation that will respond to medical treatment at home. The owner should be guided by accurate information as to the true range of costs for the suspected disease and based on consultation with a surgeon at the hospital. This is intended to prevent those problem situations in which the surgery option is rejected initially, only to be selected later when the nonsurgical approach is failing. Owner education is critical, and all veterinary professionals play a role in that duty. This approach is based on a refined concept of early referral, which is sending a horse to a surgeon in a timeframe from disease onset that produces the best outcome at the lowest total cost (Figure 2).


1. Proudman CJ, Dugdale AHA, Senior JM, Edwards GB, Smith JE, Leuwer ML, French NP. Pre-operative and anesthesia-related risk factors for mortality in equine colic cases. Vet J 2006;171:89-97.

2. Rudnick MJ, Denagamage TN, Freeman DE. Effects of age, disease and anastomosis on short- and long-term survival after surgical correction of small intestinal strangulating diseases in 89 horses. Equine Vet J. 2022 Jan 12. doi: 10.1111/ evj.13558. Epub ahead of print. PMID: 35023209.

3. Freeman DE, Hammock P, Baker GJ, Foreman JH, Schaeffer DJ, Richter RA, Inoue O, Magid JH. Short- and long-term survival and prevalence of postoperative ileus after small intestinal surgery in the horse. Equine Vet J Suppl. 2000;32:42-51.

3. Freeman DE, Hammock P, Baker GJ, Foreman JH, Schaeffer DJ, Richter RA, Inoue O, Magid JH. Short- and long-term survival and prevalence of postoperative ileus after small intestinal surgery in the horse. Equine Vet J Suppl. 2000;32:42-51.

4. Levi O, Affolter VK, Benak J, Kass PH, Le Jeune SS. Use of pelvic flexure biopsy scores to predict short-term survival after large colon volvulus. Vet Surg 2012;41:582-588.

5. Hackett ES, Embertson RM, Hopper SA, Woodie JB, Ruggles AJ Duration of disease influences survival to discharge of Thoroughbred mares with surgically treated large colon volvulus. Equine Vet J 2015;47:650-654.

6. Parks AH, Doran RE, White NA, et al. Ileal impaction in the horse: 75 cases. Cornell Vet 1989;79:83-91.

7. Baranková K, M. de Bont MP, Simon O, Meulyzer M, Boussauw B, Vandenberghe F and Wilderjans H. Nonsurgical manual reduction of indirect inguinal hernias in 89 adult stallions. Equine Vet Educ 2021; https://doi: 10.1111/ eve.13494.

8. François I, Lepage O, Boswell J, Schofield W, Perez Olmos JF, Grulke S. Acquired inguinal herniation in horses: a retrospective multicenter study of 48 cases. Vet Surg. 2014;43:E167.

9. Scheidemann W. Beitrag zur Diagnostik und Therapie der Kolik des Pferdes: Die Hernia Foraminis omentalis. 1989; DMV thesis, Muenchen.

10. Fogle CA, Gerard MP, Correa M and Blikslager AT. An analysis of factors associated with a prolonged duration of colic (344 horses). Proc. 10th Equine Colic Res. Symp. 2011;10, 202.

11. Gandini M. and Giusto G. Why is the ileum involved in the majority of cases of internal hernias? a biomechanical hypothesis. Equine Vet Educ 2021;33. Supplement 12:48.

12. Dabareiner RM, Sullins KE, Snyder JR, White NA 2nd, Gardner IA. Evaluation of the microcirculation of the equine small intestine after intraluminal distention and subsequent decompression. Am J Vet Res. 1993;54:1673-1682.

13. Scantlebury CE, Perkins E, Pinchbeck GL, et al. Could it be colic? Horse-owner decision making and practices in response to equine colic. BMC Vet Res 2014; doi: 10.1186/1746-614810-S1-S1.

14. Archer DC. Colic surgery: keeping it affordable for horse owners. Vet Rec. 2019;185505-507.

15. Blikslager AT, Mair TS. Trends in the management of horses referred for evaluation of colic: 2004–2017. Equine Vet Educ 2021;33:192-197.

16. Ireland JL, Clegg PD, McGowan CM, et al. Factors associated with mortality of geriatric horses in the United Kingdom. Prev Vet Med 2011;101:204– 218.

17. Peloso JG, Cohen ND, Taylor TS, Gayle JM. When to send a horse with signs of colic: is it surgical, or is it referable? A survey of the opinions of 117 equine veterinary specialists. Proc Am Assoc Eq Pract 1996;42:250-253.

18. Freeman DE, Schaeffer DJ. Age distribution of horses with strangulation of the small intestine by a lipoma or in the epiploic foramen: 46 cases (1994-2000). JAVMA 2001;219:87-89.

19. Southwood LL, Gassert T, Lindborg S. Colic in geriatric compared to mature nongeriatric horses. Part 2: Treatment, diagnosis and short-term survival. Eq Vet J 2010;42:628-635.

20. Ruggles AJ, Freeman DE, Acland HM, et al. Changes in fluid composition on the serosal surface of jejunum and small colon subjected to venous strangulation obstruction in ponies. Am J Vet Res 1993;54:333-340.

21. Pratt SM, Hassel DM, Drake C, Snyder JR. Clinical characteristics of horses with gastrointestinal ruptures revealed during initial diagnostic evaluation: 149 cases (1990-2002). Proc Am Assoc Eq Pract 2003;42:254-255.

22. Garcia-Lopez JM, Provost PJ, Rush JE, Zicker SC, Burmaster H, Freeman LM. Prevalence and prognostic importance of hypomagnesemia and hypocalcemia in horses that have colic surgery. Am J Vet Res 2001;62:7-12.

23. Shah SK, Uray KS, Stewart RH, Laine GA, Cox CS Jr. Resuscitation-induced intestinal edema and related dysfunction: State of the science. J Surg Res 2011;166:120130.

24. Woodcock TE, Woodcock TM. Revised Starling equation and the glycocalyx model of transvascular fluid exchange: an improved paradigm for prescribing intravenous fluid therapy. Br J Anaesth 2012;108:384-394.

25. Giusto G, Vercelli C, Gandini M. Comparison of liberal and goal-directed fluid therapy after small intestinal surgery for strangulating lesions in horses. Vet Rec. 2021 Feb;188(3):e5. doi: 10.1002/vetr.5. PMID: 34651880.

David E. Freeman, MVB, PhD, Diplomate ACVS

David Freeman graduated from the Veterinary College of Ireland, Dublin, in 1972 and was awarded a PhD from the University of Pennsylvania in 1985. From 1981 to 1994, he was an equine surgeon at New Bolton Center and became a board-certified surgeon in the American College of Veterinary Surgeons in 1989. He joined the faculty at the University of Illinois, College of Veterinary Medicine in 1994 and became the head of equine medicine and surgery in 1998. In 2004, he joined the department of large animal clinical sciences at the University of Florida, College of Veterinary Medicine, as a professor of equine surgery and associate chief of staff, and subsequently served as the service chief in large animal surgery. He was also the interim department chair in large animal clinical sciences at the University of Florida from 2009 to 2012.