Colic in Horses: When is Surgery Necessary?

When a horse is in the midst of a bout of colic, many owners wonder if their animal will need surgery to fix the problem. For those owners who have never experienced a referral to an emergency medical clinic for surgery or intensive care, understanding their veterinarian's decision on how and where to treat the colic can be confusing.

During a presentation at the American Association of Equine Practitioners Focus on Colic Meeting, held July 24-26 in Indianapolis, Ind., Nathaniel A. White, DVM, MS, Dipl. ACVS, Jean Ellen Shehan Professor and Director at Virginia Tech's Marion duPont Scott Equine Medical Center in Leesburg Va., discussed what veterinarians look for when deciding whether to send a horse to a referral hospital for surgery and what factors might negate their decision to do so.

"Determining the need for referral or surgery for a horse with colic is usually made on an emergency basis," he began. "The decision is best based on a diagnosis; however, a specific diagnosis is not always possible, and the use of clinical signs is often necessary to make the decision."

White emphasized that no hard and fast rules dictate whether a horse will need surgery, and that each case should be "judged on its own merits based on the history and a thorough examination.

"The history and presentation may indicate the need for immediate surgical intervention without taking the time to process all the information from a complete colic examination," he added, as time is critical when recommending referral. Previous studies have shown that horses with a history of colic are at higher risk for more colic episodes.

White reviewed several common clinical signs associated with colic, and what they might indicate to a veterinarian deciding whether to send a horse to a referral hospital.

Pain

"Pain by itself, especially if severe and persistent or recurrent, is an indication for surgery," White explained. "This is particularly true if there is no response to analgesic administration."

That being said, White noted that with the introduction of equine pain killers such as flunixin meglumine (Banamine) and detomidine (Domosedan), veterinarians are able to use a horse's response to the analgesic to gauge whether he'll need surgery.

"Horses that have constant pain, particularly after an analgesic has been administered, are significantly more likely to need surgery," White explained. "Horses that have return of pain or those requiring a second or multiple administrations of an analgesic are also significantly more likely to need surgery."

White noted that the "timing of the response" to an analgesic is still vague; however, most veterinarians have determined through experience a rough response time to use as an indicator in their practice.

Horses with colic-associated pain that resolves with the administration of an analgesic and does not return can typically be managed medically rather than surgically.

White cautioned, however, that any recurring pain--no matter how insignificant it seems--could indicate the problem is not resolved.

"Any recurrence of pain should be considered a failure of resolution of the problem and, therefore, an indicator of increased odds that the condition will not respond to basic medical therapy and referral for further evaluation and monitoring is necessary," he concluded.

Additionally, White noted that in a few cases--such as with impactions in the large colon or sand colic--recurring pain can often be managed medically. However, even in these cases, surgery is a possibility if the pain remains for a long period of time or if there is no sign of improvement in intestinal motility.

Vital Signs

Although it might seem counterintuitive, a horse's vital signs likely won't dictate whether a veterinarian refers a horse for surgery, White explained.

He said temperature alone isn't generally a good indicator of whether a horse should be taken to surgery: "Rectal temperature is usually not increased in cases of acute strangulation or obstruction. Horses with enteritis or colitis, which do not require surgery, frequently have an increased rectal temperature, suggesting that surgery is contraindicated."

He noted veterinarians should also take into consideration vital signs such as heart rate, mucous membrane color, and capillary refill time in conjunction with other factors when deciding whether to take the horse to surgery.

"For example, heart rate can be misleading," White said. "Low, near normal heart rates can be observed early in very painful diseases. In this instance, pain should be considered the more important sign. High heart rates, though associated with severe diseases and poor survival rates, do not always indicate the need for surgery."

He noted, however, that "signs of cardiovascular compromise, such as increased heart rate, abnormal mucous membrane color, or poor mucous membrane refill, are evidence of disease requiring intensive medical management at a facility with the required expertise," but they don't necessarily indicate whether surgery is needed.

Gastric Reflux

Horses that have gastric reflux when colicking have about a 50/50 shot of requiring surgery. White explained that gastric reflux simply means the disease or condition causing the colic is blocking the small intestine, prohibiting ingesta and fluid from passing through the digestive tract. These cases can sometimes be managed medically, but depending on the location and severity of the obstruction, surgery is an option with some horses.

"Reflux can be caused by ileus (the inability of the intestine to function properly) or proximal enteritis (inflammation of the upper GI tract--more on that in a moment), which are most often treated medically and frequently require referral for appropriate medical management for fluid and electrolyte imbalances," White said.

