History of Colic Surgery and a Look to the Future

An overview of colic surgery over the last 40 years suggests improvements in outcome, largely a result of early diagnosis and referral, allowing horses to arrive at referral hospitals in better overall systemic condition, as compared to years past. However, closer inspection of information from different sources suggests that postoperative complications are increasing and long-term survival rates could improve further. The growing emphasis on postoperative treatment could divert our attention from surgical steps that are critical to improving outcome. Author’s address: University of Florida, College of Veterinary Medicine, Department of Large Animal Clinical Sciences, PO Box 100136, Gainesville, FL 32610-0136; e-mail: freemand@ufl.edu.

1. Introduction

The purpose of this presentation is to review progress made in the last 40 years of colic surgery, to determine where progress has been made, and with a look to the future, determine what further can be done to improve outcomes. Although most practitioners may feel that colic surgery is of little relevance to their daily activities, their role in improving survival and reducing complication rates is critical. They are the most important members of the team involved in saving the horse’s life at critical steps in the process, the early stages of the disease process, when the need for referral should be recognized, and the later stages, during management of life-threatening postoperative complications. They also serve as a critical liaison with the owner, who will seek their guidance when the horse is hospitalized and after it returns home following surgery. Such guidance can only be provided by a practitioner who is well-informed about all the intermediate steps that pass from the time of referral to the day the horse leaves the hospital. 

2. Short-Term Survival Rates—Early Studies

Although colic surgery was commonplace in university hospitals in the early 1970s, veterinarians and owners viewed it largely as a last resort, a prologue to an imminent death. A 1971 paper described a successful outcome in 10 of 38 horses (26%) with colic treated by surgery, and most survivors had a minor intestinal procedure.¹ Authors of this study concluded that, “although the overall recovery rate was low, the procedure is entirely justified if only as a means of diagnosis.”¹ A review of cases from the University of California from 1958 to 1971 reported a mortality rate of 72.9% in 48 horses that had surgery for a small intestinal strangulation.² However, the mortality rate dropped to 46.6% in the last 14 years of the review period, which is evidence of improvement in management of these cases.²

In studies spanning a period from 1970 to 1984, Professor Barrie Edwards and Judith Hunt described complications of colic surgery and their impact on survival in 215 horses that recovered from general anesthesia.^3,4 Of the small intestinal cases, 55% survived compared with 68% in the large intestinal cases.^3,4 A report by Professor Huskamp from his private practice hospital in Germany reviewed 613 horses in which colic surgery was completed from 1979 to 1981.⁵ He reported 87.7% short-term survival (alive at discharge from the hospital) for small and large intestinal lesions.⁵

3. Short-Term Survival Rates—Recent Studies

Recent retrospective studies on short-term survival rates in horses after colic surgery suggest that more than 80% of horses that recover from anesthesia after small intestinal surgery are discharged from the hospital.⁶ This is the most challenging of of surgeries that we do and traditionally is associated with a poorer prognosis than other procedures. These numbers appear to be superior to earlier publications and have been attributed to improvements in surgery and anesthesia. A more likely explanation is a more positive attitude from owners and referring veterinarians, leading to prompt referral that places the horse in the hospital when it is an excellent candidate for surgery and anesthesia. Another important contributing factor to this improved attitude towards colic surgery was an apparent increased prevalence of nonstrangulating displacements of the colon, which did not appear to be commonplace before 1977.^7-9 This cases did much to enhance the reputation of colic surgery because they have an excellent prognosis for complete recovery.⁹

Although it is difficult to measure the effect of early referral on outcome, the lower reflux volume, packed cell volume (PCV), and heart rate, and higher total leukocyte count at presentation in horses admitted to one hospital after 1980 compared with previous admissions provide evidence of a trend towards earlier referral.¹⁰ In accordance with this, the study demonstrated a trend towards improved survival rates in horses that had surgery towards the end of the study period compared with the beginning¹⁰ (Table 1). Also, there is recent evidence that some strangulated small intestinal segments can be viable and not require resection, presumably because surgery was performed early in the disease course (Fig. 1). These horses can have superior short-term and long-term survival rates compared with horses treated with resection and anastomosis.^11,12 Such cases could be the beneficiaries of early referral, allowing surgery to be performed before irreversible intestinal damage has developed. The risk of complications can also be reduced by early referral, as the risk for postoperative ileus (POI) after strangulating lesions and diarrhea after nonstrangulating lesions appears to increase with duration of colic.¹³

A comparison between present and past success rates with surgical treatment of colic suggests a considerable improvement, but this assessment needs to be tempered with caution. Firstly, survival rates reported by Professor Huskamp for small intestinal lesions treated between 1979 and 1981 were comparable to those reported today.⁵ Secondly, most horses with strangulating lesions in the 1970s typically arrived at a veterinary hospital with more severe endotoxemic shock and more profuse reflux than many of our patients today.^2-4,10 Surgery was more complicated in the 1970s because the ischemic changes were more advanced and had progressed throughout a long segment of intestine. 
 

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