He noted that colonic obstructions can sometimes be managed medically, as well.

"Because of the lack of sensitivity, other physical signs should be used in conjunction with gastric reflux to make a final determination about the need for surgery," he concluded, adding that a lack of gastric reflux doesn't necessarily mean the horse won't require surgery associated with the bout of colic.

Proximal Enteritis

"Proximal enteritis causes pain, gastric reflux, distended small intestine, and high peritoneal protein concentration, which together indicate a need for surgery," White said. "However, fever and subsequent depression are often observed, suggesting the signs are due to enteritis (which is typically managed medically)."

However, he added that if a veterinarian refers the horse for exploratory surgery to rule out a strangulation or obstruction, the procedure doesn't seem to decrease survival rates associated with the disease and instead ensures that a life-threatening problem is not present.

Decreased or Absent Gut Sounds

White explained that horses with decreased or nonexistent borborygmi (i.e., gut sounds) have "significantly increased odds of requiring surgery than horses with normal intestinal sounds." He added that if gut sounds remain absent or significantly decreased after the horse receives an analgesic, odds are the horse will require surgery to correct his ailment.

Rectal Exam Abnormalities

If a veterinarian finds something abnormal during a rectal examination of a colicking horse, it doesn't necessarily increase the probability the horse will require surgery, although numerous problems requiring surgical correction can be identified via a rectal exam.

Some typically medically corrected ailments that can be identified via rectal exam include colonic impactions and tympany (swelling due to intestinal gas accumulation).

Conditions that can be identified via rectal examination that generally require surgical correction include:

  • Inguinal (pertaining to the groin area) hernia;
  • Tight, multiple loops of small intestine;
  • Distended (bloated) and edematous (fluid-filled) colon;
  • Tight cecum filled with fluid ingesta; and
  • Excessive distention of any intestinal segment.

"If the findings on rectal examination are not normal, assessment of other clinical signs is necessary to make the decision about the need for surgery," White noted. "If there are no abdominal abnormalities during the first rectal examination, repeat examinations are indicated, particularly if other signs suggest a surgical disease."

Abdominal Ultrasound

Ultrasound is a valuable aid for diagnosing intestinal disease White explained, and in some cases veterinarians use abdominal ultrasounds to locate intestinal problems that can't be or simply aren't felt via rectal examination. Many issues found through an ultrasound require surgical correction. Some of these ailments include:

  • Intestinal distensions or entrapments;
  • Thickening of the walls of the large colon and large colon volvulus (twisting);
  • Inguinal hernia;
  • An entrapped colon;
  • Sand accumulations; and
  • Intussusception (where the intestine telescopes back onto itself) of the small intestine.

Abdominal Fluid Analysis

In some cases veterinarians will collect the horse's abdominal fluid seeking clues about whether a horse requires colic surgery. White explained that veterinarians take into account numerous factors in abdominal fluid that could suggest the need for surgery:

  • Protein Concentrations - White said increased protein concentrations alone generally point to a "simple obstruction" that can be managed medically.
  • White Blood Cell Count - An increased white blood cell count and a neutrophil (a type of white blood cell capable of engulfing and destroying bacteria and other disease agents) to monocyte (a type of white blood cell that converts into active macrophages, which specialize in fighting infections) ratio greater than or equal to 90% neutrophils usually indicate the horse has developed intestinal death or deterioration that's resulted in bacteria leakage; this ailment typically requires surgery.
  • Red Blood Cell Count - An increased white blood cell count generally points toward a bowel strangulation, which also requires surgery to repair.
  • Hemoglobin Concentrations - White explained that an increased hemoglobin concentration increases the likelihood the horse will need surgery.
  • Fluid Lactate Concentration - "Increased peritoneal fluid lactate concentration ... is also an indicator of intestinal compromise that indicates a surgical lesion," White explained. "Increasing lactate concentration from serial measurements also indicates progressive intestinal injury."

Essentially, he said, if any abnormal abdominal fluid is discovered, an intestinal problem is present that likely will require surgery.

Still Not Sure?

"When veterinarians are undecided because signs are confusing or suggestive but not convincing about the need for surgery, more in-depth evaluation or surgery will most likely be needed," White added. "The horse should be referred for a second opinion at a surgical facility where surgery or intensive medical management can be performed if needed.

"Though an analysis of the cost versus the benefits of referral has not been completed, a decision to refer early in the disease process will improve the chances of survival and often decrease the total cost of care by minimizing the incidence of postoperative complications," he concluded.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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